116 Agricultural Section

...:;.

large number of seedlings than a larger increase of a smaller number. It dependsto a great extent on how much confidence can be placed in one's appraisal of theoriginal single stool. Since neither the quantity of cane available at that stage,nor time and funds would permit settling all the questions that must be answeredbefore a cane can be discarded, it has seemed preferable to us to make an initiallysmall increase ofa fairly liberal number of selections, ,with more drastic weeding­out by both pathologists and agronomists later on.' And :;ts mentioned, all of theseed may 'be saved from the original stool of a seedling that appears to be out-standing from any standpoint. '

REFERENCES

[1] Abbott, E. V. 1949. Comparison of methods for artificially inoculating sugar-cane seedlings:with the mosaic virus. Phytopath. 39, 668-669.

[2] and Summers, Eaton M. 1942. Disease testing and initial seedling selection.work at the Houma Station during 1940 and 1941. Sug. Bull. 20, 137-141.

[3] Sartoris, G. B. 1943-1947. New kinds of sugar cane. Yearbook U.S. Dept. Agric., 353-356.

DISCUSSION

In reply to Dr. Dodds, Dr. Brandes said that in the U.S. they used paper pots mainly for'raising seedlings. Dr. Dodds stated that in South Africa, clay pots were the most economicalway to raise seedlings. Dr. Li said that in Taiwan they.used concrete slabs with about three­quarters of an inch of soil on top to raise seedlings.

Mr. Buzacott drew the attention of the meeting to the author's statement that robusturn.blood caused lodging. He stated that in Queensland the reverse occurs, robustum. canes beingvery erect. For this reason 28 N.G. 251 was now used extensively in Queensland. Dr. Brandes.stated that material should not be condemned simply because of its habits in anyone locality;the difference in habit of robustum. canes in Queensland and Louisiana would' probably be dueto differences in latitude.

In reply to Mr. Hughes, Dr. Brandes said that the waist-like shape of the internodes of'Queenslandl'obustum canes had not been observed in Louisiana and was probably caused by theenvironment.

In the absence of the authors the following paper was also presented byDr. Brandes, •

Paper

EVIDENCE OF INHERITANCE OF RESISTANCE TO FREEZE INJURY INSUGAR-CANE SEEDLINGS PRODUCED AT 'CANAL POINT, FLORIDA

GEORGE ARCENEAUX, ROBERT E. COLEMAN and LEO P. HEBERT

Division of Sugar Plant Investigations, United States Department of .Aqriculturel

INTRODUCTION

Detriment to sugar cane resulting from low temperatures is the principaldisadvantage incurred in the cultivation of this crop under temperate zone.conditions. The damage ranges in degree from arrested or greatly retarded growthat .cool temperatures to outright killing back of the plants under severe freezingconditions. It has been pointed out by Brandes et al. [2] that from one third toone half of the world's output of sugar from cane is produced in the temperatezone, therefore the development of a race of sugar cane capable of more satisfactorilytolerating low temperatu~es is of widespread interest and importance. '

The breeding of sugar-cane varieties resistant to cold injury has been oneof the major objectives of the work of the United States Department of Agriculture

. at Canal Point, Florida. As shown by the literature [2, 3, 4] thecollectirig 'ofp~rent material as planned by Dr. E. W.Brandes and, for the most part, carriedout under his direction, covered most of the world's regions where wild andcultivated forms of sugar cane occur, with special emphasis on the search for for~sindigenous to the temperate zone.

Seedlings produced at Canal Point during the past 25 years have beensystematically tested for growth qualities, sugar content,millingqualities and

.other characters of economic importance. The best of these have been releasedfor commercial culture and now account for the great bulk of the sugar caneproduced in continental United States.

Sugar-cane varieties which eventually find economic utilization constitutea very minor fraction of original progeny groups. Forpractical reasons the vastmajority of other seedlings must be promptly discarded to make room for thenew groups produced annually, but it has been the policy at the Houma Station tokeep a permanent collection of all seedlings which have beeri found sufficientlypromising to be placed in outfield agronomic tests. This ever-growing referencecollection, now increasing at the rate of 8 to 9 per year, represents the" cream ';of the various progenies tested. Varieties in this collection are replanted fromyear to year and are thus always .available for miscellaneous observations incomparison with other seedlings in. the various stages of agronomic tests. Inthis connection special attention is given to results of uncontrollable factors suchas wind damage and freeze injury.

