TECHNICAL LIBRARY *

JOURNAL OF THE

AMERICAN SOCIETY

OF

SUGAR BEET TECHNOLOGISTS

VOL. 19, NO. 1 MARCH 1976

J O U R N A L

of the

American Society of Sugar

Beet Technologists

Volume 19 Number 1

March 1976

Published semi-annually by

American Society of Sugar Beet Technologists

Office of the Secretary

P.O. Box 1546

Fort Collins, Colorado 80522

Subscriptioti prices:

S4.50 per year, domestic $5.00 per year, foreign $2.50 per copy, domestic $2.00 copy, foreign

Made in the United States of America

T A B L E O F C O N T E N T S Title Author Page

President's Address Hugh G. Rounds 1

Seed-borne Phoma betae as influenced by area of sugarbeet production, seed processing and fungicidal seed L. D. Leach Treatments J. D. Mac Donald 4

Feeding preference and reproduction of the beet leafhopper on two Russian A. C. Magyarosy Thistle plant species /. E. Duffus 16

Sugarbeet storage rot in the Red River W. M. Bugbee Valley, 1974-75 D. F. Cole 19

Breeding sugarbeet for resistance John O. Gaskill to Yellow Wilt Roberto Ehrenfeld K 25

The effect of sterile cytoplasm on J. C. Thearer curly top disease resistance D. L. Mumford 45

Effects of early terminal irrigation and late nitrogen application on C. F. Ehlig yield and incidence of root rot R. D. LeMert in sugarbects in the Imperial R. Y. Reynoso Valley O.K. Arterberry 49

Climatic periods and thresholds K. James Fornstrom Important to sugarbeet production Larry O. Pochop 55

A growing mulch tillage system to reduce K. James Fornstrom wind erosion losses of sugarbeets Rex D. Boehnke 65

Cultivar blends for buffering against curly top and leafs pot diseases of sugarbeet Ralph E. Finkner 74

Meritorious Service Awards 83

It's Our Move

H U G H G. R O U N D S , PRESIDENT T h e Amer ican Society of Sugarbeet Technologis ts

Several unprecendented "happenings" during the past two years have vaulted this period into a milestone era in the history of the beet sugar industry. Several occurrences should be explored in the light of their importance to the future of the industry.

In 1974 the Congress, at the expiration of the Sugar Act, failed to enact legislation which would extend the life of the old Act or pro-vide a new act. This was unfortunate, for the principles of this act, though varying in detail down through the years, provided a protective umbrella to the processor, grower, and the consumer. But the industry was unable to influence the Congress to keep the Act. Further-more, certain elements spoke out in favor of replacing sugarbeets with other food crops.

The volatility of the sugar market in recent months attests to the effectiveness of the Act. Where prices fluctuated in terms of dimes and quarters under the Act, they now change in terms of dollars.

Sugar prices spiraled to unprecendented highs in 1974 caused by a world shortage of sugar. The demise of the Sugar Act was untimely; the nation found itself looking to the "have" nations for raw sugar supplies in a manner not unlike that of the oil supplying nations. But the major result was that the use of sugar dropped significantly. Con-sumers either chose to reduce their intake of sweet foods and bevera-ges, or they turned to products containing sugar substitutes. It is doubtful that sugar will ever again reach the per capita level of 100 lbs.

The sugar shortage and spiraling prices focused attention on several sugar substitutes. Notable among these is high fructose corn syrup. Long an active competitor in the sweetener market, the corn processing industry can now offer a syrup for commercial use com-parable in sweetness to our own sugar syrups, but costing less under today's conditions. It is estimated that annual production of high fruc-tose corn syrup will reach the equivalent of 48 million cwt. sugar by 1978 year end. Moreover, waiting in the wings are several synthetic sweeteners moving to take their share of the sweetener market. Sugar is assured of vigorous competition in the future.

For a number of years strenuous efforts have been made and millions of dollars spent by our industry in complying with schedules and regulations of the regulatory agencies — primarily the FDA, OSHA, and EPA. The importance of complying with the laws of the land has never been underemphasized. Yet, in December of 1974,

2 JOURNAL OF THE A. S. S. B. T.

the industry received a severe jolt when a number of our member com-panies were indicted by Federal Grand Jury for alleged violations of an antitrust law during the period through 1972. Since December, 1974, a number of private suits, most of which are alleged to be class actions, have been filed against most of our member companies and national grower associations. In each of these cases, plaintiffs allege certain violations of the antitrust laws and seek treble damages in an unspeci-fied, undetermined, but substantial amount.

While the Society has not been involved in these antitrust matters, this industry and all members of our Society must carefully examine all inter-company exchanges, including technical, whether in the form of letters, reports, research papers, or dialogue. Unfortunately, this strikes at the very roots of this Society and the Beet Sugar Develop-ment Foundation, both of which have been instrumental in bringing the industry to its present level of technical competence. In this regard, we can all profit by the utilization of competent attorneys skilled in antitrust law.

So, in reviewing the two years since we last met, it appears that we did not win friends nor influence people. We witnessed the demise of the Sugar Act; we profited from excessively high sugar prices, but now face a loss in sales and suffer competition from sugar substitutes; the long range need for the sugarbeet crop was officially questioned in view of expected world food shortages; and, last but not least, a num-ber of processors were indicted. It was truly an epic period.

Couple all this with our ever-increasing costs and urgent energy-related problems, and the future of our industry may not appear exactly luminous.

At this point, however, our position must not be one of discourage-ment and despair. Now is the time for a re-evaluation of our goals and rededication of ourselves to changing the outlook. Fortunately, we have some strong points going for us.

First, let me emphasize the fact that we are involved in an en-deavor basic to Man's survival — the production of food, and sugar is without questions an important energy-giving food.

Second, our industry was founded and has been maintained by dedicated and skilled people at every level from sugarbeet growers to company management, technicians, and staff personnel. They are our front line in meeting the challenge of the future. But let us not over-look the many significant contributions of the state and federal agri-cultural scientists located at universities, laboratories, and agricultural stations. They, too, are a dedicated group and an important segment of our industry.

Our salvation will be the creativity and innovation that can and must be brought to bear by all of our people on the serious problems confronting this industry. Let me list what I feel are priority problem areas in need of prompt consideration:

VOL. 19, No. 1, MARCH 1976 3

a. Sugarbeets possess the greatest potential energy output of any crop known. Yet, after refining, the food calorie out-put per fuel calorie input is 1:1 or lower, whereas most U.S. field crops yield about 2:1.* The need for our technical forces to set about improving this ratio is urgent.

b. We are in dire need of sound planning and legal guidelines from Management.

c. Seed improvement capable of significantly increasing sugar per acre, new acceptable and effective insecticides and herbicides along with improved cul tura l practices — all aimed at making sugarbeets more competi t ive — these must receive renewed a t ten t ion from the agri-cultural scientists.

d. New processing methods must be developed, automated, and accepted into the factories to improve sugar recovery.

e. The search for new uses for our sugar and by-products must be intensified.

f. New- aggressive marketing techniques must successfully meet a less stable pricing situation and the compet i t ion of new sweeteners.

All of these things and more must be accomplished with due regard to the laws of the land.

The beet sugar industry has successfully maintained its position over the years on dedication, creativity, and innovation. Now is the time to bring these attributes to bear again, not only on today's problems, but also on the challenge of the future. To do otherwise is to invite senility and all its ramifications for the industry.

It's our move.

*Rcf. Kastens, M.L., Chemtech, 5, 675 (1975).

Seed-borne Phoma betae as Influenced by Area of Sugarbeet Production, Seed

Processing and Fungicidal Seed Treatments

L. D. L E A C H and J . D. M A C D O N A L D 1

Received for publication December 19, 1975

Introduction The only important seed-borne pathogen of sugarbeet seedlings is

Phoma betae (Oud.) Fr., [=Pleospora bjoerlingii By ford.] . Other seedling diseases are caused by soil inhabiting fungi such as: Aphanomyces cochlioides Drechs., Pythium ultimum Trow, P. debaryanum Hesse, P. aphanidermatum (Edson) Fitzp. or Rhizoctonia solani Kuhn [=Thanatephorus cucumeris (Frank) Donk.]

In Europe, the excellent survey by Dunning (6)2 in 1972 showed that plant pathologists in 13 countries believed that the most important seedling pathogen of sugarbeets was Phoma betae and that seed treat-ments effective against this pathogen were indispensible. In the United States, however, our experience has been less consistent. Prior to the 1930s when most of our seed was imported from Europe, Phoma seedling disease was quite serious and mercury seed treatments were commonly used as the only effective means of control. With the initia-tion of domestic seed production in the arid southwest, sugarbeet seed was found to be essentially free from Phoma (8, 9), thus allowing attention to be focused on the soil-borne seedling pathogens. The use of mercury seed treatments was discontinued and newer, often selec-tive fungicidal seed treatments were substituted to protect seedlings against the other pathogens. However, when domestic seed produc-tion was later shifted to Oregon for the production of non-bolting varieties, some seed lots were again found to carry considerable Phoma (10). This was cause for some concern as the protective seed treatments which had come into use were only partially effective against Phoma and the industry preferred not to return to the use of mercury treat-ments.

1Professor Emeritus and Research Assistant, respectively, Department of Plant Pathology, Uni-versity of California, Davis, CA95616. The writers thank Carol Frate, research assistant, for help with part of the laboratory and greenhouse trials; A. A. Mast, Western Seed Production Company, Phoenix, Arizona, Sam Campbell, West Coast Beet Seed Co., Salem, Oregon, Frank R. Low, British Columbia Sugar Refining Company, Vancouver, B. C, and C. K. Comerford, Irish Sugar Co., Dublin, Ireland for seed samples from Oregon, Arizona, British Columbia and Europe, respectively; and the California Sugarbeet Growers and Processors for financial assistance.

'Numbers in parentheses refer to literature cited.

VOL. 19, No. 1, MARCH 1976 5

In Oregon, the seed crops are planted in August or early Sep-tember and sprinkler-irrigated until the fall rains begin. Phoma first appears to a limited extent in the fall, as seedling or leaf spot infec-tions, and persists through the winter as infections on leaf or crown tissue. With spring growth and bolting, leaf spots, crown infections, and later, lesions on the seed stalks appear. During periods of rainfall or high humidity, pycnidia of the fungus exude spores in gelatinous masses. These spores are readily spread by splashing rain or overhead sprinklers or, when dry, may become air-borne and by these means come into contact with developing floral parts and result in seed infection. The most important period in terms of seed infection, how-ever, appears to occur during the harvest period. When the seed is ready to harvest, the seed stalks are cut, swathed and allowed to cure in the field for a period of 10 to 20 days before the actual threshing of the seed. If rainfall occurs during this period it further stimulates sporula-tion of the pycnidia and easily spreads Phoma spores to the seed where they may germinate and invade tissues of the seed units.

Because Phoma again appeared to be becoming a problem, and since the earlier work with seed-borne Phoma had involved European or the older domestic multigerm varieties, it was felt that a re-evaluation of the Phoma problem was desirable using cur rent monogerm seed. The objectives of this study were to identify the climatic factors associated with seed infection, to determine the effects of commercial seed processing on the levels of seed transmission, and to compare the effectiveness of protective fungicidal seed treatments on seed lots with different levels of infestation.

Determination of Seed Infection Evaluation of the amount of Phoma carried on beet seed was

determined by both laboratory and greenhouse trials. There are three general laboratory methods for determining the percentage of seeds carrying Phoma.

1. Blotter method — Blotters of the type used in determinations of seed germination are soaked, drained and placed in petri dishes. Five seed units are placed in each dish and incubated for 7 days at 20°C with a cycle of 12 hours of darkness and 12 hours of near ultraviolet light. After incubation the seeds and seedlings are examined with enlarge-ment of 20 to 50 times for pycnidia of P. hetae.

2. Potato dextrose agar method — PDA is poured into petri dishes at approximately 15 ml per dish. Five seed units are placed in each dish, incubated for 7 days at 20° in a cycle o f l 2 hours darkness and 12 hours of near ultraviolet light. After incubation, all seeds, seedlings and fungal colonies are examined at 20-50X magnification for pycnidia of P. hetae. Seed analysts usually prefer the PDA method because it is less time consuming with large numbers of samples. Unfortunately, with

6 JOURNAL of THE A. S. S. B. T.

some seed lots, contaminating saprophytic fungi may seriously inter-fere with accurate identification.

3. Water agar method — Water agar (1.2%) is poured into plastic petri dishes in a shallow layer. Five to 7 seed units are placed in each dish and incubated for 7 clays at 20CC. The dishes are inverted and examined at the level of agar contact with the bottom of the dish for the presence of "holdfasts" as described by Mangan (11, 12). Magnification of 50-100 times is used for observation. To retard seed germination 50 ppm of 2,4-D may be added to the water agar (12). Bugbee (1) recently reported that the use of a selective medium containing boron induced the holdfasts to turn dark brown to black so they could be observed with the naked eye or a 10X hand lens.

The water agar method usually gives the highest readings, espe-cially in the presence of contaminating fungi, and for this reason was felt the most desirable for use in this study. Additional information on seed infection can be secured with either the PDA or water agar methods by pretreating part of the seeds from each lot in NaOCl. A pretreatment consisting of a 5-minute immersion in 0.5% NaOCl was used throughout this study, although European workers favor 10-minute treatments in 1.0% solutions for more heavily contaminated seed. Examination of seeds plated without disinfestation indicates the total number contaminated by Phoma, while similar observations of disinfested seeds indicate the amount of deep penetration of Phoma into the seed tissues. In the present study, 50 seeds from each seed sample were plated on water agar following disinfestation, and 50 were plated without disinfestation.

The ability of seed-borne Phoma to infect seedlings was studied in a series of greenhouse trials, where 150 untreated seeds from each sample were planted in moist pasteurized soil and maintained in growth chambers at approximately 12°C for 28 days. Young seedlings which exhibited damping-off symptoms were removed from the soil, plated on water agar and observed for the characteristic holdfasts to confirm Phoma infection. At the end of the experiment all seedlings were lifted, washed, and examined for lesions on root or hypocotyl tissue. All seedlings suspected of infection were plated on water agar to confirm the presence of Phoma. In addition, approximately 20 seed-lings without lesions were plated to check for incipient infections but. no Phoma colonies were found.

Using both laboratory and greenhouse methods we have eval-uated over 100 seed lots from the United States, Canada, and several European countries. Rather than classifying sugarbeet seed lots solely on the percentage of seed units carrying P. betae, the results have led us to propose a system of classification which recognizes four basic infection types and appears to better describe the association of P. betae with sugarbeet seed.

V O L . 19, No. 1, M A R C H 1976 7

Type A . Little (<5%) or no Phoma present on the seeds as measured by laboratory and greenhouse trials.

Type B. Phoma present on a moderate percentage of the seeds (5-20%) but mostly superficial as shown by its easy removal with the NaOCl treatment. Causes little or no seedling disease in greenhouse plantings.

Type C. Moderate to high degree of contamination (30-60%) which is reduced but not eliminated by NaOCl treatment. Causes a moderate amount (20-40%) of seedling disease in soil trials.

Type D. Seeds heavily infected (>60%) with only slight reduction following NaOCl treatment. Causes fairly high amounts (>40%) of seedling disease.

Influence of Rainfall on Seed Infection Type The relation of climatic factors to contamination or infection of

sugarbeet seed by P. betae is illustrated by the results of laboratory and soil germination trials with seed lots from different climatic areas and with seed lots produced in the same area but in different years. Table 1 shows the results of analyses of seed lots produced in 3 areas of western North America.

Table 1. — Relation of precipitation to Phoma infection of sugarbeet seed — western North America.

Arizona 1970

Med ford, Oregon

1971 1972

British Columbia

1967 J 968 1972

8

3 3 4 0

12 4 2 8 1

3

3 t i .

2 2 2 6 2 1

2

0 0

2 0 5 3

6

13

3 6 4 0

54 121 1 0 9

0

2 3 18

I 6 8 3 8

0

< 1 1

1 3 1 16

-

1 4

5 3 7

9

A

B B

A

C - D B - C

a Pretreatment — 0.5% NaOCl for 5 min.

The Phoenix area of Arizona is almost rain-free during May and June when beet seed is maturing and being harvested. Laboratory tests with 4 seed lots produced in 1970 showed no Phoma on any of the seeds, so they were classified as type A seeds. Because of the mild winters only beet varieties of easy or moderate bolting tendencies can be repro-duced in the Phoenix area.

The Medford area of Oregon, where harder bolting varieties are produced, has considerable rainfall during the winter but very little

Seed

Grown

Precipitation (mm)

Days before harvest

31-60 1-30 H a n . Total

Phoma Infection (%) Inf. Water Agar Soil Type

Untr. NaOCl a Sell. Inf. (A-D)

8 JOURNAL OF THE A. S. S. B. T.

during July and August when beet seed is maturing and being har-vested. During 1971 and 1972 the seed lots tested showed about 20% Phoma contamination, which was probably associated with the early rainfall. Very little penetration of the seed units occurred, as shown by inoculum reduction following NaOCl disinfestation and by a very low-percentage of seedling infection. This seed was classified as having a grade B infection type.

In the Puget Sound area of British Columbia the results in 3 seasons were quite variable. In 1967 there was little rainfall before or during harvest and very little Phoma was found on the seed samples. In soil 5% of the seedlings showed Phoma infection, which was more than would be expected from the laboratory tests. In 1968 there were fairly heavy rains, especially late during the harvest period, and the seed lots showed high counts of Phoma on the seed and fairly high seedling infection. In 1972 most of the rain fell early during June and very little during the harvest period. The result was seed lots with a moderate amount of Phoma contamination on seed, which was much reduced by disinfestation treatments, and fairly low seedling infection. The British Columbia seed was classified as type A in 1967, C-D in 1968 and B-C in 1972.

Similar information was compiled for seed lots produced during 2 years in Italy, France, and Ireland, and is reported in Table 2.

Table 2. — Relation of precipitation to Phoma infection of sugarbeet seed — Europe.

Italy 1969 1970

France 1969 1970

Ireland 1968 1970

21 52

79 69

60 97

57 46 27 20

51 95

61 58

30 13

149 101

124 99

160 177

270 256

13 1 8 15 1 7

47 37

90

20 15

70 62

21 33

70 73

B B

C C

D D

aPrecipitation data provided by C. Comerford, Irish Sugar Company, Dublin, Ireland.

bPretreatment — 1 % NaOCl for 10 min. Laboratory tests by A. Mangan, Dublin, Ireland.

In the area of seed production along the Adriatic coast in Italy, light rainfall occurred during the 60 days preceding harvest and also during the harvest period in 1969 and 1970. The seed lots produced in each year carried a low percentage of Phoma contamination which was apparently superficial, since it was effectively removed by a NaOCl treatment. Less than 10% of the seedlings from nontreated seed in

Seed Grown

Precipitationa (mm) Days before harvest

31-60 1-30 I larv. Total

Phoma Infection (%) Water Agar Soil

Untr . NaOCl b Sell. Inf.

Inf. Type

(A-D)

VOL. 19, No. 1, MARCH 1976 9

pasteurized soil were infected by Phoma and the seed was classified as type B.

In the Mediterranean region of France, however, there was con-siderably more rainfall than in Italy, especially during the 60 days before harvest in both 1969 and 1970. The seed lots averaged 35 to 50% of the seed infected by Phoma, with only about half of the in-oculum removed by NaOCl treatment. Seedling infection averaged 20 to 30% and the seed was classified as type C.

In the Limerick area of Ireland there was frequent and moder-ately heavy rainfall during the 60 days before and quite heavy rainfall during the harvest periods in 1968 and 1970. The seed lots carried high percentages of Phoma, which penetrated deeply into the seed units and produced high percentages of seedling infection. In contrast to other European seed lots, those produced in Ireland in 1968 and 1970 were typical of infection type D.

A more detailed study was made of seed lots produced in the Willamette Valley of Oregon because most of the beet seed used in western United States comes from that area. Several seed lots were analyzed from each year's production from 1967 to 1973, with the seed from two years (1971 and 1973), part of which was harvested before and part after a heavy harvest rain, being reported separately.

The results in Table 3 show that in 1967 and 1970 there was very little rainfall during the 60 days before harvest or while the seed stalks were drying in the field. As a result the seed was free or nearly free of Phoma infection and classified as type A seed. However, in 1969, when rain fell during the period 31-60 days before harvest, and no later, the seed lots carried only superficial Phoma infection and seedling infection was very low, typical for seed infection type B.

In contrast, during 1968 a period of very heavy rain occurred during harvest while the seed stalks were in the swath and a high percentage of the seeds were apparently deeply infected by Phoma and resulted in high percentages of infected seedlings, indicating infection type D. An unusual situation occurred in both 1971 and 1973 in which a rain fell during the harvest period. A portion of several seed lots had been harvested before the rain and this permitted direct comparisons of the effect of the rain on subsamples of the same seed lots. Samples threshed prior to the rainy period showed moderate Phoma infection while those rained on while curing in the field showed higher infection levels.

The seed lots produced in 1972 showed a surprisingly high per-centage of Phoma infection in view of the very low rainfall 60 days before and during harvest. This may be accounted for by the fact that all Willamette Valley seed fields are irrigated by overhead sprinklers from late spring until approximately 30 days before the cutting of seed

10 JOURNAL OF THE A. S. S. B. T.

Table 3. — Relation of precipitation to Phoma infection of sugarbeet seed — Willamette Valley, Oregon.

1967

1968

1969

1970

1971c

1971d

1972

1973 r

1973d

18

3 8

7 5 c

2 2

7 8 c

7 8

18

3 5

3 5

0 tr.

10

1

1

3

3

3

t r .

t r .

106c

1

i r .

8

8 6 c

4

0

2 0

18

1 5 4

7 7

2 3

8 9

1 6 7

2 5

3 5

5 5

9 1

6 6

2 4

0

3 8

4 8

4 5

3 3

6 1

5 6

1

0

10

3 4

2 5

1

14

2

3 2

1

0

18

2 5

4

8

11

A

C - D

B

A

C

C D

B - C

B - C

C

a Harvest period extended from cutting of the seed stalks to threshing of the dried seed and ranged from 10 days to 30 days depending on the area and season. If the harvest period could not. be identified, rainfall for a 30-day period was reported. bPretrcatment — 0.5% NaOCl for 5 min. cEarly threshing before rainfall.

d Late threshing after heavy rainfall dur ing curing period. e Rainfall events which are felt to have been important in the ultimate seed infection grade.

stalks. In some years this may provide enough moisture to distribute Phoma spores and promote infection of immature seed units.

Effect of Seed Processing on Phoma Seedling Infection Seed lots carrying infection types A or B showed very few seeds

carrying Pkoma after disinfestation with NaOCl, indicating that most of the contamination was superficial. They also produced very few in-fected seedlings in greenhouse tests. Seed lots type C and D, however, carried high percentages of Phoma, with some penetration of the pathogen into seed tissues, and it was important to learn what effects seed processing, in which superficial tissues are milled away, could have on seedling infection.

Tests were run with processed and nonprocessed seed of the same lots to determine what effects processing has on the amount of in-oculum carried on seed and the efficiency of fungicidal seed treat-ments. The results reported in Table 4 show whole seed produced in an area with abundant summer rainfall and having 80-90% Phoma infection, and classified as infection type D, compared with a seed lot produced in an area with less summer rainfall and classified as infec-tion type C. Disinfestation of type D whole seed with NaOCl did not reduce the percentage of seed units showing Phoma on water agar, but

Year

Precipitation (mm) Days before harvest

31-60 1-30 Harv.a Total

Phoma Infection (%) Water Agar Soil

Untr . NaOCl b Sdl. Inf.

Inf. Type

. (A-D)

V O L . 19, N o . 1 , M A R C H 1976

Table 4. — Effect of processing and treating of type C and D sugarbeet seed on Phoma infection.

Laboratory Analysis Nondisinfested 84 90

Disinfesteda 90 88

Seedling infection Untreated 77 73 Trea t ed b 45 61

66 45

33 21

34 18

14 2

aSeed disinfested by immersion in 0.5% NaOCl for 5 niin. bSeed t rea tment consisted of Dcxon and PCNB applied to seed at rate of 87.5

g a.i./lOO Kg seed and 93.7 g a.i./lOO Kg seed, respectively.

with type C whole seed, the percentage was reduced one-half by disin-festation.

In greenhouse tests, the type D whole seed showed 77% infected seedlings with no fungicidal treatment, and 45% infected seedlings after seed t r ea tmen t with Dexon [p-(d imethylamino) ben-zenediazosodium sulfonate] at 87.5 g a.i. per 100 Kg seed (1.4 oz. a.i. per 100 lb.) + PCNB (pentachloronitrobenzene) at 93.7 g a.i. per 100 Kg seed (1.5 oz. a.i. per 100 lb.). This represents the combination treatment most commonly used in the western United States. In con-trast, the type C whole seed showed 34% infected seedlings without seed treatment and only 14% with the seed treatment listed above.

After the seeds of the two lots were commercially processed by milling to remove cortical tissues, water agar trials indicated that the type D seed showed the same level of seed infection as the nonproces-sed seed of that grade, but the processed type C seed showed only about 2/3 as much seed infection or carriage as the nonprocessed type C seed.

In greenhouse trials the processed type D seed showed as much seedling infection as the unprocessed seed with or without seed treat-ment. The untreated processed type C seed, however, showed only half as many seedling infections as whole seed. After treatment with Dexon + PCNB the seedling infection was reduced to a very low level. Similar results have been obtained with several other seed lots and it is quite clear that processing seed with type D infection does not improve the Phoma rating of the seed, nor incrase the protection provided by relatively mild seed treatments. This is undoubtedly due to the deep penetration of the tissues of the seed unit by the fungus and the impossibility of removing or exposing the inoculum by milling away the superficial tissues. On the other hand, the results with seed lots

Percent Phoma Type D seed Type C seed

Whole Processed Whole Processed

12 JOURNAL OF THE A. S. S. B. T.

carrying type C infection show that even though a high percentage of the seed units carry Phoma, most of the inoculum is in the superficial tissues where it can be reduced by a disinfestant and can be removed or exposed by processing so that fungistatic protectants can reduce seedl-ing infection to a very low level.

Seed Treatments For many years the standard control for Phoma seedling infection

in Europe was treatment of the seed with volatile ethyl or methyl mercury fungicides, which were applied as dusts or liquids directly onto the seeds. Similar seed treatment fungicides were also used in North America when Phoma-infected beet seeds were imported from Europe. However, because the seed lots produced in the moist climate of Ireland were heavily and deeply infected by Phoma betae, even these treatments provided only partial control. In 1 951, while on a Marshall Plan assignment in Ireland, the senior author demonstrated the very effective control of seed-borne Phoma by immersing, or steeping, the seed for 20 minutes in a 40 ppm solution of ethyl mercury phosphate (EMP) with a seed/solution ratio of 1:8 on a w/w basis (10). This treatment was first used commercially in Ireland in 1952 (5) and continued until 1972 when seed production was transferred largely to the drier Mediterranean area.

In 1954, Gates and Hull (7) also reported very good results with the EMP steep and since 1961 all sugarbeet seed in Great Britain has been steeped in ethyl mercury phosphate (4). In recent years, however, the use of ethyl and methyl mercury compounds as seed treatments has been discontinued in most northern European countries, and except for England, these countries have shifted their beet seed production to areas of lower summer rainfall such as Italy, France, Austria, Yugos-lavia, and Turkey. At present over 90% of the sugarbeet seed used in western Europe is genetic monogerm or mechanical monogerm all of which is processed by rubbing and much of which in some countries is also pelleted.

The fungicides which are presently most commonly used as seed treatments in Europe are methoxyethylmercury compounds, thiram, maneb or mancozeb. In North America the most commonly used seed treatment fungicides are Dexon alone or in combination with PCNB although maneb or captan are used in some areas. These fungicides are only partially effective with seed carrying the D type of Phoma infection or with unprocessed seed carrying the G type of infection but in our trials gave satisfactory control with processed seed carrying the B or C type. The effects of seed processing and seed treatment with Dexon and PCNB on the infection of sugarbeet seedlings from 4 seed lots carrying the C type of Phoma infection are presented in Table 5. In similar trials seed treatment with thiram, maneb, or TCMTB did not differ consistently or significantly from the Dexon-PCNB seed treatments.

V O L . 19, No. 1, M A R C H 1976 13

Table 5. — Effect of seed process ing and treating on Phoma infection of sugarbeet seedlings.3

Percent infection of seedlings

per seed lot3

Seed

Whole Processed Processed

Trea tment None None Dexon + PCNB

1

17.8a 4.2b 1.1b

2 3 41.1a 30.9b

1.8c

42.4a 19.5b

4.2c

4

24.1a 10.3b

3.5c

aAll seed lots carried the C type of Phoma infection. bColumn entries followed by the same letter do not differ significantly (P = 0.05)

by Duncan's Multiple Range test.

Summary and Conclusions It is well known that contamination or infection of sugarbeet seed

by P. betae is associated with rainfall during maturity and harvesting of the seed crop. Field observations, meterological records and laboratory analysis of seed samples suggest that rainy and cloudy periods dur-ing the 60 days preceding harvest favor the build-up of inoculum and its spread to seed stalks and flower parts. Irrigation with overhead sprinklers during this period may also contribute to the abundance of inoculum and to seed contamination or superficial infection. The deep penetration of seed units by P. betae appears to be associated with periods of rainfall while the cut seed stalks are curing in the field.

In the laboratory, culturing the seed units on water agar offers a convenient method of identifying the presence of P. betae on the seed. If part of each sample is plated without disinfestation and part after immersion in NaOCl solution, the results indicate whether the seed-borne fungus exists primarily as surface contamination, superficial infection or deep seated infection. The percentage of seedlings show-ing Phoma infection when grown in pasteurized soil is not only related to the total percentage of seed units carying Phoma, but also to the infection type as shown in laboratory tests. Therefore, we are suggest-ing with reference to seed-borne Phoma, that seed lots be classified as types A, B, C or D according to the percentage of seed carrying the fungus and also the type of infection as indicated by laboratory and soil tests.

Processing of sugarbeet seed by rubbing to remove cortical tissues strikingly reduced the percentage of Phoma-infected seedlings from B or C type of infection (Tables 4 and 5). With seed lots carrying D type of infection, however, processing did not reduce the incidence of seedling infection in soil tests.

Treating sugarbeet seed carrying D type Phoma infection with protective fungicides such as captan, Dexon, maneb, thiram, or TCMTB provides at best only partial protection against Phoma infec-

14 JOURNAL OF THE A. S. S. B. T.

t ion of seedl ings . With u n p r o c e s s e d seed lots ca r ry ing C type of infec-t ion, t r ea t ing the seed of ten p rov ides unsat isfactory pro tec t ion b u t with processed seed of the s ame lots, seed t r e a t m e n t s r e d u c e seedl ing infect ions to very low levels. A p p a r e n t l y p rocess ing of t he seed re-moves t he i nocu lum a long with superficial t issues or exposes the in-o c u l u m so tha t fungistatic chemicals effectively pro tec t t he g e r m i n a t -ing seedl ings .

T h e above in fo rmat ion indicates tha t t h e p r i m a r y requis i te for cont ro l of Phoma seedl ing infection is t h e avo idance of seed lots ca r ry-ing the D type of infect ion which a r e p r o d u c e d only in a reas with a b u n d a n t rainfall short ly be fo re o r d u r i n g the harves t p e r i o d .

In most years i t a p p e a r s that seed lots p r o d u c e d a long the Pacific Coast o f N o r t h Amer i ca o r in t h e M e d i t e r r a n e a n reg ion o f E u r o p e a r e unlikely to ca r ry deep - sea t ed Phoma infect ion, a l t h o u g h some lots may car ry fairly h igh pe rcen tages of con t amina t i on or superficial infect ion. After seed process ing a n d t r ea t i ng such lots wou ld be e x p e c t e d to p r o d u c e only a low inc idence of Phoma seed l ing infect ion. Howeve r , while these levels of infection may no t great ly inf luence t h e u l t imate s tands in suga rbee t p lant ings , recent, invest igat ions by Bugbee ( 1 , 2 , 3) indicate tha t s eed -bo rne Phoma betae may persis t in g rowing plants a n d initiate ser ious losses in suga rbee t s to rage piles as a resul t of Phoma r oo t rot . He also showed tha t the p a t h o g e n could survive in field soils or in s to rage a reas for a t least 26 m o n t h s . T h e s e conclus ions led h im to u r g e seed p rocessors to use fungicidal seed t r e a t m e n t s m o r e effective against P. betae. W h e t h e r t he levels of P. betae descr ibed h e r e a r e in fact unaccep tab le in those a reas w h e r e beets a r e s to red in piles is not known, bu t seed lots g r o w n in a reas of low s u m m e r rainfall would a p p e a r to pose little h a z a r d as sources of seedl ing disease following n o r m a l commerc i a l pract ices.

Literature Cited 1) BUGBEE, W. M. 1974. A selective medium for the enumeration and

isolation of Phoma betae from soil and seed. Phytopathology 64: 706-708.

2) BUGBEE, W. M. and O. C. SOJNE. 1974. Survival of Phoma betae in soil. Phytopathology 64: 1258-1260.

3) BUGBEE, W. M. 1975. Dispersal of Phoma betae in sugarbeet storage yards. Plant Disease Reporter 59: 396-397.

4) BYFORD, W. J. 1972. The incidence of sugarbeet seedling diseases and effects of seed treatment in England. Plant Pathol. 21: 16-19.

5) CADOGAN, J. P. 1952. Control of seedling disease in beet. Irish Beet Grower 6: 70-73.

6) DUNNING, R. A. 1972. Sugar beet pest and disease incidence and damage and pesticide usage. J. I.I.R.B. 6: 19-34.

7) GATES, L. F. and R. HULL. 1954. Experiments on bkick leg disease of sugar-beet seedlings. Ann. Appl. Biol. 41 : 541-561.

VOL. 19, No. 1, MARCH 1976 15

8) LEACH, L. D. 1940. Influence of the pathogen, environment, and host response of the efficacy of seed treatment with sugar beets and some vegetable crops. Phytopathology 30: 788. (Abstr.)

9) LEACH, L. D. 1944. Incidence of Phoma infection on sugar beet seed and the efficacy of seed treatments. Phytopathology 34: 935 (Abstr.)

10) LF.ACH, L. D. 1946. Seed-borne Phoma and its relation to the origin of sugar beet seed lots. Proc. Am. Soc. Sugar Beet Technol. 1946: 381-388.

1 1) MANCAN, A. 1971. A new method for detection of Pleospora bjoerlingii infection of sugar beet seed. Trans . Br. Mycol. Soc. 57: 169-172.

12) MANCAN, A. 1974. Detection of Pleospora bjoerlingii infection on sugar beet seed. Seed Sci. and Technol. 2: 343-348.

Feeding Preference and Reproduction of the Beet Leafhopper on Two Russian Thistle

Plant Species

A. C. MAGYAROSY and J. E. D U F F U S 1

Received for publication November 7, 1975

Introduction Curly top disease is one of the most destructive diseases of sugar-

beet. In the United States, it is transmitted only by the beet leafhopper, Circulifer tenellus. The extremely complicated life cycle (l)2 of this in-sect in California involves migrations in the fall from the cultivated area of the San Joaquin Valley to the major breeding ground areas in the foothills on the west side of the valley, where eggs are laid on various host plants (3). Large areas of open range, beet leafhopper breeding areas, are infested with species of Russian thistle.

In an effort to reduce curly top losses in California, each fall thousands of acres of Russian thistle are treated with insecticides by the State Department of Agriculture to control the vector.

It has become apparent in the last several years that the vegeta-tion in the beet leafhopper breeding areas is changing. Among such changes, the dominant species of Russian thistle, Salsola iberica (2), is being replaced by another Russian thistle species, S. paulsenii (2) (barb-wire thistle). The ecological basis for this replacement is not known but it is quite possible that these plant population changes will continue and will have an impact on the epidemiology of the beet leafhopper in the San Joaquin Valley and in the adjacent breeding areas.

The high operational cost of the spraying program and the pre-liminary observation by the State Department of Agriculture that S. paulsenii seems to be a poor host of the beet leafhopper prompted us to investigate some of the biological properties of the beet leafhopper on these hosts.

Materials and Methods Russian thistle (S. paulsenii and S. iberica) were grown in 9 cm pots

under normal greenhouse conditions. In all experiments, 7-8 week old plants were used. Healthy beet leafhoppers were reared on sugar-

1 Plant Pathologists, University of California and U.S. Department of Agriculture, ARS, P.O. Box 5098, Salinas, California 93901. The authors are grateful to Mr. Arnold L. Morrison for his technical assistance throughout this investigation. Supported by the Curly Top Virus Control Program.

2Numbers in parentheses refer to literature cited.

V O L . 19, N o . 1 , M A R C H 1976 1 7

beets at 30°C. Only the adults were used. To study the feeding or selection preference of the beet lcafhopper, we designed a box with glass sides and with four 9 cm holes in the bottom. Two plants of each thistle species, S. paulsenii and S. iberica, of the same size were randomly placed in the box through the bottom holes and then 100 healthy beet leafhoppers were added. The plants were isolated from each other at the base but the box was common to the plants at the top. The leafhoppers had a free choice to move on the plant species and were allowed to feed for 30 min. After this time period, they were anesthetized by administering CO2. Plants were removed from the box and insects were immediately counted. In preliminary tests, anesthe-tized insects frequently fell into the soil surrounding the plants and were lost; therefore the soil was covered with aluminum foil to reduce error. To determine the breeding characteristics of the beet leaf-hopper, plants of each Russian thistle species were placed in a standard leafhopper cage with 50 healthy female beet leafhoppers at 30°C. After ten days, the beet leafhoppers were removed. After 30 days, the nymphs were counted on the test plants. Leafhoppers placed on sugarbeet plants served as controls.

Results and Discussion Results of our investigations show that S. iberica is the preferred

feeding host of the beet leafhopper (Table 1). On the contrary, no differences were found regarding the reproduction of the beet leaf-hopper on these two Russian thistle species (Table 2).

Table 1. — Preference of beet leafhoppers on two plant species, Salsola paulsenii and S. iberica.

Plant Species No. of leafhoppers recovered

Salsola paulsenii 13 Salsola iberica 58.7

In one exper iment , 100 leafhoppers were randomly allowed to feed on two of each plant species in a specially designed insect-proof cage. After 30 min., leafhoppers were anesthetized by CO2 and counted. Values are significant at the 1.0% level and represent the average of 10 exper iments .

Table 2. — Breeding characteristics of beet leafhoppers on two Russian thistle plant species.

Plant species No. of beet leafhoppers hatched3

Salsola paulsenii 35 Salsola iberica 40 Control (Beta vulgaris) 90

aFifty female beet leafhoppers were placed on three different plant species. After 10 days, they were removed and 30 days after, the newly hatched nymphs were counted. Values represent the mean of 9 exper iments .

18 JOURNAL OF THE A. S. S. B. T.

In light of o u r da ta , the ques t ions arises, wha t species of Russian thistle shou ld be sp rayed a n d when in o r d e r to obta in an effective cont ro l of t he beet l ea fhoppe r .

Russian thistle p lan t popu la t ions occur mainly in mixed s t rands ; however , large acreages covered by the barb-wire type of thistle can be de tec ted by aer ia l m a p p i n g . On t h e basis of t h e low n u m b e r s of beet l ea fhoppers f o u n d on this species a n d o u r f ind ings that this Russian thistle species is no t t h e p r e f e r r e d feed ing host of beet leaf-h o p p e r s , t he sp ray ing of these p l an t popu la t ions in t h e fall is p robab ly no t just if ied. In a reas w h e r e the d o m i n a n t p lan t species is S. iberica a n d w h e r e large n u m b e r s o f beet l ea fhoppers a r e found , sp ray ing should be r e c o m m e n d e d .

T h e ep idemio logy o f t he bee t l e a f h o p p e r p e r t a i n i n g to these two Russian thistle p lan t species is f u r t he r compl ica ted by the fact that ne i t he r of these species is a good host for the cur ly t op a g e n t in n a t u r e (Magyarosy a n d Duffus, u n p u b l i s h e d ) .

S u m m a r y

The host p lan t selection a n d r e p r o d u c t i o n of the beet l e a f h o p p e r (Circulifer tenellus), vector of t he curly t o p agen t , was invest igated on two epiderniologically i m p o r t a n t Russian thistle species. Salsola iberica (tumblevveed) i s t he p r e f e r r e d feed ing host of the bee t l ea fhoppe r . No di f ference was de t ec t ed be tween 5. iberica ( tumbleweed) a n d S. paul-senii (barb-wire thistle) as far as the r e p r o d u c t i o n of t he beet leaf­h o p p e r is c o n c e r n e d .

Literature Cited

(1) BENNETT, C. W. 1971. T h e curly top disease of sugarbeet and other plants. The American Phvtopathological Society, Monograph No. 7. p. 43-62.

(2) BEATLF.V, J. O 1973. Russian-thistle (Salsola) species in the western United States. J. Range Mang. 26:225-226.

(3) SEVERIN, M. M. P. 1930. Life history of beet leafhopper, Eutellix tenel­lus (Baker), in California. Calif. Univ. Pub. Entomol. 5:37-38.

Sugarbeet Storage Rot in the Red River Valley, 1974-75

W. M. BUGBEE and D. F. C O L E 1

Received for publication November 5, 1975

Each season rot of sugarbeets in storage accounts for losses of sugar. Estimates of the amount of this loss have not been based on sample data. Our objectives were to sample and examine roots as they began the factory process, to determine the amount of rotted tissue, identify the causal pathogens and, on the basis of the data, to estimate losses in the Red River Valley.

Materials and Methods The survey was made from November 6, 1974, through March 12,

1975, at the American Crystal Sugar Company factory, Moorhead, MN. Samples were removed from the picking table on alternate days. Two samples were taken at randomly selected 12-h intervals on each sample day. Sample size was a standard tare bag of 10-17 kg (22-37 lbs). Samples from 6 factories in the Red River Valley were compared on January 24, 1975. During a 10-minute period four samples were ob-tained at the picking table of each factory.

The roots were returned to the laboratory, weighed, quartered longitudinally, divided into topping classes, and the decayed portions removed and weighed. Frozen tissue also was removed and weighed. The roots were classified into those with no crown tissue removed, all crown tissue removed, or partial crown removed. Rotted or frozen tissue was expressed as percent by weight. The tons of rotted tissue that were processed daily was determined by multiplying the percent rot derived from the sample times the tons of production for that particu-lar day. This same sample percent also was used for estimating rot on the following day when no sample was taken.