Aside from the fact that field temperatures cannot be manipulated to meetexperimental requirements the measurement of resistance to freeze injury in sugarcane presents other complicating difficulties. The term "resistance to freezeinjury" has been interpreted to mean :

(1) Resistance of the plant tissue to observable injury such as killing of foliage,destruction of buds and discolouration of stem tissue.

(2) Resistance to fermentative disintegration following freeze injury. Somevarieties such as C.P. 29/120 have been reported as deteriorating lessrapidly than others following a damaging freeze [7].

(3) Resistance to stubble failure associated with the prolonged standing offrozen cane on the stump [1J.

This study relates essentially to the resistance of foliage to freeze injury.At the present stage, varietal differences of a relatively small order are involved,therefore a satisfactory separation of the various individual seedlings intosusceptibility groups can be made only at temperatures within a fairly narrowrange. Above such a range no damage whatever will be observed and below itall varieties will be severely killed back.

.FREEZE INJURY TO MATURE SUGAR CANEMost of the reported observations on injury to sugar-cane tissue as a result

of freezing temperatures have been made on plants in relatively advanced stagesof growth. Our information shows that under such conditions, results obtainedmay be greatly influenced by secondary factors.

G. Arceneaux, R. E. Coleman and L. P. Herbert 117

118 Agricultural Section

Records of temperatures taken at different elevations in fields of sugar caneshow that, as a rule, on a clear, cold night the lowest temperatures occur at aboutpane-top elevation as a result, no doubt, of loss of heat due to radiation from theexposed surfaces. The higher temperatures recorded between the ground surfaceand cane-top levels reveal the protective value of the foliage cover by reason ofits interference with radiation and convectional loss of heat from the soil. Itseffectiveness will obviously depend on how completely the foliage forms a canopyover the cane field" hence the common observation that sugar cane becomes moresusceptible to cold injury after lodging. It might be mentioned also that certainvarieties with recumbent leaves, notably Co. 290, form a much more effectivefoliage blanket over the field than do varieties with more erect leaves. vVe havefound that such a varietal character can be of considerable importance undermoderately cold conditions, but as might be expected, the protective mechanismbreaks down .under conditions of a severe freeze .:

When night-time temperatures are depressed to the point of a light freezeunder conditions of intensive radiation, the first damage of serious consequenceto sugar cane ordinarily consists of the killing of terminal buds. Since the elevationof terminal buds may vary greatly from stalk to stalk in the same stool it may beassumed that the temperature to which they are exposed will vary accordingly.It has been our observation that, as a rule, under such conditions, all varietiesof cane will suffer some terminal bud injury while some of the terminal buds ofalmost every variety will escape with little or no injury. Occasionally importantvarietal differences as to percentage of terminal bud mortality have been observedbut in most cases evidence of varietal resistance to' cold-induced injury as such

could not be clearly established.

FREEZE INJURY TO SUGAR CANE IN EARLY STAGES OF GROWTH.Mild weather conditions prevailing in southern Louisiana during December,

1948, and January, 1949, permitted extensive development of new growth oncane stubble. In most cases, shoots from stubble of cane harvested during latefall or early winter had attained a height of 12 to 18 inches. A cold 'wave over

.the period January 31-February 2, inclusive, brought temperatures to freezinglevels throughout the Louisiana sugar-cane belt. At the Houma Station the coldspell was accompanied by occasional flurries of snow and sleet, and a drizzlingrain which froze on exposed plants as it fell. Daily minima recorded in the standardshelter ranged from 25 ° to 29° F. Recording thermometers at an elevation of3t feet in the field which became coated with ice registered the following

temperatures:

Temperature (F.)

Date

January 31February 1February 2

Minimum

29.5°29.5°29.0°

I Maximum

33.5°42.0°63.0°

G. Arceneaux, R. E. Coleman and L. P. Herbert

- --------.--.-~~_,__-----,

119

Failure of outside temperatures to reach: the low levels recorded in the standardshelter was no doubt due to the buffering effect of the freezing rain.