Rotted tissues from the crown, pith, body, and tail of the root were examined for pathogens. Rotted tissue samples of uniform size were removed with a cork borer and eight slices from each portion of the root were plated on potato-dextrose agar.

Results When this survey began on November 6, 1974, 10 tons of rotted

sugarbeet tissue was being processed daily at Moorhead. The daily 1Research Plant Pathologist and Research Plant Physiologist, Agricultural Research Service, U.S.

Department of Agriculture. Cooperative investigations of the Agricultural Research Service and the North Dakota Agricultural Experiment Station, Fargo, ND 58102. Approved by the Director of the Agricultural Experiment Station as Journal Series Article 648.

2Numbers in parentheses refer to literature cited.

20 JOURNAL OF THE A. S. S. B. T.

Figure 1. — Running average of the estimated daily amount of rotted sugarbeet tissue entering the Moorhead factory.

A 1 -day comparison among the six factories showed the amount of rot ranged from 0.5 to 2.1% by weight with no statistical difference (Table 1).

Phoma betae (Oud.) Frank and Penicillium claviforme Bainier were the most prevalent pathogens. P. betae was more abundant than P. claviforme in pith tissue, but the prevalence of both fungi was compara-ble in other rotted tissues. Incidence of Fusarium spp. was much lower than of Phoma or Penicillium. Botrytis cinera Pers. was least frequent and was restricted to pith, crown and body tissue (Table 2).

tonnage of rotted root tissue that was sliced gradually increased to nearly 100 tons at the end of the campaign (Fig. 1). The amount of rotted sugarbeet tissue that entered the factory during the 128-day survey period was 1.22% of the total tons that were processed. Of this amount, 0.18% was body, 0.10% tail, 0.36% crown, and 0.58% pith tissue. During the early part of the survey much of the rot tended to be associated with wounds on the tap root. The amount of rot remained low in the tap root and tail portions, but increased in the crown and pith as the season progressed (Fig. 2). Rot was 1.5 times as great in pith as in crown tissue.

VOL. 19, No. 1, MARCH 1976 21

Figure 2. — Running average of the daily amount of rot occurring in the crown, pith, tap root, and tail of tap root at the Moorhead factory.

22 JOURNAL OF THE A. S. S. B. T.

Table I. — Topping classification, frozen tissue, and decay in beets selected from the picking tables of six factories on January 24, 1975.

Crowns removed (% of roots) Percent by weight Factory

Hillsboro Drayton East Grand Forks Crooks ton Wahpeton Moorhead

Mean LSI) 0.01

None

7c l l a

16 13 14 10 19 14 n s

Partial

% 8 3 8 2 7 9 7 8 8 6 7 5 8 0 n s

A l l

% 6 2 7 8 5 6 6

n s

Frozen

% 5 5 51

8 5 8 8 6 12 4 5 2 8

Decay

% 2 . 0 0 .7 1.2 0 .5 2.1 1.5 1.2 n s

aAverage of four 1-bag (10-17 kg) samples.

The frequency of roots with different amounts of crown tissue removed did not differ during the sampling period. Of the 2,246 roots examined from Moorhead, 23% had no crown removed, 6% had all the crown removed, and 71% had part of the crown removed. Data from individual factories were similar (Table 1).

The average amount of frozen tissue processed was 34% for the entire sample period but, on a daily basis, approached 75% at the end of the campaign.

Discussion To our knowledge, this is the first estimate in the United States of

losses of sugarbeets from decay that has been based on experimental data. From these loss data, we have estimated the loss of sugar caused by the decay of sugarbeets. During the 128-day survey period, 456,820 tons of sugarbeets were processed at the Moorhead factory. This tonnage times 1.22% equals 5,583 tons of rot, having a potential sugar yield of 1,113,240 lb. Much of the invert sugar in this rotted tissue probably was metabolized by microorganisms to non-melassigenic con-stituents. The melassigenic factor for the Moorhead factory after this campaign was 1.6. Undoubtedly, rotted tissue has a melassigenic factor higher than 1.6. A conservative estimate then would be that an addi-tional 1,781,184 lb (1,113,240 x 1.6) of sucrose went to molasses

Table 2. — Prevalence of four storage rot pathogens in stored sugarbeets deter-mined by plating rotted tissue of roots entering a Moorhead factory from 2 December 1974 through 12 March 1975.

Phoma betae Penicilliurn claviforme Fusarium spp. Botrytis cinerea

Pith

32 21

4 0.4

Percent of

Crown

23 18

8 0.9

plated tissue

Body

12 14

8 1

Tail

10 18 11 0

Total pieces plated: 2,656.

VOL. 19, No. 1, MARCH 1976 23

because of the melassigenic properties of the rotted tissue. Therefore, the total sugar loss was estimated at 2,894,424 lb. Sugar losses probably were comparable at the other five factories in our region. The total sugar loss for the Red River Valley then could be estimated at 17,366,544 lb. At 20-45 cents per pound the loss would represent $3,473,308 to $7,814,945 minus a return from the molasses sold. This loss also could be expressed as 0.0495 lb of sugar lost/ton/day, or 10% of the 0.5/lb/ton/day loss which is considered average for our region.

These results support earlier observations that P. betae is the most important pathogen that causes decay of sugarbeets in the Red River Valley. The newly recognized pathogen P. claviforme (2)2 was nearly as prevalent as P. betae but does not decay root tissue as rapidly as P. betae. The low incidence of B. cinerea probably was due to the antagonistic

ability of P. claviforme (Bugbee, unpublished data). Partially crowned roots decay faster than uncrowned or com-

pletely crowned roots because the exposed pith tissue is very suscepti-ble to attach by P. betae (1). This survey has shown that 71 % of the roots examined were partially crowned and that rot in the crown and pith was 2-6 times as great as in the tail or body. This suggests sugar loss from decay might be reduced if roots were uncrowned.

A Russian report more than 35 years ago referred to the suscepti-bility of the central core of the crown and suggested that crowns be cut cone-shaped rather than straight across to reduce losses from storage rot (3).

Summary Sugarbeet roots were sampled from the picking table at a

Moorhead, MN, factory from November 6, 1974, through March 12, 1975. During this 128-day period 1.22% by weight of roots processed were rotted. This amounted to an actual sugar loss of 1,113,240 lb plus another loss estimated at 1,781,184 lb of sucrose going to molasses (1.6 melassigenic factor). About 71% of the roots were partially crowned. This practice probably contributed to rot development. A sampling of roots from the Red River Valley showed that the amounts of crown removed and decay were similar among six factories. Three fungal pathogens were involved: Phoma betae, Penicillium claviforme, and Botrytis cinerea. The prevalence of P. betae was slightly greater than of P. claviforme. Both were much more prevalent than B. cinerea.

There was slightly more rot, associated with wounds, on the tap root than on the crown early in the storage period. Rot in the crown region developed slowly but eventually accounted for the greatest portion of rotted tissue compared to the tap root or tip of the tap root.

24 JOURNAL OF THE A. S. S. B. T.

Literature Cited (1) BUGBEE, VV. M. 1975. Peroxidase, polyphenoloxidase , and en-

dopolygalacturonate transcliminase activity in different tissues of sugarbeet infected with Phoma betae. Can. J. Hot. 53:1347-1352.

(2) BUGBEE, VV. M. Penicillium clavifoniie and Penicillium variabile: storage rot pathogens of sugar beets. Phyropathology 65:926-927.

(3) PANASIUK, M. P. (ed.). 1938. Sugar beet diseases and means of their control. (Transl. from Russian). Sveklovodstvo 3:203-392.

Breeding Sugarbeet for Resistance to Yellow Wilt1

J O H N O. GASKILL 2 and R O B E R T O EHRENFELD K.3

Received for publication November 12, 1975

Introduction Yellow wilt, potentially an extremely destructive disease of sugar-

beet, is reliably considered the principal cause of the collapse of the beet sugar industry in Argentina more than 30 years ago (2, 3, 4).4

In Chile, the disease was first recognized in experimental sugarbeet plantings in 1945 and has been present in the commercial sugarbeet crop since the beginning of the beet sugar industry in that country about 9 years later (1). That industry currently is coping with the dis­ease by avoiding areas where incidence of the vector (Paratanus exitiosus Beamer) is especially high and by the use of certain modern insecti­cides (1). Effectiveness of the latter is dependent upon accurate entomological surveillance and precise timing of insecticide applica­tions with respect to vector migrations. Consequently, control costs are substantial and effectiveness is variable (8).

Yellow wilt also is an important problem in the production of sugarbeet seed in Chile. Arentsen et al. (1) reported that the severity of the disease resulted in the shifting of the sugarbeet-seed industry southward, first from the province of Coquimbo (north of Santiago) to the province of Aconcagua, during the 1950's, and later to the zone between Santiago and Curico. The use of insecticides for control of the vector is now a standard practice in all sugarbeet seed fields in Chile.

Although yellow wilt has been found only in Chile and Argentina, it must be considered a very serious threat to the sugarbeet crop in many parts of the world, including much of the western United States. To illustrate this point, it is pertinent to point out the following: (a) The only known vector is a leafhopper that thrives on many weed species common throughout the semiarid regions of the world where the sugarbeet is adapted, including the western United States; (b) most

1 Joint contribution by the Agricultural Research Service. U.S. Department of Agriculture, and the Beet Sugar Development Foundation [Cooperative Agreements 12-14-100-9334(34) and 12-14-100-10,624(34)] in cooperation with the Industria Azucarera Nacional S.A. and the Colorado State University Experiment Station.

2 Collaborator, Agricultural Research Service, U.S. Department of Agriculture, arid Project Consultant, Beet Sugar Development Foundation, Fort Collins. Colorado.

3Ingeniero Agronomo, Industria Azucarera Nacional S.A., Casilla 6099, Correo 22, Santiago, Chile.

4Single-digit numbers in parentheses, occurring in the text, refer to literature cited.

26 JOURNAL OF THE A. S. S. B. T.

of the best host species of the vector also are hosts of the recognized causal agent of yellow wilt; and (c) climatic conditions where the vet tor thrives in Chile and Argentina are similar to those in many other semi-arid regions suitable for sugarbeet production, including much of the western United States (3, 4, 5). Apparently, the vector occurs only in Chile and Argentina at present. However, with modern methods of transportation, its spread to other regions seems inevitable.

The chief purpose of this article is to describe the progress made in breeding sugarbeet for resistance to yellow wilt. However, since important etiological, host-range, and other information has been accumulated since the drafting of the comprehensive 1967 report by Bennett et al. (3), this article has been expanded to include some of the new information. For further details in this category, the reader is referred to "Literature Cited," particularly (1), (4), and (9).

Host Range of the Disease A list of plant hosts of yellow wilt was included in the article by

Bennett et al. (3). A list of host species, expanded to include more recent observations (1,4, 5), is presented in Table 1. Of the 12 families represented by the 43 species listed, the Chenopodiaceae, Cruciferae, and Geraniaceae probably are the most important as sources of yellow wilt inoculum for the sugarbeet crop in Chile.

Host Range of the Vector The only known vector of yellow wilt, Paratanus exitiosus Beamer,

belongs to the same subfamily of insects as the beet leafhopper (Cir-culifer tenellus Baker), the vector of North American sugarbeet curly top, and the wide host range of the two species is about the same (3, 4). The following statement by Bennett (4) is particularly significant: " . . . nearly all of the best host plants for P. exitiosus are also hosts of the causal agent of the yellow wilt disease."

Causal Agent or Agents of the Disease For many years yellow wilt was believed to be caused by a virus

(2, 3). Before 1967, no mycoplasma-like organism (MLO) was known to be the causal agent of any plant disease. The possibility that yellow wilt is caused by an MLO was suspected when it was observed that temporary remission of symptoms occurred following treatment of infected sugarbeet plants with certain antibiotics (1, 4, 7). Strong con­firming evidence subsequently was obtained by Urbina-Vidal and Hirumi at the Boyce Thompson Institute for Plant Research, Yonkers, N.Y., in 1973 (9). Flection micrographs consistently showed abundant bodies of MLO type in tissue specimens from yellow-wilt-infected sugarbeet plants and no such bodies in specimens from apparently healthy plants. However, the results of this study also suggested the

V O L . 19, N o . 1 , M A R C H 1976

Table 1. — Plant hosts of yellow wilt.

Family Species Remarks Aizoaceae Tetragonia tetragonioides

(Pall.) Klze. Amaranthaceae Amaranthus retrofiexus

L.*# Caryophyllaceae Stellaria media (L.)

Cyrillo*# Chenopodiaceae Beta macrocarpa Guss.

Beta maritima L. Beta patellaris Moq. Beta vulgaris L. Beta vulgaris L. var. cicla L. Chenupodium album I...*# Chenopodium capitatum (L.) Aschers.# Chenopodium murale L.*# Spinaeia oleracea L.

New Zealand Spinach

Red-root amaranth ; pigweed

Chickweed; common in shady places

Sugarbeet, table beet, fodder beet Swiss chard

Lambsquar ters Strawberry blite

Nettle-leaf goosefoot Spinach. Highly susceptible to yellow wilt and may show symptoms in 9 days after infection. An excellent host of

Compositae Clichoriutn intybus L.*# Picris echioides L.*#

Sonchus sp.* Taraxacum officinale Web.*#

Convolvulaceae Convolvulus arvensis L.*#

Brassira sp.*# Capsella bursa-pastoris (L.) Medic.*# Diplotaxis mural is (L.)

nc.*# Lepidium bipinnatifidium Desv.* Rapistrum rugosum (L.) All.* Sisymbrium officin ale (L.) Scop.*# Erodium botrys (Cav.) Bertol.*# Erodium cirutarium (L.) L 'Her .*# Erodium moschatum (L.) L 'Her .*#

Geraniaceae

Ox- tongue . Shows marked symptoms when infected, but diseased plants may have symptomless shoots.

Bindweed. Shows marked symptoms of yellow wilt when infected, but apparent ­ly is very resistant to infection.

Shepherd 's purse

A very good host of P. exitiosus

Highly suscep t ib le to infect ion a n d injury

Yuyo

Hedge mustard

An excellent host of P. exitiosus Red-s tem f i la ree . An exce l len t host of P. exitiosus White-stem filaree. An excellent host of P. exitiosus

= Common weed in Chile = Common weed in the United States

28 JOURNAL OF THE A. S. S. B. T.

Family

Plantaginaceac

Polygonaceae

Port u lacaceae

Solanaceae

Species

Plantago insularis Eastw.# Plant ago lanceolata L.*# Plantago major L.*#

Plantago xnrginica L.*# Polygonum lapathifolium L.*# Rumex crispus L.*# Rumex spp. Calandrinia compressa Schrad. ex D C * Claytonia perjoliata Donn. ex Willd.# Portulaca oleracea L.*# Datura stramonium L.*# Hyoscyamus niger L. Lycopersicon escuientum Mill.

Nicotia na bigelovii (Torr.) S. Wats.# Nicotia na clevelandii Gray Nicotian a quadrivah •us Pursh

Remarks

C o m m o n plantain . Excellent host of P. exitiosus

Dock Dock: at least two species

Miner's lettuce

Purslane Jimson weed Black henbane T o m a t o . Apparen t ly not highly sus-ceptible to infection, but severely in-jured if infected. Indian tobacco

possibility that in add i t ion to MIX), a virus is involved in the yellow wilt disease. It is conceivable that the p r e s u m p t i v e virus, observed in yellow-wilt-infected mater ia l , plays a c o m p l e m e n t a r y role , a negat ive role, or no role a t all, in the express ion of s y m p t o m s . F u r t h e r eluci-da t ion of this m a t t e r is u rgen t ly n e e d e d .

Breeding for Res is tance

Materials, Methods, and Background Information

M o r e t h a n 381 s u g a r b e e t b r e e d i n g lines a n d var ie t ies w e r e eva lua ted u n d e r yellow wilt cond i t ions in A r g e n t i n a (1938-40) a n d Chile (1965-69) , bu t n o n e exhib i ted apprec iab le res is tance (4). O t h e r forms of Beta vulgaris L. (e.g., Swiss c h a r d , table beet , a n d f o d d e r beet) we re f o u n d to be qu i t e suscept ible , as w e r e B. macrocarpa Guss . a n d B. patellaris Moq. (3 , 4).

In t he early selection a n d b r e e d i n g work in A r g e n t i n a a n d Chile , sugarbee t plants wi thou t s y m p t o m s of t he disease w e r e selected u n d e r severe yellow wilt cond i t ions . T h e p rogen i e s were abou t as suscept ible

* = Common weed in Chile # = Common weed in the United States

VOL. 19, No. 1, MARCH 1976 2 9

as the parental varieties, and it was concluded that the selected plants were merely escapees (2, 3, 4).

Subsequently, in Chile, emphasis was placed on the selection of plants with symptoms of the disease but with some evidence of resis­tance — i.e., apparent ability to grow in spite of infection. When selec­ted plants with definite yellow wilt symptoms in the fall were removed from the held at that time, given appropriate artificial thermal induc­tion, and transplanted in the spring, all died without producing seed (4). The outcome was the same when such selected plants were transplanted in the fall and allowed to remain in the field throughout the winter and spring (4). When such plants, chosen in the fall, were allowed to remain in the field without transplanting, nearly all died without producing seed. In some large groups of such material, rare individuals produced very small amounts of seed (4).

Although the selection of infected but. apparently resistant plants has been emphasized in Chile since the early selection work referred to above, other methods have not been excluded. In fact, one of the most promising categories of material, RS-2b, is a product of repro­duction by 5 female plants, none of which developed symptoms during the season of vegetative growth or during the following winter and early spring.

It has been long recognized that some important conventional techniques apparently could not be used in breeding sugarbeet for yellow wilt resistance without a means of obtaining reasonably satis­factory seed production by selected (infected) plants after trans­planting. Based on earlier evidence that certain antibiotics can tem­porarily suppress symptoms (1, 4, 7), attempts were made in 1972 and 1973 to promote the production of seed by selected (infected) plants by means of repeated antibiotic applications throughout the winter and spring (8). The results in 1972 were inconclusive with respect to transplanted plants but were quite encouraging where treated plants were left undisturbed in the field evaluation and selection plots at the Estacion Experimental La Platina, near Santiago, Chile. In 1973, antibiotic treatments were limited to plants that were transferred from La Platina to isolated locations for seed production. These groups in­cluded both infected and apparently noninfected plants. With re­finements in techniques and with the aid of favorable weather, the results were relatively satisfactory. The procedure used may be out­lined as follows:

1. The selection and digging of plants in the 1972-73 field plots at La Platina were postponed until September, 1 973 (i.e., about the end of the winter season).

2. Promptly after selected plants were dug, the foliage was re­moved and the roots were immersed for 24 hours in a solution of Terramycin in tap water (250 ppm) and then transplanted

30 JOURNAL OF THE A. S. S. B. T.

in isolated groups in the Noviciado area, about 37 miles north­west of Santiago.

3. Terramycin solution (same as above) was sprayed on the foliage twice each week for about 2 months.

Various sugarbeet cultivars from the United States and Europe have been used as source material for yellow-will-resistance selection and breeding. Since curly top exists in Argentina and thus is con­sidered an important potential threat to the Chilean beet sugar indus­try, curly-top-resistant cultivars from the United States have been used more extensively than others as source material. After several years of selection, reproduction, and preliminary evaluation work, Arentsen et al. (1) and Bennett (5) described the following lines which had shown some evidence of resistance: RS-1, RS-la, and RS-lb, de­rived from the USD A line, C663, or US 75; RS-2, derived from US 75; and RS-3, derived from C663. The sources pertain to the initial female parents. The pollen source in each case is unknown.

The derivation of a particularly promising category of material may be described as follows.5 Plots planted at La Platina on October 1 5, 1969, included populations of the respective immediate parents of RS-la, RS-lb, RS-2, and RS-3. After all bolters and other undesirable plants were removed from those lines, 442 individuals remained in the field on June 20, 1970, to overwinter and to produce seed if possi­ble. Of these, 369 showed yellow wilt symptoms and 73 appeared healthy at that time. None of the former produced seed. Most of the remainder developed yellow wilt symptoms during the winter or spring and died prematurely. Actually, only five produced seed. Those five were in the population designated as the immediate parent of RS-lb. Yellow wilt symptoms appeared in four of them by about De­cember 4, 1970, and the fifth plant apparently remained healthy. The seed was harvested on January 2, 1971. That portion obtained from the apparently healthy plant was designated RS-2b(A), that obtained from the four diseased plants was labeled RS-2b(B), and a pool of a part of each of those lots was designated RS-2b. Increases of RS-2b(A) and RS-2b(B) were made promptly at Linares by the field overwintering method. RS-2b was included in the 1971-72 field plots at La Platina, together with RS-la, RS-lb, RS-2, and RS-3, for eval­uation and further selection.

The evaluation and selection programs at La Platina, reported herein, were conducted under conditions of natural disease exposure. The use of an individual-plant rating system, representing severity of yellow wilt attack, was initiated in the 1971-72 experiments. The use of replicated field plots with statistical analyses of the results was begun in 1973-74.

5Records of Rober to Ehrenfe ld K.

V O L . 19, N o . i , M A R C H 1 9 7 6 31

Evaluation Tests The results obtained in the experiments of 1970-71, as reported

by Bennett (5), suggested that some progress had been made in breed­ing for resistance. The results of 1971-72 and 1972-73 strengthened that tentative conclusion. The outcome of the 1973-74 experiments apparently left no doubt that measurable progress had been made and also indicated that further progress should be possible. A detailed presentation of results of all of these experiments in this report would not be worthwhile. Instead, detailed results are presented for relevant parts of the 1972-73 program and for all but minor portions of the 1973-74 group of experiments.

Experiments of 1972-73. The field experiments at La Platina in the 1972-73 crop season included a date-of-planting study. The sum­marized results (Table 2) indicated that the severity of yellow wilt attack was consistently and substantially lower in RS-2b(B) than in the com­mercial check variety, KWS-E. RS-2b(A) was intermediate in severity of attack. Since yellowing and necrosis caused by yellow wilt cannot be shown satisfactorily in black and white photographs, comparisons of KWS-E and RS-2b(B) were presented in color in reports covering the

Table 2. — Comparison of three sugarbeet lines in a date-of-planting study, La Platina, 1972-73.

Line1

RS-2b(A) KWS-K RS-2b(B)

RS-2b(A) KWS-K RS-2b(B)

RS-2b(A) KWS-E RS-2b(B)

RS-2b(A) KWS-E RS-2b(B)

rogued

(%)2

Planted Oct 85.9

0 . 0 •58.9

Planted Nov 84.4

0 . 0 36.7

Total no. 10,

1 2 5 3 2 6 2 3 1

15, 1 8 8 3 8 7 2 7 7

Planted Dec. 18, 52.7

0 . 0 17.8

5 1 2 4 0 4 3 7 6

0

1972; 17.6 17.5 53.7

Disease

_ grade

2

and %

3 disease ratings made Aug. .

6 .4

11.3 8.2

1972; disease rat, 20.7

9 . 8 10.6

6 .5 37.5 12.6

1972; disease ratings 44.5 25.5 61.4

27.6 17.6 50.9

13.7 10.6 14.1

Averages 10.2

9 . 5 1 1.6

13.6 8.0 6.1

26.4 12.3

7 .8

ings made Aug. 15.4

3 .9 25.0 20.4

9.7 15.2 made Aug.

10.7 4 . 5 4 . 0

13.2 5 .5 6 . 6

13.7 13.9

5 .9

21.7 15.5

9 . 6

total no.4

4

20, 1973 22.4 42.6 18.2

21, 1973 22.3 55.0 22.7

22, 1973' 16.8 44.6 14.6

20.5 47.4 18.5

5

13.6 8.3 6 .1

5 . 9 4 . 4 2 .2

0 . 6 1.0 0 . 0

6 . 7 4 . 6 2 . 8

Disease index 1

2.70 2.76 1.47

2.35 3.18 1.79

1.46 2.44 0.98

2.17 2.79 1.41

1Each line occurred in one plot (21 rows x 8.5 m) in each planting-date block. The 9 plots in this exper iment were a r ranged, from east to west, in the o rder shown. 2At convenient intervals dur ing the period, Dec. 13, 1972, to Julv 20, 1973, inclusive, all bolters were rogued throughout the entire exper iment . 3All plants remaining in representative rows of each plot after roguing of bolters. 4Basis of grades: 0 = without yellow wilt symptoms; 5 = dead. T h e disease index is a weighted average based on the number of plants in each grade.

32 JOURNAL OF THE A. S. S. B. T.

1972-73 experiments (8). As these photographs show, the degrees of both yellowing and leaf necrosis, especially the latter, were distinctly lower in RS-2b(B) than in KWS-E. These observations agreed with the numerical comparisons of the same lines (Table 2), although nearly 4 months elapsed from the time the photographs were made to the time the data were recorded.

Another highlight of the 1972-73 results at La Platina was the performance of one of the three introductions of B. maritima L. in a separate experiment. That particular introduction had been collected in its wild state several years earlier, near Wembury Bay, England, by Mr. Dewey Stewart, formerly Leader, Sugarbeet Investigations, in the Agricultural Research Service, LJSDA, now a Collaborator. Disease indexes for three consecutive plots in the experiment were as follows on August 27, 1973: KWS-E, 2.96; table beet, 2.72; and B. maritima (Wembury Bay) 1.06. The appearance of the latter is compared with that of the table beet, 4 months earlier, in Figure 2. These results suggest that superior genes for yellow wilt resistance exist in the Wembury Bay introduction of B. maritima and in other biotypes of that species.

Figure 1. — Yellow wilt injury in sugarbeet, typical of that occurring in commercial sugarbeet varieties in Chile in areas where incidence of the vector is high. The picture shows the variety, KWS-E, at La Platina, near Santiago, on April 14, 1972. (BSDF photo 72-J-19).

VOL. 19, No. 1, MARCFI 1976 33

Figure 2. — Comparison of table beet (row at right) with B. tnaritima from Wembury Bay, England; La Platina, April 27, 1973; planted October 10, 1972. (BSDF photo BW73-1-9).

Experiments of 1973-74. The held experiments at La Platina in the 1973-74 crop season consisted principally of evaluation tests of individual-plant progenies resulting from reproduction of selected plants of several RS lines under conditions of open pollination in 1972 — seed harvested in January, 1973. The 1973-74 plots were planted on November 22, 1973, and thinned and cared for in the usual manner. Bolters were rogued at convenient intervals during the 1973-74 crop season and the following winter. The numbers of such plants were not systematically recorded, and they have been disregarded in this report. As in the preceding year, yellow wilt developed later than usual; consequently, the recording of results was postponed until winter (actually July and August), 1974. This undertaking involved the rating of 1 7,715 plants individually for severity of yellow wilt attack.

One experiment (no. 4), a test of a few very small seed lots in 2-row plots with two replications, was considered unreliable and the results are not reported herein. Experiment no. 5, with plots 4 rows x 5m in size and with two replications, included six KWS lines or varieties with C663 and RS-2b(B) as checks. The average disease indexes for C663 and RS-2b(B) were 2.78 and 1.99, respectively. The averages

34 JOURNAL OF THE A. S. S. B. T.

for the six respective KWS entries ranged from 2.68 to 2.97. The dif­ferences among the seven entries having no background of selection for yellow wilt resistance (i.e. C663 and the KWS material) were con­sidered negligible.

All plots in experiments 1, 2, and 3 were 4 rows X 5m. The mater­ial evaluated in those experiments is listed in Tables 3, 4, and 5, respec­tively, together with the summarized results and the outcome of analyses of variance. The seed numbers for individual-plant progenies, listed in those tables, may be described as follows. Each number consists of four positions, separated by dashes, which indicate, from left to right: (a) the calendar years in which the parental seed was planted and its progeny harvested, respectively; (b) the location or area where

Table 3. — Comparison of sugarbeet lines for yellow wilt resistance; experiment 1, La Platina, 1973-74; 4 replications; results recorded July 16-19, 1974.

Entry n o .

1 2 3 4

5 6 7 8

9 10 1 1 12

13 14 15 16

17 18 19 2 0

Genera l F LSD (.0:

Seed no. or variety

71/3-1-3-L15 -L20

7 1/3-1-6-LSI -1.16 -L17 -LI 3

71/3-1-5-L3 7I/3-1-1-L3

71/3-1-5-L4 71/3-1-3-1.9

-1.27 -1.14

-L10 71/3-42-3-L2 71/3-1-3-L24

-L25

71/3-1-6-L15 71/3-1-1-L6 KWS-E

RS-2b(B)

mean

>) for comparison LSD (.01) for comparison

Description ~ 0

0 - E 0 -E 0

0 0-E I 0

0-E 1 0 0

1 0 0 0

0 - E 0 -E Comm. ck. Ycl. res.

of 4-of 4

wilt ck.

-plot averages -plot averages

No. of plants Per

Actual 77.0

101.3 98.8 59.3 72.0 52.3

104.8 76.0

101.5 77.8 72.3 92.8 96.8 80.3 92.3 65.0

66.3 93.0

115.8 89.0

84.2

plot of

RS-2b(B) 8 7

1 1 4 1 1 1

6 7

8 1 5 9

1 18 8 5

1 1 4 8 7 81

1 0 4

1 0 9 9 0

1 0 4 7 3

7 4 1 0 4 1 3 0 1 00

9 5

Disease index

Actual1

1.75** 1.58** 1.96* 1.28** 1.36** 1.99* 1.46** 1.53**

1.47** 1.15** 1.79** 1.44**

1.07** 1.57** 1.18** 1.68**

1.55** 1.76** 2.44 1.34**

L57 5 . 4 3 # # 0.40 0.53

% of RS-2b(B)

131 1 18 1 4 6 9 6

101 1 4 9 1 0 9 1 1 4

1 1 0 8 6

1 3 4 1 0 7

8 0 1 1 7

8 8 1 2 5

1 1 6 131 182 1 0 0

117

(30) (40)

'Average severity of yellow wilt reaction, based on individual-plant ratings, using the scale: 0 = absence of yellow wilt symptoms and 5 = dead. * Disease index significantly below that of KWS-E, on the basis of LSI) (.05). **Disease index significantly below that of KWS-E, on the basis of LSD (.01). # # F greater than the 1% point.

V O L . 19, N o . 1 , M A R C H 1976 3 5

Table 4. — Comparison of sugarbeet lines for yellow wilt resistance; experiment no. 2, La Platina, 1973-74; 3 replications; results recorded Aug. 6-8, 1974.

Entry n o .

2 1 2 2 2 3 2 4

2 5 2 6 2 7 2 8

2 9 3 0 3 1 3 2

3 3 3 4 3 5 3 6

3 7 3 8 3 9 4 0

G e n e r a ! F

LSD (X)c

Seed no. or variety

71/3-1-6- L2 8 71/3-1-3-L29

-1.18 -LI 3

71/3-1-1-L5 71/3-1-5-L5 71/3-1-6-L20 71/3-42-3-L5

71/3-1-3-1.26 -L21

71/3-1-6-L24 71/3-1-1-1.4

71/3-1-3-L28 7 1/3-1-6-LI 1 71/3-1-3-L30 71/3-1-6-1.26

71/3-1-3-L4 71/3-1-6-1.25 KWS-K RS-2b(B)

mean

») for comparison LSD (.01) for comparison

No. of P e r

Description Actual 0 - E 0 -E 0 1

0 - E 1 0 -E 0

0 -E 0-E 0 - E 0 - E

0 - E 1 0 - E 0 -E

1 0 Comm. ck. Yel.

res.

of 3-of 3-

wilt ck.

1 12.7 85.3 94.3

120.7

80.0 1 12.7

87.7 80.7

89.0 93.0 84.3 92.3

40.0 75.0 74.3 88.3

111.0 89.7

123.7 97.7

91.6

-plot averages •plot averages

' plants plot % of RS-2b(B)

1 1 5 8 7 9 7

124

8 2 1 1 5

9 0 8 3

9 1 9 5 8 6 9 4

41 77

7 6 9 0

1 1 4 9 2

1 2 7 1 0 0

94"

Disease

Actual1

1.88** 2.1 1** 1.57** 1.53**

1.82** 1.82** 2.10** 1.73**

1.79** 1.35** 2.20* 2.46

1.77** 2.45 1.47** 2.11**

1.71** 2.16* 3.01 1.81**

1.94 2 . 9 5 # # 0.66 0.88

• index % of

RS-2b(B) 1 04 1 17

8 7 8 5

101 101 1 16

9 6

9 9 7 5

122 1 3 6

9 8 1 3 5

8 1 1 1 7

9 4 119 1 6 6 1 0 0

1 0 7

(36) (49)

1 Average severity of yellow wilt reaction, based on individual-plant ratings, using the scale: 0 = absence of yellow wilt symptoms and 5 = dead. *Disease index significantly below that of KWS-K, on the basis of LSD (.05). **Disease index significantly below that of KWS-E, on the basis of LSD (.01). # # F greater than the 1% point.

flowering and seed maturation occurred and within which natural trans­fer of pollen could have occurred by means of wind, insects, etc.; (c) a code number indicating the sugarbeet line serving as the immediate female parent of the new seed lot; and (d) the letter L (libre), indicating open pollination, followed by the female plant number. In the second position, 1 denotes the entire group of 1971-72 evaluation and selec­tion plots at La Platina in which selected plants were allowed to remain for seed production. The number, 42, pertains to a single isolated group at Linares. Third-position numbers denote the following Chil­ean lines described elsewhere in this report: 1 = RS-la, 2 = RS-lb, 3 = RS-2b, 5 = RS-2, and 6 = RS-3.

In the description column of each table: 1 indicates that the female plant had developed yellow wilt symptoms by about the end of the vege-

36 J O U R N A L OF THE A. S. S. B. T.

Table 5. — Comparison of sugarbeet lines for yellow wilt resistance; experiment no. 3, La Platina, 1973-74; 2 replications; results recorded Aug. 12-13, 1974.

No. of plants per plot Disease index

Entry Seed no. % of % of" no. or variety Description Actual RS-2b(B) Actual1 RS-2b(B) 41 4 2 4 3 4 4

4 5 4 6 4 7 4 8

4 9

5 0 5 1 52

5 3 5 4 5 5 5 6

5 7 5 8 5 9 6 0

71/3-1-6-L23 71/3-1-3-L22 71/3-1 -2- L4 71/3-1-6-L29

71/3-1-3-L16 71/3-1-6-L10 71/3-1-3-L17

73W601

73VV602

71/3-42-3-L4 71/3-1-5-L1 71/3-1-3-L12

71/3-1-6-L14 71/3-42-3-LI 71/3-1-6-L22 71/3-1-3-L23

-LI 9 71/3-1-6-L27 KVVS-E RS-2b(B)

General mean F LSD (.05) for comparison LSD (.01) for comparison

0-E 0-E 1 0 -E

0 -E 1 0 -E RS-2c (Ft. Col. inc.)

RS-1 orig. (Fi. Col. inc.)

0 1 1

0 - E 0 -E 0-E 0 - E

1 0 - E Comm. ck. Yel. wilt res. ck.

65.0 93.5 31.5 88.5

82.5 60.5 96.0

101.0

83.0

90.0 80.5 59.0

18.5 105.5 83.0 80.0

89.5 70.0

118.5 93.0

79.5

i of 2-plot averages i of 2-plot aver ages

7 0 101

3 4 9 5

8 9 6 5

1 0 3 I 09

8 9

9 7 8 7 6 3

2 0 1 13

8 9 8 6

9 6 7 5

127 1 0 0

8 5

2.68 1.53* 2.38 1.76*

1.84 2.36 1.82* 2.68

2.51

2.11 2.00 2.56

2.88 1.44** 2.05 1.36**

1.95 2.73 2.77 1.92

2.16 2.21# 0.94 1.28

1 4 0 8 0

1 24 9 2

9 6 1 2 3

9 5 1 4 0

131

1 10 1 0 4 1 3 3

1 5 0 7 5

107 7 1

1 0 2 142 1 4 4 1 0 0

113

(49) (67)

Average severity of yellow wilt reaction, based on individual-plant ratings, using the scale: 0 = absence of yellow wilt symptoms and 5 = dead. *Disease index significantly below that of KWS-E, on the basis of LSD (.05). **Disease index significantly below that of KWS-E, on the basis of LSD (.01). #F greater than the 5% point.

tative growth period (i.e. late in the fall or early in the winter) but appeared to be relatively resistant; 0-E means that the female plant appeared to be without yellow wilt symptoms up to about the end of the vegetative growth period but developed symptoms of the disease later on; and 0 pertains to plants which apparently remained free of the disease.

As was to be expected, the degree of precision, as indicated by F and LSD values, was highest in experiment 1 (4 replications), inter­mediate in experiment 2 (3 replications), and lowest in experiment 3 (2 replications). Nevertheless, meaningful results were obtained in all three experiments.

V O L . 19, N o . 1 , M A R C H 1976 37

Since RS-2b(B) and KWS-E were included as checks in all three experiments and since RS-2b(B) had shown clear evidence of resis­tance previously, a comparison of those two cultivars is of special interest. As shown in Tables 3, 4, and 5, the disease index for RS-2b(B) was lower than that for KWS-E in each of the three experiments rep­resented. In each of the experiments, 1 and 2, the difference was highly significant, being considerably greater than the value, LSD (.01). In experiment 3, with only two replications, the difference was not significant but closely approached the level of significance represented by LSD (.05). A detailed comparison of RS-2b(B) and KWS-E, with disease-grade frequency distributions, is presented in Table 6. Visual comparisons of the two lines in May, 1974 (Figure 3), were in keeping with the tabulated results in showing distinctly lower severity of yellow wilt attack in RS-2b(B).

Table 6. — Comparison of two sugarbeet lines in reaction to yellow wilt, showing disease-grade frequency distributions; La Platina, 1973-74.

Line KWS-E

RS-2b(B)

Exp .

no. 1 2 3

Average 1 2 3

Average

No. of repl.

4 3 2

4 3 2

Disease grade and average percent of rated population1

0 1 2 3 4 5 19.2 12.3 13.0 14.8 50.8 37.9 34.8

41.2

11.2 4.8 8.8 8.3

11.2 13.4 1 0.2 11.6

9.3 7.2 7.7 ------6.2 6.3 8.0 6 . 8

27.6 22.7 30.5 2 6 . 9 " 17.3 15.3 24.5

19.0

32.5 51.9 38.8 41.1 14.6 26.5 21.0

20.7

0.3 1.1 1.3

0.9

0.0 0.6 1.6 0 .7

Disease index 2.44 3.01 2.77

2.74 1.34 1.81 1.92

1.69 'Basis of grades: 0 = absence of yellow wilt symptoms; 5 = dead.

With reference to the 52 individual-plant progenies in experi­ments 1, 2, and 3 (Tables 3, 4, and 5), two points are of special interest. First, the disease index for each of 32 of them was very significantly lower (i.e. better) than that of KWS-E with a difference greater than LSD (.01). Second, although none of the individual-plant progenies were significantly lower than RS-2b(B) in disease index, the range of those progenies, particularly those derived from source 3 (RS-2b), strongly indicated that lines superior to RS-2b(B) in resistance can be developed. A comparison between one of the progenies and KWS-E, during the seed ripening period, is shown in Figure 4.

RS-2b(B) and the individual-plant progenies, as a class, were lower than KWS-E in stand (expressed as number of plants per plot, living or dead) at the time the disease ratings were made. This difference was due in part to low germination and/or inadequate seed supplies in some instances. Other, probably more influential factors were the

3 8 JOURNAL OF THE A. S. S. B. T.

Figure 3. — Comparisons of two sugarbeet lines in adjoining 4-row plots la Platina May 1974 Top KWS-E (left) and RS-2b(B) (BSDF photo BW74-1-11 May 6). Bottom: The same plots, viewed from the opposite end (KWS-E at right) (BSDF photo 74-G-38, May 10).

VOL. 19, N o . 1, MARCH 1976 39

Figure 4. — Comparison of 4-row plots of KWS-E (left) and an individual-plant progeny (entry 13) in 1973-74 experiment no. 1, La Platina, December, 1974. Plants that produced seed in entry 13 included those in which yellow wilt symptoms ap­peared by the end of the preceding winter as well as those in which the symptoms appeared later, if at all. Note devastation by yellow wilt in KWS-E. (Photo by Roberto Ehrenfeld K.)

annual tendency and the roguing of bolters in RS-2b(B) and many of the individual-plant progenies. An obvious net result of these factors was more space per plant for such material. A logical question may be whether the space advantage tended to result in a healthier appearance of plants and thus in lower disease-grade ratings than the same plants would have been given under full-stand conditions.

In order to study this question, the correlation coefficient (r) was computed for each of two sets of data. A total of 22 individual-plant progenies, evaluated in experiments 1, 2, and 3, had been obtained from the female parental source 3 (RS-2b) in the group of 1971-72 experimental plots at La Platina. Since more than one experiment was involved, both the stand and the disease index values were used as per­cent of RS-2b(B). On this basis, stand for the 22 progenies ranged from 41 to 124 (average 91.9) and disease indexes ranged from 71 to 134 (average 99.2). The r value computed from those data ( — 0.3152) was not significant according to the "t" test.

The same procedure was used tor the 17 individual-plant progen­ies that had been obtained from the female parental source 6 (RS-3) in the group of 1971-72 experimental plots at La Platina. In this instance,

40 JOURNAL OK THE A. S. S. B. T.

stand ranged from 20 to 1 1 5 (average 79.8) and disease index from 92 to 150 (average I22.1). The r value ( — 0.4377) was not significant.

If there had been a tendency for poor stands to result in low dis­ease indexes, then positive correlation coefficients would have been expected from the above computations. Since the correlation coeffi­cients actually were negative in both instances, it appears that no such relationship existed in the experiments involved. On the contrary, these results suggest the possibility that poor stands tended to result in some elevation of disease indexes. However, it should be emphasized that neither of the r values was significant and that definite conclusions regarding this point must await further study.