It is believed that temperature conditions as reflected in the above recordsapproximated those to which growing plants of sugar cane were 'subjected, butit is possible that the latter enjoyed a slight advantage by reason of being somewhatcloser to the ground surface. No temperature records are available from thatexact level.

Field observations made after the freeze revealed a wide range in degree ofinjury suffered by different cane' seedlings: SOme had been killed back to theground surface while othershad suffered only minor foliage injury. Thus the freezesituation presented ideal- conditions for a separation of the various seedlings intodifferent categories as to cold tolerance. '

During the period February 7-8, inclusive, 592 Canal Point seedlings inagronomic plantings at the Houma Station were examined for freeze injury. Thisgroup included 13 released varieties, 101 "superior" but unreleased seedlingsin the permanent reference collection previously referred to, and 478 other seedlingsin various stages of agronomic tests. The'latter included C. P. seedlings of '4Gand '47 groups and agronomic selections of the '43, '44 and '45 groups.

In appraising the extent of freeze injury, an index value of 1 was assigned toseedlings showing about 10 per cent. of the foliage killed; an index value of '2,

" to seedlings showing about 20 per cent. of the foliage killed, and accordinglyhigher index values 'to seedlings showing more severe damage. Thus an indexvalue of 10 'was assigned in cases where all plants had been killed back to theground surface. In order to reduce to a minimum the subjective element in thesystem of measurement, each seedling was rated by three observers independentlyand the three ratings were averaged for the purpose of this study. On the whole,the index values assigned to any given seedlings by different observers were invery good agreement. The order of differences in apparent freeze injury betweenseedlings in relation to variations in rating due to personal judgment may beestimated by the following results, of an analysis of the variance among the 1776individual ratings:

Degrees ISource of of Sum of

Ivariance freedom squares Mean square F. i --,-~--

Differencesbetweenseedlings 591 6342 10.73 6.39

IRemainder 1184 1991 1.68

Ii

Total 1775 8333 II I

The above analysis indicates that effects of differences in standard of evaluation, between the three observers and other subjective elements of the rating systemwere very small in eom-carison with observable differences between varieties.

120 Agricultural Section

Table 1 gives the distribution as to estimated degree of freeze injury sufferedby seedlings of groups from each of 13 separate crosses and by those of anothergroup derived .from a number of different crosses. Inspection shows that whileseedlings within each of the various groups varied widely as to degree of freezeinjury, the various progeny groups displayed extremely important differences asto average injury and as to the distribution of seedlings among the different degreesof injury. For instance 80.1 per cent. of the seedlings from the cross C. P. 34/120 xC. P. 30/24 fell in injury groups of index 6 or larger while 72.7 per cent. of thosefrom the cross Co. 281 x C. P. 1165 fell in groups of index 5 or smaller. While 25.5per cent. of the seedlings from the Iatter cross were highly resistant to freeze injury

30

25

t- 20zwua:~ 15

10

:>

Figure

/\I \

I \I \

I \

~o. 281 X C.P. 1165 I \ C.P. 34-120 X

• / \ C.P. 30-24

/ \ 'I \

\'\ I \

\ / \\\/ \~ / \

/,........ I \/ ......../ \

..----// ~ \

2 3 4 5 6 7 8 9 10FREEZE INJURY INDEX

I.-Percentage distribution of sugar-cane seedlings in each of two progeny groupsaccording to observed freeze injury.

..

(index values 2-3) only 5.5 per cent. of seedlings from the former oross showed acomparable degree of cold resistance. Figure 1 shows graphically the distributionaccording to freeze injury of seedlings of the two last mentioned progeny groups.

Of the 13 parent varieties shown in Table 1, seven were available for freezeinjury determinations. The mean and extreme values of freeze injury indexassigned to seedlings of each of 13 crosses are compared with the observed degreeof injury suffered by the parent varieties in Table 2.

Results obtained with the four crosses on which information as to coldresistance of both parents is available, reveal the following significant relationships:

(1) The mean value for freeze injury index of seedlings in each progeny grouproughly approximated the mean value of the parents.

(2) Some seedlings in each progeny group were more resistant to freeze injurythan was either of the parents.