Discussion

The question could be raised as to whether the superior perfor­mance of RS-2b(B) and other breeding lines under natural yellow wilt exposure at La Platina, as shown in Tables 2, 3, 4, 5, and 6, could have been a result of insect preferences. Preliminary research on this subject was planned in 1972 but, for reasons of practicality, the work had to be postponed. However, a report of certain observations is pertinent. The differences in disease index, between RS-2b(B) and the commercial check variety, KWS-E, were about the same in the large plots of 1972-73 (Table 2) and the small plots of 1973-74. As pointed out else­where in this report, selected (infected) plants, left in place in the field, generally produced very little or no seed in earlier breeding work in Chile. A change in this pattern was observed in the late spring and summer of 1973-74 (i.e., November through January) when numerous selected (infected) plants of RS-2b(B), left in place in the 1972-73 eval­uation plots at La Platina, produced vigorous seed stalks and relatively satisfactory quantities of seed without the aid of antibiotics. A similar outcome was experienced a year later from such plants of RS-2b(B) and of the best individual-plant progenies listed in Tables 3, 4, and 5, cared for in the same way. Comparable plants of KWS-E produced essentially negligible growth during this reproductive period (Figure 4). These comparisons of reproductive development strongly indi­cated that post-infection resistance to yellow wilt is substantially higher in the best current breeding lines than in any breeding lines existing several years ago.

As indicated previously in this report, early experience in Argen­tina and Chile led to the conclusion that, although yellow wilt condi­tions were severe in the selection fields, plants without symptoms of the disease at the end of the growing season were of little if any value in breeding for resistance. Consequently, emphasis subsequently was placed on the selection of plants with symptoms but with apparent ability to grow in spite of infection. In view of recent developments including, especially, the results presented in this report, it now appears that reevaluation of the earlier conclusion is in order.

Voi. 19, No. 1, MARC. 1976 41

The results from the 1 973-74 experiments showed that one of the principal factors contributing to the superior performance of numer­ous lines was a relatively high percentage of plants classed as grade 0 (i.e. without yellow wilt symptoms), in contrast with the percentage of such plants in highly susceptible material. Such contrasts, with respect to KWS-E and RS-2b(B), are summarized for three experiments in Table 6. Similar contrasts, recorded in the date-of-planting study in the preceding year, may be seen in Table 2. Furthermore, it should be recalled that RS-2b(B), apparently the most resistant of the breeding lines tested repeatedly to date, is a product of several female plants, none of which showed symptoms of yellow wilt until late in the spring of the reproductive development period. In other words, those plants remained without symptoms throughout the season of vegetative growth (spring, summer, and fall), throughout the following winter, and throughout most of the following spring (see the section, "Materi­als, Methods, and Background Information," for further details). In view of these observations, it seems logical to conclude that, in some of the current breeding material, at least, plants without yellow wilt symp­toms at the end of the regular growing season, or at the end of the following winter, may be valuable for resistance-breeding purposes. Consequently, in our opinion, such plants should be included in the breeding program, in the foreseeable future, in addition to plants showing mild symptoms.

A strong annual tendency has been observed in many of the lines developed in the breeding program (e.g., see Table 2). This trend is not clearly understood. Bennett (4) has mentioned that the winter season at La Platina is too mild in some years to give adequate thermal induction to plants overwintering in the field. Thus, in such years, bolting-resistant genotypes tend to be eliminated from the breeding program. Another factor that undoubtedly contributed toward an­imalism in certain instances was the harvesting and subsequent use of seed from annual plants — i.e., plants that bolted in the field plots during the regular growing season.

The presence of plants with varying degrees of Swiss chard characteristics in breeding lines described in this report indicated that contamination by chard had occurred earlier in the development of those lines. The sources and mechanisms of such contamination are not known. However, Swiss chard apparently escaped from cultivation in vegetable growing areas in the general vicinity of Santiago and is now growing as a weed, probably largely as an annual, along irrigation ditch banks and in other places with adequate soil moisture. Windblown pollen from such plants and seed carried by irrigation water could be sources of contamination of sugarbeet material under certain conditions. It is conceivable that the annual tendency in the breeding lines resulted in part from such contamination. It also is

42 JOURNAL of THE A. S. S. B. T.

conceivable that natural selection over a long period of time has re­sulted in the development of substantial yellow wilt resistance in the "wild" chard, and that contamination by such material has contributed resistance to the sugarbeet breeding program. Although such a beneficial role is purely hypothetical at present, the possibility that resistant genotypes occur among wild chard populations in the vicinity of Santiago deserves thorough study. Exploration of this matter is planned.

It is unclear whether factors mentioned in the preceding parag­raphs adequately explain the annual tendency in the yellow wilt project material. In any case, the question arises as to whether a genetic linkage or some other causal relationship exists between yellow wilt resistance and the annual character. In our opinion, if some such relationship exists, it is not sufficient to interfere seriously with the selection and breeding program. Evidence in support of this conclusion may be observed in Tables 2, 3, 4, and 5.

The results presented in this report show conclusively that measurable progress has been made in the program of breeding sugarbeet for resistance to yellow wilt, and they indicate that further progress can be made. The apparent resistance of an introduction of B. maritima from Wembury Hay, England, suggests the possibility that valuable genes for resistance may be transferable to sugarbeet from that introduction and from other introductions of that wild species.

The long incubation periods in the insect vector (P. exitiosus) and the sugarbeet, and the erratic results of attempted inoculations of sugarbeet plants by means of cultures of that vector have interfered with breeding and other yellow wilt research in the past (3, 4, 6). The recent work of Urbina-Vidal and Hirumi (9), indicating the possibility of both virus and MIX) involvement in the expression of symptoms, may represent an important step toward a better understanding of the disease and some of the frustrations of the past. A vigorous program of etiological research could lead to the development of more effective as well as more efficient methods of breeding for yellow wilt resistance.

Summary Conclusive evidence was obtained in field tests of 1972-73 and

1 973-74 at the Estacic3n Experimental La Platina, near Santiago, Chile, that measurable progress had been made in breeding sugarbeet for resistance to yellow wilt. The level of resistance attained thus far in breeding lines is not high, but the evidence strongly indicates that further progress can be made.

Typically, yellow wilt infection interferes seriously with seed pro­duction. Consequently, in the past, infected sugarbeet plants with some evidence of resistance, as appraised at the end of the vegetative growth

VOL. 19, No. 1, MARCH 1976 43

period, generally produced very little or no seed under the most favorable agronomic conditions. In 1972, antibiotic treatments were used with apparent success in promoting seed production by a limited number of selected (infected) plants that had been left undisturbed in the 1971-72 evaluation plots at La Platina.

Until 1973, all attempts to obtain seed from sugarbeet plants that showed definite yellow wilt symptoms, at or near the end of the vegeta­tive growth period, and subsequently were transferred from the evalu­ation and selection plots to other locations, (ailed completely. With refinements in techniques, relatively satisfactory seed yields were ob­tained from selected (infected) plants that had been removed from the evaluation and selection plots in September (i.e., near the end of the winter), 1973, and treated repeatedly with the antibiotic, Terramycin. Thus, this much-needed breeding technique, heretofore unusable, now appears to be available to the breeding program.

In early selection and breeding (or yellow wilt, resistance in Argen­tina and Chile, it was concluded that plants without symptoms of the disease at the end of the vegetative growth period, under severe yellow wilt exposure, were simply escapees and consequently of little or no value for resistance breeding purposes. Evidence presented in this report indicated that, for at least some of the current breeding mater­ial, such plants may possess genes for resistance and should not be excluded from the breeding program.

One of three introductions of B. maritima appeared to have rela­tively high resistance to yellow wilt. This observation suggested that a useful but as yet untapped source of genes for resistance may exist in this wild species.

Acknowledgements The valuable cooperation of the Estacion Experimental La Platina

del Institute) dc Investigaciones Agropecuarias, near Santiago, Chile, is gratefully acknowledged. We appreciate the assistance received from the following staff members of the Agricultural Research Service, L".S. Department of Agriculture: Dr. C. W. Bennett, for much useful in­formation and advice; Drs. G. H. Coons, Dewey Stewart, and G. E. Coe for seed of wild species of Beta; Dr. J. S. McFarlane for seed of curly top resistant sugaibeet cultivars; and Drs. McFarlane and G. A. Smith for reproduction of certain sugarbeet lines involved in the research prog­ram. We also thank Dr. R. K. Oldemeyer, Great Western Sugar Com­pany, for seed of several broad-base cultivars for use as source material for selection purposes.

44 JOURNAL OF THE A. S. S. B. T.

Literature Cited (1) ARENTSEN S., SIGURD, ROBERTO EHREXFELD K., and JOSE M. PLAZA de los

REYES Z. 1 973. El cultivo de la remolacha azucarera en Chile. Tomo III — La marchitez amarilla de la remolacha. (A bulletin published by Industria Azucarera Nacional S.A., Santiago, Chile; 32 pp.)

(2) BENNETT, C. W. and C. MUNCK. 1946.Yellow wilt, of sugar beet in Argen­tina. J. Agr. Research 73:45-64.

(3) BENNETT, C. W ., F.J. HILLS, R. EHRENEELD K., J. VALENZUELA B., and C. KLEIN K. 1967. Yellow wilt of sugar beet. J. Am. Soc. Sugar Beet Tech-nol. 14:480-510.

(4) BENNETT, C. W. 1970. Selection and breeding sugarbcets for resistance to yellow wilt. Final report of research conducted under Cooperative Agreement No. 12-14-100-9334(34), between the Beet Sugar De­velopment Foundation and the Agr. Res. Service, U.S. Dept. of Agr., in cooperation with the Industria Azucarera Nacional S.A. 48 pp. (unpub­lished).

(5) BENNETT, C. \V. 1971. Selection and breeding sugarbcets for resistance yellow wilt. Supplemental repor t of research conducted unde r Cooperative Agreement No. 12-14-100-10,624(34), between the Beet Sugar Development Foundation and the Agr. Res. Service, U.S. Dept. of Agr., in cooperation with the Industria Azucarera Nacional S.A. 25 pp. (unpublished).

(6) EHRENEELD R., ROBERTO. 1968. Periodo de incubacion del virus de la marchitez (vellow wilt) de la remolacha en el vector, Parutanus exitiosu.s Reamer, y en la planta. Boletin temolachero Ano XII (No. 41):3-4.

(7) EHRENI•ELD K., ROBERTO. 1970. Estudio preliminar del efecto de cloro tetraciclina (aureomicina) sobre el causal etiologico de la "marchitez virosa" (vellow wilt) de la remolacha (Beta vulgaris L.). Agricultura Tecnica 30 (No. l):43-50.

(8) GASKILL, J. O. 1974. Selection and breeding sugarbcet for resistance to yellow wilt. Final report of research conducted under the cooperative arrangement indicated in (5), above. 39 pp. (unpublished).

(9) URBINA-VIDAL, C. and H. HIRL MI. 1974. Search for causative agents of the sugarbeet yellow wilt in Chile. J. Am. Soc. Sugar Beet Technol. 18:142-162.

The Effect of Sterile Cytoplasm on Curly Top Disease Resistance1

J. C T H E U R E R and D. L. M U M F O R D 2

Received for publication September 17, 1975

The discovery of cytoplasmic male sterility has made possible the large-scale, commercial production of hybrid varieties of many crops. In sugarbeets (Beta vulgaris L.), cytoplasmic male sterility provides the economically soundest means of developing superior varieties. Over 90% of the sugarbeet seed produced in the United States today is hybrid. It is produced with the aid of one source of cytoplasmic male sterility, discovered by Owen in 1945 (7).3 Cytoplasmic male sterility has been found in several open-pollinated varieties of sugarbeets, but no substantial evidence exists that these sources are significantly different (3).

The outbreak of southern corn leaf blight in 1970, its significance, and the fact that susceptibility to this disease was associated with T-type sterile cytoplasm focused attention on the genetic vulnerability of major crops. Corn (Zea mays L.) became a victm of the epidemic because T-type sterile cytoplasm had been used universally in hybrids and a new, more virulent strain of the pathogen Helminthosporium maydis suddenly emerged. As early as 1961, Mercado and Lantican (4) noted that in the Philippines corn hybrids with T cytoplasm were more susceptible to H. maydis than other hybrids. However, research workers in the United States failed to note this association (3).

Sugarbeet breeders arc concerned not only about the vulnera­bility of a single source of sterile cytoplasm, but also about the existence of a narrow genetic base for resistance to curly top, a virus disease spread by the sugarbeet leafhopper, Circulifer tenellus Baker. Curly-top devastated sugarbeet yields in the early 1920's and almost became an insurmountable barrier to the beet-sugar industry in the western United States (2). New, more virulent strains have been reported in recent years (1, 6). This demonstrates the ever-present potential for evolution of a more virulent strain of curly top.

This genetic vulnerability of sugarbeets suggested an investigation into the possible relationship of sterile cytoplasm and the curly top

1Cooperative investigations of the Agricultural Research Service, U.S. Department of Agricul­ture; the Beet Sugar Development Foundation; and the Utah Agricultural Experiment Station-Approved as journal paper no. 2005, Utah Agricultural Experiment Station, Logan, Utah.

2Research Geneticist and Plant Pathologist, Agricultural Research Service, U.S. Department of Agriculture, Crops Research Laboratory, UMC 63, Utah State University, Logan, Utah 84322.

3Numbers in parentheses refer to literature cited.

46 JOURNAL OF THE A. S. S. B. T.

disease in sugarbeets. The results of greenhouse and field tests at Logan, Utah are reported here.

Materials and Methods Seed of eight pollinators and their cytoplasmic male sterile equi­

valent inbreds were germinated in vermiculite in the greenhouse. Seedlings in the cotyledon stage of development were transplanted to 15-cm pots of soil. Five replicates of four plants each were planted for each variety. Viruliferous leaf hoppers were placed in small cages on each plant, and standard inoculation techniques and evaluation pro­cedures described by Schneider et al. (8) were followed. Isolate 66-10, more virulent than any other known strain of the curly top virus (6), was used as inoculum in this test. Each plant was classified visually on a 0-9 scale in which 0 represented a plant showing no curly top symp­toms and 9, a dead plant.

Replicated field tests of 12 sugarbeet inbreds and their cytoplasmic male sterile equivalents were also conducted in 1971 and 1972. The method used for evaluation of curly top in the field has been pre­viously described by Mumford (5).

Normal and sterile cytoplasm equivalents were compared by use of the standard t statistic.

Results and Discussion In the greenhouse, three fertile lines were slightly more suscep­

tible to curly top than their male sterile equivalent, and four other in­breds showed the opposite relationship (Table 1). The differences, however, were not significant.

Table 1. — Means of curly top reading (0 = no symptoms - 9 — dead plant) for cytoplasmic male sterile vs. normal fertile sugarbeet inbreds.

Greenhouse 1971 Field 1971 Field 1972 Inbred L3 L-53 L28 L29 L33 EL3 1 EL32 Al-10 Al-12 NB-1 F.C.504 F.C.506 F.C.601 Mean Calculated t

Fertile 6.0 4.4

— — 3.0

— 6.8 4.1

— 3.1 4.6

— 2.2 4.25

Sterile 6.4 4.4

— — 3.6

— 6.3 3.3

— 2.7 5.1

1.7 4.19

.43

Fertile

— — — 7.5

— — — 5.5

6.5 5.0

7.5 6.5 6.42

Sterile

— — — 7.0

— — — 5.0

5.5 5.5

7.5 6.5 6.17

.55

Fertile

— 5.3 4.6 4.0 3.0 8.0 7.0 4.3 5.6 4.0 5.6

5.6 5.18

<o

Sterile

— 5.3 4.3 3.6 3.0 8.0 7.0 3.6 5.3 3.6 6.0

— 5.0 4.97

21

VOL. 19, No. 1, MARCH 1976 47

Two r ead ings were m a d e on the field tests for each year , o n e in Augus t a n d t h e o t h e r i n S e p t e m b e r . T h e varieties w e r e similarly r a n k e d for each r e a d i n g , a n d only da ta for the S e p t e m b e r r e a d i n g arc-given in T a b l e 1. Fert i le a n d sterile equiva lents d id no t differ in cur ly t op scores in 1.971. In 1972 field tests, fou r steri le i n b r e d s had ident ical curly t op scores with the i r fertile c o u n t e r p a r t s . T h e o t h e r seven com­par i sons showed a slight but nonsignif icant d i f fe rence . In every case excep t o n e , t h e sterile equiva len t h a d a lower score than the fertile c o u n t e r p a r t . T h i s t r e n d , however , was p robab ly d u e to chance , be­cause no gene ra l consistency a m o n g the varieties was no t ed in t he t h r e e tests.

T h e varieties were original ly selected for wide d i f fe rences in curly t op res is tance. Differences be tween variet ies in all t h r e e tests w e r e significant. T h e s e da ta d e m o n s t r a t e that a p p a r e n t l y no association exists be tween the single sou rce of sterile cytoplasm in suga rbee t a n d t h e cur ly top disease inci ted by isolate 66-10 .

Sugarbeet , b r e e d e r s s h o u l d not b e c o m e c o m p l a c e n t with t h e a p p a r e n t negat ive association be tween sterile cytoplasm a n d curly t op disease. C o r n b r e e d e r s in t h e Uni t ed States failed to n o t e any asso­ciation be tween cytoplasms a n d H . maydis unti l t he c o i n blight e p i d e m i c of t he 70*s (3). S u g a r b e e t r e sea rche r s shou ld be aler t for new sources of sterile cy toplasm a n d for new, m o r e virulent s t ra ins of curly t op , a n d they shou ld c o n t i n u e to test t h e m for any association tha t could cause p r o b l e m s similar to co rn leaf bl ight .

Abstract

T h e o u t b r e a k of s o u t h e r n co rn leaf bl ight in 1970 a n d the asso­ciation of disease susceptibili ty with T - type sterile cytoplasm focused a t t en t ion on the genet ic vulnerabi l i ty of major c rops .

T h i r t e e n cytoplasmic male sterile a n d equiva len t po l l ina tor in­b reds of s u g a r b e e t (Beta vulgaris L.) we re c o m p a r e d to d e t e r m i n e any association be tween t h e single s o u r c e of steri le cytoplasm in suga rbee t s a n d susceptibility to t h e curly t op virus disease. Field a n d g r e e n h o u s e tests in 1971 a n d 1972 with 66-1 0, the most v i ru len t strain of the virus k n o w n to d a t e , ind ica ted no d i f fe rence be tween the equ iva len t n o r m a l a n d sterile geno types in the i r susceptibili ty to cur ly top .

Key w o r d s — Suga rbee t disease, cytoplasmic male sterility, gene t ic vulnerabi l i ty , virus disease

Literature Cited

(1) BENNETT, C. W. 1 963. Highly virulent, strains of curly top virus in sugar-beet in western United States. J. Am. Soc. Sugar Beet Technol. 12: 515-520.

4 8 JOURNAL OF THE A. S. S. B. T.

(2) CARSNER, EUBANKS and F. V. OWEN. 1947. Saving our sugarbeets. In Science and Farming. U.S. Dept. of Agr. Yearbook, U.S. Government. Printing Office, Washington, pp. 357-362.

(3) Committee on Genetic Vulnerability of Major Crops. 1972. Genetic Vulnerability of Major Crops. Nat. Acad. Sci., Washington, D.C.

(4) MERCADO, A. D., J R . and R. M. L A M I C A N . 1961. The susceptibility of cytoplasmic male sterile lines of corn to Helminthosporium maydis Nish and Mig. Phillipine Agriculturist 45:235-243.

(5) MUMFORD, D. L. 1974. Procedure for inducing curly top epidemics in field plots. J. Am. Soc. Sugar Beet Technol. 18:20-23.

(6) MUMFORD, D. L. and VV. E. PEAY. 1970. Curly top epidemic in western Idaho. J. Am. Soc. Sugar Beet Technol. 16:185-187.

(7) OWEN, F. V. 1945. Cvtoplasmicallv inherited male-sterility in sugar beet. J. Agr. Res. 71:423-440.

(8) SSHNEIDER, C. L., A. M. JAFRI, and A. M. MURPHY. 1968. Greenhouse testing of sugarbeet for resistance to curly top. J. Am. Soc. Sugar Beet Technol. 14:727-734.

Effects of Early Terminal Irrigation and Late Nitrogen Application on Yield and

Incidence of Root Rot in Sugarbeets in the Imperial Valley1

C. F. EHLIG, R. D. L E M E R T , R. Y. REYNOSO, and C. K. ARTERRERRY 2

Received for publication January 8, 1976

Introduction Sugarbeets (Beta vulgaris L.) are planted in the Imperial Valley,

California, in August, September, and October for harvest in April through July. Roots are harvested daily for immediate processing be­cause roots stored at high temperatures break down internally and decay rapidly. In scattered fields root rot. incidence has been great be­fore late harvest in some years but not in others. This has often been associated with (a) high nitrate (NO3) concentrations in unrotted roots in the same fields, (b) relatively wet fields, and (c) relatively cool tem­peratures in winter and early spring. The absorption near harvest of nitrogen (N) applietl to the sugarbeets in fall and winter has been blamed for the high nitrate concentrations in the late-harvested roots.

Growers often terminate irrigations 4 to 8 weeks before harvest to dehydrate the roots. Low N content and water stress are needed to retard root growth before harvest for spring-harvested sugarbeets, whereas low N content and cool temperatures are needed to retard root growth for fall-harvested sugarbeets. Retarding root growth be­fore harvest is necessary to allow the sucrose to accumulate in the roots thereby raising the sucrose concentration (5)3. Terminating irriga­tions early also reduces the probability of root rot in fields with root rot histories. Negligible effects on total sucrose have been reported from afternoon wilting (4) and by terminating irrigations for 3 or 4 weeks before harvest at Phoenix, Arizona (2) or for 30 days in Kern County, California (3). The effects on sucrose yield and root rot of long periods of water stress in the Imperial Valley were questioned because of the high temperatures and the extreme leaf deterioration possible before harvest of early-irrigation-terminated sugarbeets.

'Contribution of the Imperial Valley Conservation Research Center, Agricultural Research Service, Western Region, USDA, Brawley, California.

2Plant Physiologist, Agricultural Research Technician, Agricultural Research Technician, and Soil Research Helper, respectively.

3Numbers in parentheses refer to literature cited.

50 JOURNAL OF THE A. S. S. B. T.

We conducted experiments at the Imperial Valley Conservation Research Center to determine the effects of late applied N and early irrigation termination on yield, sucrose concentration, total sucrose, nitrate concentration, and the incidence of root rot. in late-harvested sugarbeet roots.

Methods and Materials Sugarbeets (cv. USH 10) were seeded in a dry silly clay loam soil

(typic torriorthent of the mixed, calcareous, hyperthermic family) on one row beds with 76 cm between row centers. After a previous wheat crop, the 1.5-ha field was plowed to a 0.5 m depth and irrigated. Nitrogen and phosphorus were broadcast at 84 and 46 kg/ha, respec­tively, and disced into the top 15 cm of soil before bed formation. The field was sprinkler-irrigated on October 1 to 3, 1973, to initiate seed germination. A herbicide, Roneet4 was applied at 31/2 kg/ha with the irrigation water during the later part of the irrigation. The field was resprinkled on October 7. Seedlings were thinned to a 20- to 25-cm spacing on October 23 to 26. An additional 184 kg N/ha (as urea) was sidedressed on November 5. The field was furrow irrigated on eight dates between November 12 and May 17, inclusively. Irrigation water was applied for about 24 hours whenever cumulative cvapotranspira-tion from sugarbeets in an adjacent weighing lysimeter reached 10.2 cm water, following a method that has been described previously (1, 8). Pesticides were applied as required for controlling insects, spider mites, and powdery mildew.

An additional N application and an additional irrigation were compared individually and in combination with no additional N appli­cation or irrigation. The additional N was applied at 1 60 kg/ha (as urea) immediately before an April 3 irrigation. The additional irrigation was applied on June 3. Four replications of a split-split-plot design were used. Within each replication, the N split was within the same plant rows and the irrigation split was between different plant rows which permitted applying the same irrigation treatment over the entire length of a plant row. Individual plots for the N application were 15 m long x three rows wide. A similar-size plot, without the N application, was also marked. The irrigation treatment was applied to an additional three or four rows to each side of the N plots.

Petioles were sampled on April 1 7 and June 13 and dried at 70°C. Petiole NO3-N concentrations were determined colorimetrically utilizing the diazotization method (Technicon industrial method IND-33-69W)4. The sugarbeets were observed weekly from April until harvest for root rot. Roots were harvested from a 2 m x 2 row section of each plot on June 25. The harvested roots were topped, washed, weighed, and sampled for determinations of sucrose and nitrate con-

4Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable.

V O L . 19, N o . 1 , M A R C H 1976 51

centrations. Percent sucrose was determined with a polarimeter. Brei nitrates were determined by the diphenylamine method with a rating of 1 (no color, low nitrate) to 5 (maximum color, high nitrate). Inci­dence of root and crown rot were also noted.

Experimental Results Favorably warm temperatures (Table 1) contributed to rapid seed

germination, emergence, and growth. Plant leaves completely covered the soil by mid-December. Visible symptoms of foliar N-deficiency appeared in March. Warm April and May temperatures promoted rapid plant uptake and utilization of the late-applied N. Leaves of the plants that received the late N application regreened rapidly after April 3. These plants produced large green leaves in April and May and successively smaller and lighter green leaves in June. Plants that did not receive the late X-application produced successively smaller and lighter green leaves in April and May, followed by small and erect leaves in June.

Table 1. — Summary of air temperatures recorded at the Imperial Valley Conser­vation Research Center, Brawley, California during the growing season for sugarbeets from October 1973 to June 1974, inclusively.

Temperature Mean Mean Meant Normal

Month Max Min Daily Max Min Mean °F

October 92.0 54.8 73.4 November 77.2 45.7 61.4 December 72.1 37.7 54.9 January 66.8 41.2 54.0 February 72.9 39.0 55.9 March ' 78.5 47.4 63.0 April 85.3 52.2 70.4 May 93.8 57.6 75.7 J u n e 106.4 67.3 86.9

arithmetic mean Based on tempera ture averages for 15 years in 1973 and 16 years in 1974.

Average-leaf-petiole NO3-N concentrations were below 800 ppm in unfertilized plots and above 7000 ppm in the fertilized plots on April 17, 2 weeks after the late N application (Table 2). Average leaf petiole NO3-N concentrations were equally low in all plots on June 13.

Terminal irrigations on May 17 and June 3 were applied 38 and 2 1 days, respectively, before harvest on June 25. The older plant leaves wilted slightly during afternoons about 2 weeks after the last irriga­tion. Older leaves wilted successively more severely with time after the last irrigation until they started dying. The oldest leaves then died progressively as the roots became increasingly less able to absorb water from an increasingly drier soil to meet transpirational losses.

101 93 79 78 80 90 93 109 1 17

45 34 32 27 31 34 43 49 56

73.7 62.1 53.8 52.9 57.9 62.1 67.9 75.7 83.4

52 JOURNAL OF THE A. S. S. B. T.

Table 2. — Petiole nitrate on May 17 and June 13 and number, weight, sucrose content, and nitrate level of sugarbeet roots harvested on June 25, 1974. A late nitrogen application of 160 kg/ha was applied on April 3.

Terminal Irrigation Date

May 17

June 3

Significance*

Late Application

Y e s N o Y e s N o

Roots/ Plot

15.8 15.8 15.2 15.5

Root Weight

kg/plot

32.8 30.8 32.5 33.0 N S

Brei Sucrose

%

14.7 15.6 14.1 14.4 N S

Total Sucrose

kg/plot

4 . 8 4 . 8 4 . 6 4 . 8 N S

Brei t

NO3-

2 . 8 1.8 2 . 5 1.8 N S

Petiole NO3--N

4/17 6/13

ppm

7029 a 185 766 b 160

7 1 1 5 a 180 756 b 128

P = 0.01 NS *Significance at P = 0.05, unless oerwisc noted. t B r e i nitrate was rated on a scale of 1 (very low) to 5 (high).

At harvest, leaves covered about rds of the soil surface lor the late terminal irrigation and about ½ for the early terminal irrigation, regardless of whether they had received the late N fertilization. Only small leaves were alive which showed little or no visible symptoms of wilting. Roots remained turgid at all times. The soil cracked exten-sively upon drying.

Average weight, sucrose content, and nitrate content of the har-vested roots were equal for all treatments (Table 2). An average plot root weight of 32 kg at 14.7% sucrose yielded 106 MT /ha roots and 15.6 MT/ha total sucrose. Root nitrate concentrations were relatively low. Incidence of rotten roots was negligible, although there was an early stage of crown rot in about 20% of the harvested roots, regardless of treatment. The crown rot appeared as darkened areas or small volumes of soft tissue adjacent to crown cavities. The causal organ-ism(s) was not identified although we suspected Rhizoclonia. Root yield was unaffected by the slight crown rot, because the crowns were removed in the harvest procedure.

Discussion and Conclusions Climatic factors favored rapid growth throughout the growing

season. Favorably warm temperatures promoted excellent and rapid seedling emergence and growth, rapid uptake and utilization of the late applied N, and high root and total sucrose yields. The high root yield (106 MT/ha) precluded a high sucrose concentration. By present concepts that the leaf petiole NO3

--N concentration should have been below 1000 ppm for 60 to 90 days before harvest (5), on April 17 the leaf petiole NO3

--N concentration was unsatisfactorily high for the late-fertilized plots and sufficiently low for the unfertilized plots for harvest on June 25.

Results from this experiment suggested that residual concentra-tions within the root zone of N applied judiciously to sugarbeets during fall and winter should not cause high NO3

--N concentrations

VOL 19, No. 1, MARCH 1976 53

in late harvested roots. We cannot recommend an application of 160 kg N/ha in April according to our data; but it did not cause a high NO3

--N concentration in the roots on June 25. The additional N was used in leaf production during April and May. The equally high total sucrose in both the fertilized and unfertilized plots suggest that the large green leaves photosynthesized sufficiently more sucrose than the light green leaves to compensate for the extra photosynthate re-quired to produce the additional leaves. Data of Krantz and MacKenzie (7) support this conclusion, although there was additional root growth in their experiments with late N applications to sugarbeets planted in late October and early November. In their experiment, leaf petiole NO3--N concentrations were below 500 ppm by May 31, with N appli-cations as high as 90 kg/ha in March plus 90 kg/ha in late April. Their root yields were only about V2 of our root yields. These experimental data suggest that we reevaluate the source or cause for the high NO3-N of unrotted roots from fields with high incidence of root rot.

Terminating irrigations early as in this experiment did not dehy-drate the roots and raise the sucrose percent as much as we had anticipated. Unpublished data from a preliminary experiment in spring of 1972 had indicated that roots dehydrated when water was withheld for 22 days, as compared with 13 days before harvest. Roots were harvested at 2 week intervals from March 28 to June 21. During the 2-week period ending on April 26, 22 days after last irrigation, root weight increased from 63 to 67 MT/ha or 5% and sucrose concen-tration increased from 12.4 to 14.8%. This compared with a root weight increase from 54 to 63 MT/ha or 18% and a sucrose concentra-tion increase from 1 1.8 to 12.4% during the previous 2-week period when sugarbeet roots were harvested 13 days after last irrigation. When the harvest date was returned to 13 days after irrigation in the succeeding 2-week period, root weight increased from 67 to 84 MT/ha or 26% and sucrose concentration decreased from 14.8 to 13.9%. During each of the 2-week periods, average total sucrose production was relatively constant at 113 to 131 kg/ha/day. These small differences in average total sucrose production were explained by an increase in photoperiod.

In our experiment, root dehydration was equal for both terminal irrigation dates. The roots remained turgid and dehydrated only slightly before the older leaves died to balance plant water losses with a decrease in plant water absorption, as the soil dried. Further de-dydration may not be desirable since rot may occur more frequently in farmers' fields to flaccid roots than to turgid roots. Terminal irriga-tion date in this experiment did not affect total sucrose.

We did not establish a causal relationship between high root NO3

--N concentrations and incidence of root rot. If the crown rot had continued to develop and enlarge for an additional 2 to 4 weeks, root yield and sucrose concentration might have decreased markedly in

54 JOURNAL OF THE A. S. S. B. T.

spite of low root NO3--N concen t ra t ions . Root rot was not significant

in f a rmers ' fields until t he last 2 weeks in July. F u t u r e e x p e r i m e n t s should be c o n t i n u e d until the e n d of Ju ly and should inc lude a season with co lder fall a n d win ter t e m p e r a t u r e s than those in o u r e x p e r i m e n t . T h e s e should p rov ide g r e a t e r cont ras ts t han were ob ta ined in this e x p e r i m e n t .

A c k n o w l e d g e m e n t

T h e a u t h o r s t h a n k the Agr icu l tu ra l D e p a r t m e n t o f Holly S u g a r C o r p o r a t i o n , Brawley, Cal i fornia for the i r analyses for sucrose a n d n i t ra te concen t ra t ions in the sugarbeet roots .

Literature Cited (1) EHULIG, C. F. and R. D. LEMERT. Water use and productivity of wheat

under five irrigation frequencies, (unpublished) (2) ERIE, L.J. and O. F. FRENCH. 1968. Water management of fall-planted

sugar beets in Salt River Vallcv of Arizona. Trans, of Amer. Soc. Agric. Eng. 1 1(6).-792-795.

(3) FERRY, G. V., F . J . HILLS, and R. S. LOOMIS. 1965. Preharvest water stress for Valley sugar -beets. Calif. Agr. 19(6): 13-14.

(4) JENSEN, M. E. and L.J . ERIE. 1971. Irrigation and Water Management p. 190-222. In Advances in Sugarbeet Production: Principles and Prac-tices edited by R. T. Johnson, J. T. Alexander, G. E. Rush, and G. R. Hawkes. Iowa State Univ. Press. Ames, Iowa.

(5) HILLS, F . J . and A. ULRICH. 1971. Nitrogen Nutrition p. 112-135./In Advances in Sugarbeet Production: Principles and Practices, edited by R. T. Johnson, J. T . Alexander, G. E. Rush, and G. R. Hawkes. Iowa State Univ. Press. Ames, Iowa.

(6) KOHL, R. A. and J. W. GARY. 1969. Sugarbeet Yields Unaffected by Afternoon Wilting. Am. Soc. Sugar Beet Technol. 15:416-421.

(7) KRANTZ, B. A. and A.J . MACKENZIE. 1954. Response of Sugar Beets to Nitrogen Fertilizer in the Imperial Valley, California. Proc. Am. Soc. Sugar Beet Technol. 8:36-41.

(8) LEMERT, R. D. and P. R. NIXON. 1972. A weighing Lysimeter for Water Management Studies. Winter Meetings Am. Soc. Agr. Eng., Chicago, 111., Paper No. 72-771.

Climatic Periods and Thresholds Important To Sugarbeet Production

K. JAMES FORNSTROM and LARRY O. POCHOP1

Received for Publication January 21, 1976

The dependence of crop yield on climatic factors has been recog-nized for main years. For example, temperate zone plants generally undergo vegetative growth from 30°F to about 100°F but optimum growth is obtained in the range of 77-86°F (5)2. Went (6) found in greenhouse studies that the optimum temperature for sugarbeets was 68-73°F while sugar percentage varied inversely with temperature. Me obtained the lowest sugar percentage at 86°F, which was the highest temperature of his study. Bauer et al., (1) found that root dry matter production was related to growing degree units which were calculated using a 40°F base temperature and a maximum temperature of 86°F.

The average weather conditions generally determine adaptability of a particular crop for a particular area, while variations in crop yields can be attributed largely to year-to-year variations in weather, Indentification of early season climatic patterns which significantly affect crop production may indicate management decisions to com-plete production of crops. This paper describes the application and results of a particular method of correlating short term weather pat-terns with the production of sugar beets for three stations in Wyoming.

Procedures Caprio's (2) method of using a chi-square statistic to provide a

qualitative association between climatological data and yield was em-ployed. A subjective method of selecting the most important periods for sugar beet production was then applied by following procedures similar to those proposed by Cornia, et al., (3) for winter wheat pro-duction.

Data Sugarbeet yield data were obtained for the Powell (for the years

1932 th rough 1972), Wheat land (1944-1972), and Worland (1940-1972), Wyoming areas from the factory manager or field man

1Associate Professor and Professor, Agricultural Engineering Division, University of Wyoming, Laramie, Wyoming 82071. Acknowledgement: Yield data was provided by Stan Walter and Herb Pearcy, Great Western Sugar Co., and by Roger Hill, Rodd Fullmer and Al Edwards. Holly Sugar Co. Published with the approval of the Director, Wyoming Agricultural Experiment Station, as Journal Article 804.

2Numbers in parentheses refer to literature cited.

56 JOURNAL OF THE A. S. S. B. T.

for each area. The yields were expressed in both tons of beets per acre and sugar percentage. A linear correlation of yield as a function of years was used in an attempt to define yield trends due to technological advances and changes in management. Each of the years was then categorized according to "good," "normal," or "poor" yields. "Good" years were defined as years with the largest yields in excess of the trend line while "poor" years were defined as years with yields which were the smallest percentage of the trend line. The number of years defined as "good" and "poor" years was determined by ranking the years accord-ing to the above definitions and then selecting at the best break in the ranking to give 5 to 1 0 years in both the "good" and "poor" categories. This was equivalent, to placing approximately one-fourth of the years in each the "good" and "poor" categories with the remainder categorized as normal. Yields, in tons of beets and sugar percentage, as a function of years for Powell are shown in Figures 1 and 2, respec-tively. The trend line parameters and categorized yield years for identification of climatic periods for each of the three stations are given in Table 1.

Daily occurrences of maximum and minimum temperatures and pcrcipitation were used in the chi-square analysis. The climatic data were obtained from the National Weather Servicer, NOAA, stations in the respective areas.

Figure 1. — Tons of beets per acre as a function of year for Powell.

VOL. 19, No. 1, MARCH 1976 57

Figure 2. — Percent sugar as a function of year for Powell.

Yield- Weather Association

Indices of Association, i.e., qualitative measurements of crop re-sponse to weather, were determined between sugarbeet yields (tons of beets per acre and percent sugar) for each of the climatic parameters of daily maximum and minimum temperature and precipitation for each station. Indices were calculated for each week between January 8 and December 23 using climatic data for that week plus the week previous and the week after, giving a 21 day period associated with each index.

Caprio's (2) method, which uses a chi-square statistic to compare frequency of daily occurrences of weather events in good (poor) years with frequencies in normal years, was employed. Maximum and minimum temperatures and precipitation were divided into class inter-vals. Five degree Fahrenheit temperature intervals were used. The precipitation intervals (in inches) were: 0.00, trace, 0.01-0.03, 0.04-0.08, 0.09-0.15, 0.16-0.24, 0.25-0.35, 0.36-0.48, 0.49-0.63, 0.64-0.80, 0.81-0.99, 1.00-1.49, 1.50-1.99, and greater than 2.00. A chi-square value was calculated for each interval using the accumulated frequency of occurrences for all previous intervals. The chi-square statistic used was:

58 JOURNAL OF THE A. S. S. B. T.

Where: k = class interval number,

On k = observed occurrences in normal years at class interval k, Tn k = theoretical number of occurrences for normal years at class

interval k, Og, k = observed occurrences in good (or poor) years at class interval k, Tg. k = theoretical number of occurrences for good (or poor) years

at class interval k.

The index of association for any 21-day period is defined as the highest chi-square value for that period. Intervals with less than 14 occurrences were ignored. An index was significant at the 1% level if its absolute value was greater than or equal to 6.6, i.e., the 1% level for a chi-square distribution with 1 degree of freedom. A significant index of association indicated that for the week in question, the good (poor) year's weather was significantly different than the weather in normal years. The temperature or precipitation value of the upper (or lower) limit of the interval having the largest chi-square value is defined as the threshold of the weather parameter.

- C a t e g o r i z e d y i e l d years f o r i d e n t i f i c a t i o n o f c l i m a t i c p e r i o d s .

Trend Line: Constant Slope R2

Good Years*

Poor Years*

Powell (32-72)

Tons Percent Beets Sugar

3.19 0.171 0.69

32 35 37 40 67 71

39 42 44 45 40 48 50 54 64 70

19.27 0.041 0.24 34 39 51 55 56 62 63 64 65 67 48 52 61 69 70

Wheatland (41-72)

Tons Percent Beets Sugar

2.72 17.99 0.163 -0.008 0.24 0.01

43 44 47 45 49 50 63 60 72 68

54 4 2 55 48 56 52 62 54 64 55 70 69

Worland (40-72)

Tons Beets

-1.12 0.284 0.68

40 41 69 71

45 48 61 62 64 65

Percent Sugar

10.77 -0.006

0.01 43 51 53 54 56 68

40 4 1 42 48 61 65 71

* Years not listed were categorized as normal years.

V O L . 19, N o . 1 , M A R C H 1976 59

Selection of Periods

O n c e indices of association were calculated for all weeks a n d w e a t h e r p a r a m e t e r s , i t was necessary to select the pe r iods c o n s i d e r e d mos t i m p o r t a n t to s u g a r beet p r o d u c t i o n . As discussed by Corn ia , et. al., (4) these pe r iods cou ld be selected e i the r objectively, by cons ide r ing all o r an a r b i t r a r y p e r c e n t a g e o f t h e indices which w e r e statistically significant, or they could be selected subjectively by us ing cr i ter ia es tabl ished for this p u r p o s e . Fo r this s tudy the subjective m e t h o d was used , with the cr i te r ion that an i m p o r t a n t pe r iod was o n e h a v i n g significant indices for bo th h i g h a n d low values of the wea the r p a r a m e -ter . For e x a m p l e , an i m p o r t a n t p e r i o d would be o n e with significant indices for bo th h igh a n d low m a x i m u m t e m p e r a t u r e s . Th i s i s f u r t h e r i l lus t ra ted in F igu re 3 which is a p lot of the i ndex of association as a funct ion of weeks of t he year for m a x i m u m t e m p e r a t u r e in p o o r years (with yields e x p r e s s e d in tons of beets) at Powell. T h e significant indices a r e ind ica ted by the h a t c h e d areas . A negat ive index indicates a deficit of t e m p e r a t u r e s above or below the th re sho ld while a positive index indicates an excess o f t e m p e r a t u r e s above o r below the t h r e sho ld . T h e per iod of Ju ly 7 to A u g u s t 10 is an i m p o r t a n t pe r iod acco rd ing to the cr i ter ia set up since an excess o f m a x i m u m t e m p e r a t u r e s g r ea t e r t han 70°F is significant while a deficit of m a x i m u m t e m p e r t u r e s less than 70°F is also significant in p o o r years . T h e pe r iod of S e p t e m b e r 7 - 28 is not cons ide red i m p o r t a n t , however , since t h e r e is no c o m p l e m e n t to t he excess o f m a x i m u m t e m p e r a t u r e s g r e a t e r t han 80°F.