•

TABLE 1

FREQUENCY DISTRIBUTION OF SEEDLINGS AS TO DEGREE OF FREEZE INJURY IN GROUPS ACCORDING TO PARENTAGE,

-Mean

Parentage No. of Distribution as to freeze injury index * freezeseedlings

I

~

I

injurystudied 1 2 3. 4 5 6 7 8 9 10 index

06. 281 x U. S. 1694 .. · . 50 1 1 11 12 11 6 5 3. ~ - 4.700. 281 x O. P. 1165 .. · . 55 - 3. 11 14 12 9 2 3. 1 - 4.7O. P. 3.4/120 x O. P. 3.6/211 ·. 25 1 2 1 9 5 1 1 2 3. ~ 5.0P.O.J. 2725 x O. P. 1165 · . 25 - - 2 5 7 6 5 - - - 5.3.P. 3.3-3.0 x O. P. 1165 · . 14 - - 3. 3." 2 3. 1 - 2 - 5.3.00.281 x O. P. 27/108 · . 44 - 3. 4 7 7 9 5 . 7 • 2 - 5.5C. P. 3.4/120 x C. P. 27/108 .. 56 - 5 5 8 10 8 7 ]0 3. - 5.6Co. 281 x C. P. 1161 .. · . 25 - 1 2 4 3. 6 6 2 1 - 5.7C.P. 3.3./229 x C. P. 3.3./224 · . 14 - 1 1 2 3. - 4 1 2 - 5.9Co. 281 x O. P. 27/3.4 · . 12 ' - 1 - 2 2 - 3. 3. 1 - 6.2P. 3.3.-3.0 x C. P. 1161 · . 10 - - - 2 l' 1 1 5 - ~ 6.6C. P. 3.4/120 x C. P., 3.0/24 · . 146 - 2 6 7 14 9 28 48 28 4 7.2P.O.J. 2725 x C. P. 1161 · . 9 - - - - 1 1 1 4 2 - 7.6Other combinations .. · . 107 1 7 10 13. 19 14 15 19 8 1 5.7

-All crosses .. · . 592 3. 26 56 88 97 73. 84 107 53. 5 -5.9-------

* See text for description of weather conditions ami the method employed in measuring degree of freeze injury.

o;J:.,~.

~'".,,--~~

tJ:'JC]

~

'"~~."~."..

t-<

~

~'";;;.

,....~

122 Agricultural Section

TABLE 2c-~~---~----------------_.-.

- -ale I Mean

Freeze injury index ofparents

___~ 1_Cross

Co. 281 x U.S. 1694 . _Co. 281 x C.P. 1166 ..Co ~Rl x C.P. 1161 ..C.P. 34/120 x C.P. 30/24C.P. 34jl20 x C.P. 36/211P.O.J. 2725 x C.P. 1166P. 33/30 x C.P. 1166Co. 281 x C.P. 27/108C.P. 34/120 x C.P. 27/108C.P, 33/229 x C.P. 33/22·1 ..Co. 281 x C.P. 27/34P. 33/30 xC.P. 1161P.O.J. 2726 x C.P. 1161

6.56.56.56.16.1**

6.56.1

*6.5**

3.73.76.:17.0

*3.73.7**

4.6

*6.36.3

5.15.16.46.5

4.74.75.77.25.05.35.3~ ­

\0.0

5.65.96.26.67.6

1.02.02.31.71.02.73.02.02.02.02.23.75.3

8.39.08.7

10.09.07.39.09.29.39.09.08.09.0

* Variety was not available for cold injury observations.

In' the case of each of the nine other crosses, the freeze resisting characteristicsof only one of the parents was determined. Results obtained with the seedlings,in these cases also, tend to c~nfirm the- above generalizations.

•An analysis of results obtained with individual parents adds further supportto the view that freeze resistance in the material under consideration was inheritedin a predictable manner and tended to be transmitted by a parent in proportionto its own pheno~ypic qualities in this regard. In this connection, results obtainedin six crosses involving C.P. 1161 showing a freeze injury index of 6.3, and C. P.1165 showing an index of 3.6, are especially interesting:

Cross Mean freeze injury index of seedlings

Co. 281 x C. P. 1161P. 33/30 x C. P. 1161P.O.J. 2725 x C. P. 11.61

5.76.67.6

Co. 281 x C. P. 1165P. 33/30 x C. P. 1165P.O ..J. 2725 x C. P. 1165

4.75.35.3

Thus, within the groups studied, seedlings obtained from C. P. 1165 crossed withthree different females, showed in each case a greater average degree of resistanceto freeze injury than displayed by seedlings obtained by crossing the same femalevariety with C. P. 1161.