F i g u r e 3 . — A s s o c i a t i o n b e t w e e n h i g h and l o w m a x i m u m t e m p e r a t u r e a n d tons o f b e e t s , p o o r years v s n o r m a l years , 1 9 3 2 - 1 9 7 2 , P o w e l l , W y o m i n g .

60 JOURNAL OF THE A. S. S. B. T.

Results and Discussion No important periods were identified for precipitation. This is

probably as expected in an irrigated area unless there is a correlation between precipitation and temperature or field operations. Appar-ently delays and losses experienced due to excess precipitation at planting and harvest of sugarbeets do not occur frequent enough or do not cause large enough losses to become significant in this type of analysis. Obviously losses of this type do occur, but probably not to the magnitude to turn a good year into a normal year or a normal year into a poor year.

Important periods indentified for temperatures for Powell, Wor-land and Wheatland are shown in Tables 2, 3, and 4, respectively. In an attempt to generalize, nonconflicting periods and thresholds indicate that:

1. Good yields of tons of beets are obtained when there is an excess of maximum temperatures less than 90°F in July and August and less than 70°F in September.

2. Poor yields of tons of beets are obtained when there is an excess of maximum tempertures less than 60°F in May and greater than 84°F in July and when there is an excess of minimum temperatures less than 35°F in May and less than 55°F in July.

3. Good sugar percentages are obtained when there is an excess of maximum temperatures less than 70°F in October and less than 48°F in November and when there is an excess of minimum temperatures greater than 50°F in August and less than 30°F in October.

4. Poor sugar percentages are obtained when there is an excess of maximum temperatures less than 80°F in late May and early June, less than 90°F in August and less than 48°F in November and when there is an excess of minimum temperatures less than 45°F in August.

It should be noted that the generalizations are for three specific stations. This is not an attempt to obtain a growth model for sugar beets, but rather an attempt to differentiate good and poor yield years for specific locations based on climatic differences for those areas.

Summary The dependence of sugarbeet production on temperature and

precipitation has been investigated for three Wyoming stations. The most important periods have been defined by applying Caprio's (2) method of using a chi-square statistic to provide a qualitative associa-tion between climato logical data and yield.

Results for each of the stations and generalizations for the three stations are presented. No important precipitation periods were identified. Most of the temperature periods which depressed yields were excesses of warm temperatures, especially for tons of beets per acre.

Table 2. — Climatic periods and thresholds identified for Powell sugarbeet production.

Period Temperature Occurrences and Levels Effect

Jan. 1 -Jan. 28

Jan. 1 -Feb. 18 Feb. 19- Mar. 17 Mar. 11 - Mar. 31 Apr. 22 - May ] 1

May 12-June 15 May 12 - June 15 May 19 - June 29

May 19 - June 15

July 7 - A u g . 10

July 14- Aus- 24 July 28-Sep t . 7

Aug. 4 - Aug. 31 Sept. 29 - Oct. 19

Sep). 29 - Oct. 19 Oct. 20 - Nov. 9

Oct. 2 0 - Nov. 16

An excess of max. temp, above 34°F and a deficit of max. temp. below 33°F

An excess of min. temp, below 15°F and a deficit of'min. temp, above I9°F

An excess of max. temp. al)ove 34°F and a deficit of max. temp, below 1()°F An excess of max. temp, above 54°F and a deficit of max. temp, below 50"F An excess of max. temp, above 74°F and a deficit of max, temp, below 65°F

An excess of max. temp, below 75°F and a deficit of max. temp. alxue 79°F

An excess of min. temp, below 50°F and a deficit of min. temp, above 49C;F

An excess of max. temp, above 79°F and a deficit of max. temp, below 70°F

An excess of min. temp, atxnc 49°F and a deficit of min. temp, below 45°F

An excess of max. temp, above 89"F and a deficit of max. temp, below 80" F

An excess of min. temp, above 59°F and a deficit of min. temp, below 50°F

An excess of max. lemp. below 85°F and a deficit of max. temp. above 89°F

An excess of max. temp, below 90°F and a deficit of max. temp, above 89°F

An excess of max. temp, below 45°F and a deficit of max. temp, above 74°F An excess of min. temp, below 30°F and a deficit of min. temp, above 34°F

An excess of'min. temp, below 20°F and a deficit of'min. temp, above 34°F

An excess of max. temp, below 50°F and a deficit of max. temp, above 49°F

Good Yield*

Good Sugar %

Good Sugar % Poor Yield Poor Yield

Poor Sugar %

Poor Sugar %

Poor Yield

Poor Yield Poor Yield

Poor Yield Good Yield

Poor Sugar % Good Sugar %

Good Sugar % Good Sugar%

Good Sugar %

*Yield refers of yield in tons of beetls per acre

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Table 3. — Climatic periods and thresholds identified for Wheatland sugarbeet production.

Period Temperature Occurrences and Levels Effect

Jan. 8 - Jan. 21 An excess of max. temp, above 39°F and a deficit of max. temp, below 30°F Poor Yield*

Jan. 8 -Jan. 28 An excess of min. temp, alxne 19°F and a delicit of mm. temp, below 0°F Good Yield

Jan. 22 - Jan. 28 An excess of max. temp, above 44°K and a deficit of max. temp, below 35°F Good Yield

Feb. 12 - Feb. 25 An excess of max. temp, below 45°F and a delicit of max. temp, above 54°F Good Yield

Mar. 11 - Mar. 24 An excess of max. temp, above 59°F and a deficit of max. temp, below 25°F Poor Sugar %

Mar. 18 - Mar. 24 An excess of min. temp, above 34°F and a deficit of max. letup, below 20°F Poor Yield

Apr. 8 - Apr. 14 An excess of max. temp, below 60° F and a delicit of max. temp, above 59°F Poor Sugar %

Apr. If) - Apr. 28 An excess of max. temp, above 59C'F and a deficit of max. temp, below 00°F Good Sugar %

Apr. 22 - May 1 An excess of min. temp. alxne 34°F and a deficit of max. temp, below 35°F Good Sugar %

Apr. 29 - May 18 An excess of max. temp, below 60°F and a deficit of max. temp, above 79°F Poor Yield

May 5 - May 18 An excess of min. temp, below 35°F and a delicit of min. temp, above 44°F Poor Yield

June 23 - Aug. 10 An excess of min. temp, below 55°F and a delicit of min. temp, above 59°F Poor Yield

July 7 - July 13 An excess of max. temp. Ixdow 90°F and a deficit of max. temp, above 89°F Poor Sugar %

July 21 - Aug. 3 An excess of max. temp, below 85°F and a delicit of max. temp, below 94°F Good Yield

Aug. 4 - Aug. 10 An excess of min. temp, below 55°F and a deficit of min. temp, above 54°F Good Yield

Aug. 1 I - Aug. I 7 An excess of min. temp, above 51°F and a deficit of min. temp, below 15°F Good Sugar %

Aug. 1 8 - Aug. 31 An excess of max. temp, below 80F and a deficit of max. temp, above 94°F Poor Sugar %

Aug. 18 - Sept. 7 An excess of min. temp, below 45°F and a deficit of min. temp, above 54°F Poor Sugar %

Sept. 15 - Oct. 5 An excess of max. temp, below 70°F and a deficit of max. temp, above 74°F Good Yield

Oct. 13 - Oct. 19 An excess of max. temp, below 65°F and a delicit of max. temp, below 74::F Good Sugar %

Nov. 24 - Nov. 30 An excess of max. temp, above 11°F and a deficit of max. temp, below 15;F Poor Sugar %

Nov. 24 - Dec. 7 An excess of min. temp, above 29°F and a delicti of min. temp, below 25=F Good Sugar %

* Yield refers ro yield in tons of beets per acre.

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Table 4. — Climatic periods and thresholds identified for Worland sugarbeet production.

Period Temperature Occurrences and Levels Effect

Jan. 15 - [an. 21 Mar. 25 - Apr. 7 Mai. 21 - Apr. 14

Apr. 8 - Apr. 14

Apr. - Apr. 28 June 9 - June 15

June 9 - June 22

July 21 - Aug. 24

Aug. 18-Sept. 7

Sepl. 8 - Sept. 11

Sept. 8 - Sept. 21 Sept. 22 - Sept. 28

Sepl. 22 - Sept. 28 Sept. 22 - Oc:t. 5 Nov. 10- Nov. [W

An excess of max. temp, below 13°F and a deficit of max. temp, alxne 5VI An excess of max. temp, above 51°F and a deficit of max. temp, below 55° F

An excess of inin. temp, below 35°F and a deficit of min. temp, above M4°F

An excess of min. temp, above 24:;F and a deficit of min. temp, below 25°F An excess of min. temp, below 35°F and a deficit of min. temp, above 34° F

An excess of max. temp, below 80° F and a deficit of max. temp, above 84°F

An excess of min. temp, below 45°F and a deficit of min. temp, above 60cF

An excess of min. temp, below 50°F and a deficit of min. temp, alxne 54°F An excess of min. temp, above 44°F and a deficit of min. temp, below 15°F

An excess of max. temp, above 84°F and a deficit of max. temp, below 55°F An excess of mm. temp, above 41°F and a deficit of min. temp. below 30°F An excess of max. temp, above 81CF and a deficit of max. temp, below 55°F

An excess of max. temp. alx)ve (i9°F and a deficit of max. temp, below 65°F

An excess of max. temp, above 7f F and a deficit of max. temp, below 70°F An excess of max. temp, below :WF and a deficit of max. temp, alxne 54°F

Good Sugar % Poor Yield*

Good Yield

Good Sugar % Good Yield

Poor Sugar %

Poor Sugar % Good Yield

Poor Yield

Poor Yield Poor Yield Poor Yield Poor Sugar %

Good Yield Good Sugar %

*Yield refers to yield in tons of beets per acre.

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64 JOURNAL OF THE A. S. S. B. T.

Literature Cited (1) BAIER, A., T. HEIMBUSH, D. CASSEL, and E. ZIMMERMAN. 1975. "Pro-

duction potential of sugarbeets under irrigation in the west Oakes Irrigation District." North Dakota State University, Ag. Exp. Sta. Bulletin 498.

(2) CAPRIO, J. M. 1966. "A statistical procedure for determining the asso-ciation weather and non measurement, biological data." Agr. Meteor. 3: 55-72.

(3) CORNIA, R. L., L. O. POCHOP, and C. F. BECKER. 1973. "Selection of climatic periods important to winter wheat production in eastern Wyoming." Wyo. Agr. Exp. Sta. Res. Journal 69.

(4) CORMA, R. E., and E. O. POCHOP. 1973. "Multivariate approach to climatic data analysis for predicting crop production." Am. Soc. of Agr. Engr., Paper No. 73-45 18.

(5) MEYER, B. D., D. B. ANDERSON and R. H BOHNING. 1960. Introduction to Plant Physiology. D. Van Nostrand and Co., Inc., Princeton, New Jersey.

(6) WENT, F. W. 1957. Environmental Control of Plant Growth . Ronald Press Co., New York.

A Growing Mulch Tillage System To Reduce Wind Erosion Losses of Sugar Beets1

K. JAMES FORNSTROM and R E X D. BOEHNKE.2

Received for publication March 8, 1976

Wind erosion is a major problem in the establishment of sugar beets in some areas of Wyoming as well as other parts of the Great Plains. Sugar beets are most susceptible during the establishment period when potential wind is the highest, i.e., May and June. Cultural methods which leave residues on the surface appear to have the great-est potential for combating this erosion problem.

The objective of this study was to develop a tillage system which would protect sugar beets during their stand establishment period of growth. During the study comparisons of wind erosion potential, stand establishment, yield, water use, and energy requirements were made between the conventional tillage practices now in use and the mulch tillage method under study.

The mulch system used in this study is based on a system used in Eastern Colorado (3)3 which employs rotary strip tillage. In this Col-orado area sugar beets generally follow corn which was harvested for grain and thus there is an abundance of remaining residue for erosion protection.

With preceding crops of sugar beets, potatoes, beans, or corn for silage, there is not enough remaining residue to provide erosion pro-tection. Establishment of a satisfactory mulch has thus also been a goal of this project.

The area in which this study was conducted is near Pine Bluffs, which is in the southeastern corner of Wyoming. Irrigation of the areas in the study was by sprinkler, mostly center pivot. Conventional tillage practices for establishment of sugar beets under sprinkler irrigation in this area generally consist of: plowing, roller harrowing, bedding (start-er fertilizer applied), planting (pre-emergence herbicide also applied and incorporated), and an early cultivation to control wind erosion. Many of the soils of the area arc quite sandy and thus formation of clods for erosion protection by cultivation is not always successful since the clods are broken down by sprinkler irrigation or precipitation.

1Published with the approval of the Director, Wyoming Agricultural Experiment Station, as Journal Article 825.

2 Associate Professor, Agricultural Engineering, University of Wyoming, Laramie, Wyo-ming, and Agricultural Engineer, Hawaiian Agronomics, Tehran, Iran.

3Numbers in parentheses refer to literature cited.

66 JOURNAL OF THF. A. S. S. B. T.

Initial Mulch Culture Methods In 1972, a field seeded to fall rye was used for the mulch. The rye

was 10-12 inches high when sprayed with Paraquat two days before the sugar beets were planted. A 10 inch band was rotary tilled and the beets were planted in this band.

Two problems were encountered in using the fall seeded rye. First, the rye was not completely killed and severe competition with the sugar beets resulted. Problems with control of a fall seeded crop were also found by Carey et al., in Idaho (1). Second, a compacted layer was evident which hindered root development of the sugar beets.

In 1973, two types of tillage procedures were tried with spring seeded bailey used as the growing mulch. The barley was solid seeded in a field which had been spring-plowed and in a field which had only been disked after the previous year's potato crop. Strip rotary tillage and planting were done in one operation. The barley between the rows was removed with a powered rotary tiller when the beets were in the four to six leaf stage.

The barley did successfully protect the sugar beets from wind erosion losses during 1973. Using Woodruff's (7) method of calculat­ing potential soil loss, the conventionally tilled fields had a soil loss rate of 49 tons/A/yr as compared to 17 tons/A/yr for the mulch tilled fields. The wind erosion was severe enough that the beets in approximately 25% of the adjacent conventionally tilled field were lost.

Although wind protection was obtained in the 1973 plots, several other problems were encountered when using the barley as a mulch. Control of the barley in the beet row was a major problem. The strip tillage at planting did not remove all the barley, due to unevenness of barley germination time, insufficient tillage depth and perhaps trans­planting some of the small seedlings. The barley in the row competed with the beets for water and nutrients causing a poor beet stand, increased labor for removal, and decreased yields. A problem was also encountered in using a selective thinner. The flat planting method left the sugarbeet row in a depression and thus it was difficult for the thinner knives to cut the beets out. Compaction seemed to again be a problem in the plots which were not plowed.

Stands and yields of the 1973 plots are shown in Table 1. Yields were depressed in the mulch plots due to the barley competition and compacted layer which restricted root growth.

Barley Mulch Method The method of mulch culture, which evolved from the early

studies, employs conventional tillage followed by a bedding-barley planting operation in which the barley is planted in the area between the future beet rows. Conventional tillage is used to reduce the com-

VOL. 19, No. 1, MARCH 1976 67

pacted layer formed during the harvest operation of the previous crop. The barley is planted between the rows for ease of removal, and a bed is formed for ease of cultivation and thinning. Spring barley is used so that water and nutrient competition is not severe during time of emergence.

This system was successfully employed in the 1974 plots (average size of 7 acres). The barley was planted about two weeks before the beets were planted using a converted grain drill. The single disk openers were changed so that they threw the soil toward the future beets rows. The openers thus threw up a small bed while planting the barley between the future beet rows. A close-up of one row of the converted grain drill is shown in Figure 1.

The barley planted in rows coinciding with the beet rows provided wind protection for the beets and was much easier to cultivate out with the rotary cultivator. A beet row with the adjacent barley rows is shown in Figure 2. The cultivation operation to remove the barley is shown in Figure 3. No barley was planted in the "guess" rows and it would have been helpful if none had been planted in the middle row which coin­cides with the rotary clutivator's gearbox.

One plot of the conventionally tilled beets had about 907c of its area destroyed by wind erosion in 1974. The other conventionally tilled plot was not destroyed because of its small size while the barley mulch provided protection of the mulched plots. The potential soil loss rates were 22 tons/A/yr and 1 7 tons/A/yr, respectively, for the conven­tional plots while the soil loss rates for the mulch plots were 6 tons/A/yr and 5 tons/A/yr. These observations when using Woodruffs method of

6 8 JOURNAL OF THE A. S. S. B. T.

Figure 1. — Close-up converted grain drill used to apply starter ferti­lizer, form a small bed and sow barley adjacent to the future sugarbeet row.

Figure 2. — Emerging sugar beet seedlings with adjacent wind-protec­tive barley mulch.

VOL. 19, No. 1, MARCH 1976 6 9

Figure 3. — Powered rotary cultivator removing wind protective bar­ley mulch.

loss calculations would indicate that a rate of soil movement greater than 17 tons/A/yr would damage the emerging sugarbeet seedling.

Emergence percentage was superior in the mulch-tilled plots , i.e. 60% vs 39%. The smaller emergence percentage also reflects the losses incurred by wind erosion, even though the replanted conventional plots had fully emerged at the time of the initial stand count. Yields of the 1974 mulch plots were equal to the conventional plot which did not have to be replanted (16.3 tons/A) while the plot which was replanted was significantly less (10.7 tons/A) than the other three plots. Compar­ing tillage methods, the mulch plots averaged 16.7 tons/A while the conventional plots averaged 13.6 tons/A. Final stand counts and yields are given in Table 1.

Two fields of beets were grown by t he coopcrator in 1975 using the barley-mulch system. These two erosion-prone fields were compared with two similar size fields (approximately 35 acres each), on which conventional methods were employed. The barley-mulch system will prevent, wind erosion losses as shown in 1974, but careful management of the barley as well as of the beets is required. In 1975, the inter-seeded barley failed to prevent sugarbeet losses due to wind erosion as the barley did not. have sufficient growth by the time the beets were emerging and damaging winds occurred. Comparison of heat units (40°F base temperature) indicated that only 175 heat units had been attained for barley growth by the time the beets were emerging in 1975, compared to 300 heat units in 1974 when the barley did successfully prevent losses. Clod management in the conventional fields success­fully protected them from losses although their erosion potential was also less. The yield differences were mainly a reflection of the loss of

70 JOURNAL or THE A. S. S. B. T.

stand in the mulch fields (one field was replanted one month after the original planting). The mulch fields averaged 9.0 tons/A while the conventional fields averaged 13.1 tons/A. All fields suffered hail dam­age.

Water Requirements In conjunction with development of the barley-mulch method,

Settemcyer (5) studied the water requirements for the conventional and mulch systems. His objective was to correlate the water require­ments of the conventional and mulch systems to determine the compet­ition between the sugar beets and barley for the available water.

The amount of actual evapotranspiration was estimated by use of soil moisture readings and rainfall and/or irrigation water data for the periods between soil moisture readings (approximately one week in­tervals).

The evapotranspiration for the 1973 conventional and mulch plots is shown in Table 2. When the bailey was still growing in the mulch plots, the mulch plots used about 0.02 in./day more water than the conventional plots. Due to the early competition from the barley in the beet row the mulch beets were delayed in their growth and had poorer yields. The total water use by the mulch plots was about equal with the conventional plots.

The evapotranspiration for the 1974 conventional and mulch sugarbeet plots as well as barley alone is also shown in Table 2. Again

Table 2. —Evapotranspiration (inches) for 1973 and 1974 sugar beet (conventional and barley mulch) and barley plots, Pine Bluffs, Wyoming (5).

VOL. 19, No. 1, MARCH 1976 71

the early season water use was higher for the mulch plots but the total water use was the same for both tillage methods. It thus appears that the barley does not increase the total water use if it is kept out of the row and is eliminated before the boot stage of growth, and that early water management is more critical to prevent loss of beet emergence.

Energy Considerations Due to the energy shortage it was of interest to find the energy

requirements of the mulch tillage system. Previous work has been done on other tillage operations but very little on the rotary cultivation used in mulch tillage practices.

A one row, fully instrumented, rotary tiller was constructed to measure the energy consumption (Figure 4). The chassis and rotor assembly were similar to the rotary tiller used in the mulch studies. The power train of the instrumented tiller included a hydrostatic transmis­sion so that a wide range of rotor speeds could be obtained for the same forward speed. Instrumentation included a torque meter and revolu­tion counter mounted on the tiller, and drawbar-pull strain gage link, wheel revolution counter and fuel flow meter on the tractor.

The average energy consumption for strip cultivation was 2.1 hp-hr/A, when tilling with similar depth and speed conditions as the large machine. A range of 1.2-3.0 was found using different depths and rotor speeds. The soil type in the study is classified as a sandy loam texture.

Total energy requirements for the two systems were compared by using Hunt's data (4) on field machinery power requirements. Average seasonal energy requirement of conventional tillage amounted to 45 hp-hr/A while for the mulch tillage system the energy requirement amounted to 47 hp-hr/A, i.e., an additional 2 hp-hr/A for powered rotary cultivation. A completely no tillage system would require 23 hp-hr/A for harvesting. For the sprinkler system used in this study, 975 hp-hr/A was required for application of the average water requirement (6). For estimating water application energy, the total head was 270 ft of water (190 ft for pressure), the combined pump and motor efficiency was estimated as 65%, and the irrigation efficiency was estimated as 75%. Thus, it appears that the real potential for reducing field energy under this type of irrigation is not in the actual tillage system itself but rather indirectly by perhaps increasing infiltration such that a lower pressure requirement for the sprinkler system would be required.

Discussion The growing barley mulch system can be successfully employed to

protect sugar beets from wind erosion losses. In the area studied it

72 JOURNAL OF THE A. S. S. B. T.

Figure 4. One row, instrumented rotary tiller used to measure energy requirements.

worked best when conventional tillage practices were followed and the barley was planted between the future beet rows. Little extra water or energy were required.

More study of the system does need to be undertaken, however, to define management decisions needed for the system to be practically implemented. In 1975, it was shown that insufficient protection by the barley is obtained if the barley does not have enough growth before the beets are planted. On the other hand, if the grain is too large when the beets are planted, removal and competition are problems. A study of barley growth as a function of heat units may solve this timing problem. A model exists (2) for the heat units required to obtain sugar beet emergence. If the number of heat units required to grow the barley to a stage such that it provided protection was known, the number of heat units required between barley planting and beet plantingcould then be inferred and used as a management tool. Herbicidal control of the growing mulch was not attempted in this study. If adequate control of the mulch with herbicides were shown, fall seeded crops would be practical. Without this control it is felt that fall seeded crops become unmanageable before the beets are large enough to remove the grow­ing mulch. Nitrogen competition has been observed in other studies (1) and perhaps was present to a small degree in the these studies. Future application of growing mulch systems would require definition of the nitrogen competition problem and the additional fertilization re­quirement.

VOL. 19, No. 1, MARCH 1976 73

Cultivar Blends for Buffering Against Curly Top and Leafspot Diseases of Sugarbeet1

R A L P H E. FINKNER 2

Received for publication April 19, 1976

The argument is often advanced that populations composed of genetically diverse types should have increased stability of perfor­mance over fluctuating environments. Conceptually, an array of geno­types in a heterogeneous population possesses the ability to utilize a variety of environmental niches and should respond in a relatively uniform way to exigencies of the environment.

Multiline cultivars of some small-grain crops have been developed to control diseases and increase yields. The concept was also applied in 1971 when the outbreak of Helminthosporium maydis on T-cyto-plasmic male-sterile lines in corn and the limited number of corn hybrids with resistant normal cytoplasm encouraged the use of seed blends.

Multilines are blends of different genotypes each of which, in the simplest case, contains a different gene of resistance. Browning and Frey (2)3 reviewed the use of multilines in small-grain disease control. They support the development of multilines. Researchers at CIMMYT are also using the multiline approach in developing new wheat cultivars (6).

There is considerable evidence that reproductive ability of several crops is enhanced by variations in genotypic association. For example, enhancing effects were observed for particular sets of genotypes in wheat (1, 7), barley (1), potatoes (4), and soybeans (3, 5, 9, 1 1).

Scheifele (10) and Josephsen et al. (8), working with blends of T-cytoplasm and N-cytoplasm hybrid corn, found some buffering effect of N-cytoplasm against the southern corn leaf blight disease. The buffering percentage, as measured by yield, depended on the proportion of T-cytoplasm plants in the blends. Fehr and Rodriguez (5), working with soybeans, found all their blends produced highest yields when the highest yielding cultivar made up at least 70 percent of the blend.

The yield and disease performance of a blend can be evaluated by its compensating response. Compensatory response is the deviation of a blend's actual disease reaction from the mean weighted disease

1Journal article 588. Agricultural Experiment Station. New Mexico State L'niversitv, Plains Branch Station, Clovis, New Mexico. 2Prof"essor of Agronoim , Plains Branch Agricultural Experiment Station, Clovis, New Mexico. 3Numbers in parentheses refer to literature cited.

VOL 19, No. 1, MARCH 1976 75

reaction (expected disease reaction) of the component cultivars in pure stand. Four types of compensatory responses in a blend have been identified: neutral, complementary, overcompensatory, and undercompensatory. Neutral and complementary responses result in a blend performance that is equal to the expected performance. An overcompensatory response represents a greater performance and an undercompensating response a lower performance than expected.

Sugarbeet cultivars most generally planted on the High Plains of eastern New Mexico are hybrids from a curly top-resistant parent and a leafspot-resistant parent. These hybrids are intermediate in resistance to both diseases. Severe losses may occur as a result of epi­demics of leafspot and curly top, either separately or concurrently, in the same year.

The objective of this study was to determine whether seed blends could be used as a buffer against both curly top and leafspot diseases of sugarbeets.

Materials and Methods Replicated field tests were conducted each year from 1972 to

1974 at the Plains Branch Station, Clovis, New Mexico. The descrip­tion of the seven entries included in all years were:

Curly top-resistant hybrid (CTR) Cercospora leafspot-resistant hybrid (LSR) Holly Hybrid 10 (CTR x LSR) (check) US II9B (CTR- and virus yellows-resistant) (check) Blends 3-CTR to 1-LSR

1-CTR to 1-LSR 1-CTR to 3-LSR

The blends were based on the percentage of viable seeds. The severity of sugarbeet diseases is sometimes associated with

the physiological development of the plant. Therefore, it seemed de­sirable to plant these blends at three different times (early, medium, and late). Table 1 gives the three dates of planting, the amount of fertilizer applied, number of irrigations, and the harvest dates for the three tests.

Plots were 20 feet long with two rows on a 40-inch bed. The rows were approximately 12 inches apart. The complete plot (40 linear

Table 1. — Planting dates, fertilizer applied, number of irrigations, and harvest dates for sugarbeet tests, 1972 to 1974, Plains Branch Station, Clovis, New Mexico.

Date of Planting Fertilizer No. of Date of Year 1st 2nd 3rd N-P-K Irrigations Harvest 1972 2/25 3/23 4/19 200-0-0 9 12/20 1973 3/7 3/28 4/18 200-0-0 10 10/31 1974 3/15 4/16 5/1 200-0-0 12 11/26

76 JOURNAL or THE A. S. S. B. T.

feet) was harvested for yield, and a 12-beet sample was saved for sucrose determination. Each test contained five replications.

The incidence of culy top was reported as a percentage of in­fected plants from an entire plot. Curly top percentages were trans­formed (arc-sine) for statistical analysis.

Leafspot ratings were made on a scale from 1 to 9. Ratings of 1, 2, or 3 were considered resistant; 4, 5, and 6 intermediate; and 7, 8, and 9 susceptible.

Results and Discussion The disease reactions and yield components for the sugarbeet

cultivars tested are shown in Figures 1 through 5. Every year, sucrose yields differed significantly between planting dates. Early-planted beets produced more sucrose. Only one significant interaction was detected between cultivars and planting dates during the three vears of testing. Therefore, the cultivar means were averaged over the three planting dates and the five replications and these means were used to construct the various graphs.

Figure 1 shows the curly top percentages of the cultivars for each year and the average across three years. Curly top incidence was light in 1973 and only moderate the other two years. The blend cultivars did not deviate greatly from the expected, but the observed curly top percentages tended to be below the expected. The 1 : 1 ratio and the 1-CTR:3-LSR ratio were 14 and 10 percent, respectively, below the three-year average of 45 observations. The response of blends to curly top infection showed only a slight buffering effect.

The compensatory response of blends to Cercospora leafspot disease is shown in figure 2. These responses were considered to be slightly overcompensatory as most of the observed disease readings for the blends were below the expected. The buffering effect for the 3-CTRT-LSR averaged 13 percent.

The yields in tons per acre are given in figure 3, sucrose percen­tage in figure 4, and pounds of sucrose per acre in figure 5. These responses were very erratic between vears but tended towards neutral or undercompensation. The three-year average sugar yield of the LSR cultivar in pure stand outproduced all its component blends, the CTR cultivar, and the local check variety IIII10. However, the check hybrid US H9B produced the highest three-year average of sugar per acre (figure 5). Although US H9B gave an excellent yield in this area, it tended to be low in quality, measured by sucrose percentage (figures 3 and 4).

The three-year average yield of blends in this study was lower than the highest yielding LSR cultivar and showed only a slight buffer-

VOL. 19, No. 1, MARCH 1976

Check Hybrids Percent

X = Holly HH10 30

• = US H9B

- Hoily HH

- US H9B

Figure 1. — Mean curly top percentages for sugarbeet blends, 1972, 1973, 1974 and combined years. Plains Branch Station. (Expected line is the linear relationship between the two cultivars in pure stands.)

7 8 J O U R N A L OK T H E A. S. S. B. T.

Figure 2. — Mean leaf spot disease rating of seed blends, 1972, 1973, 1974 and combined years. Plains Branch Station. (Expected line is the linear relationship between the two cultivar in pure stands.)

VOL. 19, No. 1, MARCH 1976

Figure 3. Mean tonnage yields for sugarbeet blends, 1972, 1973, 1974 and combined years. Plains Branch Station. (Expected line is the linear re­lationship between the two cultivar in pure stands.)

80 JOURNAL OF THE A. S. S. B. T.

Figure 4. Mean sucrose percentages for sugarbeet blends, 1972, 1973, 1974 and combined years. Plains Branch Station. (Expected line is the linear relationship between the two cultivar in pure stands.)

VOL. 19, No. 1, MARCH 1976

Figure 5. Yield of sucrose (pounds per acre) for sugarbeet blends, 1972, 1973, 1974 and combined years. Plains Branch Station. (Expected line is the linear relationship between the two cultivar in pure stands.)

82 JOURNAL or THE A. S. S. B. T.

VOL. 19, No. 1, MARCH 1976

Meritorious Service Award Presented

to CHARLES L. SCHNEIDER

Dr. Schneider has been a member of the Society since 1950. He has served the ASSBT as chairman of the entomology and plant pathology section at the 1 3th and 1 7th General Meetings and as a member of the publications committee for the Biennium 1964-65. He has been an author or coauthor of 20 papers published in the ASSBT Proceedings and Journal. He began work with sugar beets in 1948 as a plant pathologist with the U.S. Department of Agriculture, Agricultural Research Service at St. Paul, Minnesota. Subsequently he was stationed at Beltsville, Maryland; Logan, Utah; and East Lansing, Michigan. He has cooperated in the development of sugar beet varieties with im­proved resistance to blackroot, leafs pot, and curly top diseases. He has studied the epidemiology of some of the principal sugar beet diseases in the humid areas of the United States and has aided in the develop­ment of chemical and cultural methods for their control.

Dr. Schneider is a native of Illinois and attended the University of Minnesota where he earned the M.S. degree in 1953 and the Ph.D. in 1956. He served with the anti-aircraft artillery in the Army from 1941 to 1946.

Mr. Tingley has been a member of the Society since 1942. He has served three Biennia on the Advisory Council (now the Board of Directors); he has served on the Nominating Committee for three Biennia, (two of them as chairman); he has served on the General Arrangements Committee; and he has authored or coauthored six papers published in the ASSBT Proceedings. He started with the beet sugar industry in 1924 as sample carrier and henchman while attend­ing college at Fort Collins, Colorado. Upon graduation he started his professional employment with Holly Sugar Corporation in 1929 as an agricultural fieldman at Swink, Colorado. In 1935 he was transferred to California where he lived at Sacramento, Chico, Stockton, and San Mateo, serving Holly for thirty years as Agriculturist, District Agricul­turalist, Western Agricultural Manager and Pacific Coast Manager. In 1964 he was transferred to the home office in Colorado Springs where he retired in 1 969 as Assistant to the Vice President — Agriculture. He served as Director and President of the Beet Sugar Development Foundation, as Director and President of the Western Seed Production Corporation, and as a director of the West Coast Beet Seed Company for 24 years and its president for 7 years. Since retirement he has served as a consultant with Manexec, Inc. of Colorado Springs, Direc­tor on Management Board of Navajo Agricultural Products Industry, on the Board of the Colorado State Univeristy Alumni Foundation, as a board member of the Pikes Peak Chapter American National Red Cross and as a Board Member of Christmas Unlimited of Colorado Springs.

84 JOURNAL OF THE A. S. S. B. T.

Meritorious Service Award Presented

to ROBERT J. TINGLEY

Dr. Oldemeyer has been a member of the Society since 1952 and has served three Biennia on the Awards Committe, twice as its chairman; once on the Editorial Committee; and once as chairman of the Genetics and Variety Improvement section. He has authored or coauthored twenty-three papers published in the ASSBT Proceedings or Journal. Although he was reared on a sugar beet farm near Brush, Colorado, he officially began work with sugar beets in 1 950 when he joined the staff of the Agricultural Experiment Station of the Great Western Sugar Company at Longmont, Colorado. He has been there since, serving consecutively as Plant Breeder, Chief Plant Breeder, Director of Ag­ricultural Research, Director of Seed Production and Processing, and Manager of Variety Development at what is now the Agricultural Research Center. He has lead his company's programs in breeding, developing, and producing those highly productive monogerm hybrid monogerm varieties now known as the Mono Hy brand of sugar beet seed.

Dr. Oldemeyer majored in Agronomy at Colorado State Univer­sity and earned his M.S. and Ph.D. degrees at the University of Wiscon­sin, majoring in Genetics with a minor in Plant Pathology. He is a charter member of the Grower — GW Joint Research Committee, Inc. and has an appointment as Staff Affiliate, Department of Agronomy, Colorado State University. He is a member of several social, profes­sional, and honorary societies and is active at the local and national levels of his church.

Meritorious Service Award Presented

to ROBERT K. OLDEMEYER

85 VOL. 19, No. 1, MARCH 1976

Mr. Miles has been a member of the Society since 1950. He has served as chairman of the Nominating Committee and has been awarded the Forty-Year Veteran Award. He began his career in the beet sugar industry working campaigns for the Holly Sugar Corpora­tion while still in high school at Torrington, Wyoming. Following graduation from Stanford University with a degree in Physical Sci­ences (Chemical Engineering), in 1936 he became a student for Holly Sugar Corporation at Hamilton City, California. He was a Shell Chem­ical employee for a short period of time, returning to Hamilton City as Extra Station Man, Station Relief, and Relief Foreman. In October 1940 he joined active military service, returning to Hamilton City in 1945 to become Beet End Foreman. He was transferred to Brawley, Calif, where he became Assistant Construction Superintendent and Shift Superintendent. From 1954 to 1964 he served as Factory Man­ager for Spreckels Sugar Company at Spreckels, California; then re­turned to Holly at the main office of Holly Sugar Corporation as Assistant General Superintendent. He subsequently became General Superintendent, Vice President and General Superintendent and Senior Vice President — Operations. In the military service, Mr. Miles served overseas in India, Egypt, Libia, Tunisia, Sicily, Italy, Germany, Normandy and Northern France. He retired from reserve status with the rank of Lieutenant Colonel, U. S. Air Force.

Meritorious Service Award Presented

to GEORGE W. MILES, JR.

JOURNAL OF THE A. S. S. B. T. 86

Dr. Dickenson has been a member of the Society since 1956, has served one Biennium as a director, one Biennium on the Nominating Committee, was program chairman for the 8th General Meeting, and has been author or coauthor of three papers in the ASSBT Journal. He joined the beet sugar industry in 1953 at Sheridan, Wyoming as Plant Breeder and Pathologist. In 1962 he was transferred to Tracy, Califor­nia to become Assistant Director of Agricultural Research; in 1966 he was promoted to Director of Agricultural Research. He was moved to the main office in Colorado Springs in 1971 to assume responsibility for the company's beet quality improvement program. He is on the Boards of Directors for the Western Seed Production Corporation, West Coast Beet Seed Company, and the Beet Sugar Development Foundation. Dr. Dickenson is a native of Illinois; he attended the University of Illinois from 1946-50 where he earned a B.S. degree in General Agriculture and an M. S. degree in Agronomy and Botany. He was a graduate student at the University of Minnesota from 1950-53 where he was awarded the Ph. D. with a major in Plant Genetics and a minor in Plant Pathology. He is a member of the American Society of Agronomy, Crop Science Society of America, Genetics Society of America, and American Phytopathological Society.

Meritorious Service Award Presented

to DONALD D. DICKENSON

87 VOL. 19, No. 1, MARCH 1976

Mr. Hartmann has been a member of the Society since 1956 and has served two Biennia as a member of the Board of Directors, repres­enting the West Coast. He started his career with the beet sugar industry with Spreckels Sugar Company at Manteca, California, as a Trainee. This was in 1936, immediately following his graduation from Stanford University with a bachelor's degree in Chemical Engineering. He later became Chief Chemist at Woodland and Spreckels; was a traveling chemist; then became Shift Superintendent and Factory Superintendent at Spreckels. He was promoted to General Superin­tendent and Director of Industrial Relations at the main office in San Francisco and subsequently given the responsibility of Production Manager. He authored two chapters in each edition of McGinnis's Beet Sugar Technology and the paper "The Calcium Saccharate Process" published in Sugar Technology Reviews. He was co-inventor with J. Rodney Earl (deceased), Richard A. McGinnis, and Walter O. Ber­nhardt (deceased) of the Spreckels Automatic Saccharimeter. Mr. Hartmann retired in January of 1973 but has continued active in the industry as instructor at the Beet Sugar Institute and as an impartial member of the Acceptance Panel for the factory at Renville, Min­nesota. He has been a member of the chemical fraternity Alpha Chi Sigma since 1935 and the American Chemical Society since 1939. He is a Registered Professional Engineer in Chemical Engineering in the state of California.

Meritorious Service Award Presented

to ERNEST M. HARTMANN

JOURNAL OF THE A. S. S. B. T. 88

Mr. Johnson has been a member of the Society since 1952. He has served one Bierinium on the Board of Directors, one term on the Nominating Committee, and has authored or coauthored ten papers published in the ASSBT Journal. He was born in Longmont, Colorado and later moved to Idaho with his parents. He graduated from the University of Idaho with a Bachelor of Science degree in Chemistry. He started with the beet sugar industry in 1939 when he became a bench chemist for the Amalgamated Sugar Company. He was prom­oted to Assistant Chemist in 1941, became Chief Chemist in 1947, Manager of the Research Laboratory in 1958, and was appointed to his present position of General Chemist and Manager of Quality Assur­ance in 1968. He has served as a subject referee on the United States National Committee of the International Committee of Uniform Methods for Sugar Analysis and as an associate referee on ICUMSA. He has been an instructor at the Beet Sugar Institute for four years, lecturing on sugar quality and extraction. He maintains active mem­bership in several technical societies including the Society of Soft Drink Technologists, American Society of Quality Control, and American Chemical Society.

Meritorious Service Award Presented

to JULIAN R. JOHNSON

8 9 VOL. 19, No. 1, MARCH 1976

Mr. Hall has been a m e m b e r of the society since 1956. He has s e r v e d t h r e e b e i n n i a as a d i r e c t o r , o n e b i e n n i u m each on the a w a r d s c o m m i t t e e , n o m i n a t i n g c o m m i t t e e , a n d p u b l i c a t i o n s commi t t ee , a n d as c h a i r m a n of the a g r o n o m y section. He joined t h e b e e t s u g a r i n d u s t r y i n 1944 a s a s s i s t a n t a g r i c u l t u r a l r e ­search s u p e r i n t e n d e n t in t he seed division of the British Co lum­bia S u g a r R e f i n i n g C o m p a n y L i m i t e d , a t V a n c o u v e r , B . C . C a n a d a . Be tween 1947 a n d 1953 he was on the canes ide of his c o m p a n y ' s o p e r a t i o n , r e t u r n i n g to the beet seed research o p e r a ­tion in Alber ta unt i l 1955 when he was t r a n s f e r r e d to the Mani­t o b a S u g a r C o m p a n y a s a g r i c u l t u r a l s u p e r i n t e n d e n t . A f t e r s e r v i n g in this capac i ty for f o u r t e e n yea r s , he b e c a m e g e n e r a l a g r i c u l t u r i s t for t h e bee t s u g a r d iv i s ion o f t h e c o m p a n y wi th o v e r a l l r e s p o n s i b i l i t y fo r t h e c o m p a n y ' s a g r i c u l t u r a l o p e r a ­t ions. He was t r a n s f e r r e d back to the Mani toba S u g a r C o m p a n y i n S e p t e m b e r o f 1 9 7 5 a s a s s i s t a n t g e n e r a l m a n a g e r a n d i s s c h e d u l e d t o b e c o m e g e n e r a l m a n a g e r o f t h e c o m p a n y a s o f Apr i l 1976. Mr . Hal l is a na t ive C a n a d i a n , b o r n in Essex, O n ­t a r i o . H e g r a d u a t e d wi th a B S d e g r e e i n a g r i c u l t u r e f r o m O n t a r i o A g r i c u l t u r a l Co l l ege a n d e a r n e d t h e M S d e g r e e f rom t h e Un ive r s i ty of A lbe r t a in E d m o n t o n . He has b e e n act ive in t h e A l b e r t a a n d M a n i t o b a In s t i t u t e s o f Agro log i s t s , t h e W i n n i ­p e g C h a m b e r o f C o m m e r c e , t h e C a n a d i a n F o o d M a n u f a c ­tu r ing Associat ion, and in his c h u r c h .

Mer i to r ious Service A w a r d P r e s e n t e d

to J O H N WILLIAM H A L L

JOURNAL OF THE A. S. S. B. T. 90