The available information based on progeny studies made so far is notconsidered sufficiently complete to permit an accurate evaluation of genotypiccharacteristics of the various parents with reference to cold resistance, but fromavailable records the latter may be ranked approximately as follows in descendingorder of ability to transmit cold resistance to their offsprings; the number inparenthesis is the freeze injury index of the parent:

G. Arceneaux, R. E. Coleman and L. P. Herbert

Female parentsCo. 281 (6.5)C. P. 34/120 (6.1)P. 33/30 *P.O.J. 2725 *

Male parentsU. S. 1694 (3.7)C. P. 1165 (3.7)C. P. 36/211 *C. P. 27/108 *C. P. 27/34*C.P. 1161 (6.3)C. P. 30/24(7.0)

* Val:iety wasnot available for cold injury determinations.

123

It will be noted that wherever the information is available there is reasonablygood agreement between ability to transmit cold resistance and correspondingphenotypic qualities.

The following is a list of the C. P. seedlings showing the highest degree of coldresistance in studies previously described:

Group I. Freeze injury rating 1 to 1.49 :33/409 46/115 47/191

47/11747/12747/14147/14647/16147/194

Freezeinjury rating 1.50 to 2.49 :

45/13 46/13146/8 46/14046/1846/16946/19 47/846/36 47/1346/99 47/2546/116 . 47/104

Group II.

80728/1132/20634/5343/3344/53

Group III. Freeze injury rating 2.50 to 3.49 :

28/1929/12129/28333/14233/31033/37233/45933/47234/2534/15136/10536/18343/343/43

44/2644/78

·44/10644/13244/15545/845/1945/2845/3545/9245/12345/14645/15546/7

46/1546/4446/4746/4946/11946/14446/14846/17346/17446/19146/19247/1947/2247/30

47/3347/5247/5347/5947/9847/10947/11147/11347/11647/13347/13647/15547/170

.47/178

The chance of developing a variety combining superior resistance to freeze injurywith other desirable characters could be greatly affected by linkage relationships.It is therefore of interest to know the extent to which cold resistance has beenassociated with other characters of economic importance. !

TABLE 3FREQUEN"CY DISTRIBUTION OF SEEDLINGS AS TO DEGREE OF FREEZE INJURY IN GROUPS ACCORDING TO RELATIVE SUCROSE CONTENT OF CRUSHER

· JUICE -~

, I MeanRelative sucrose content (pol) No. of Distribution as to freeze injury index . I tr~ezeof crusher juice (C.P. 34/120= seedlings

IIDJury

100) studied 1 2 3 4 5 6 7 8 9 10 index

Below 66 · . · . " . 25 - - 1 2 3 4 3 9 3 - 6.8.66-70 · . · . · . 21 - - 1 4 5 - 3 7 1 - 6,271-75 · . · . · . 31 - ~ 4 5 3 2 9 5 3 - 6.176-80 · . · . · . 55 ~ 2 4 9 8 12 4 11 3 2 6.081~85 · . · . · . 82 - 2 6 10 13 10 14 19 8 - 6.286-90 · . · . .. 73 - 5 7 11 7 8 9 12 13 1 6.191~95 · . · . · . 83 ~ 3 11 12 13 8 12 15 9 ........... 5.896-100 · . · . 85 >-=-- 4 11 10 17 14 13 10 5 1

I

5.6101-105 · . · . · . 72 1 6 6 16 15 8 5

I

11 3 1 5.2106-110 · . · . · . 40 1 3 1 8 6 5 7 4 4 - I 5.7

Above 110 · . · . · . l!J 1 - 4 1 5 2 2 3 1 -

I

5.3

Total · . · . · . 586 3 25 56 88 95 . 73 81I

107 53 5 5.9

-

'"""I>:l~

~

~

~~~

.~~-s-.o~

3.85.35.15 ..54.76.0.6.3-

5..2

Meanfreezeinjuryindex

3

8

2

7

116"2112

14

123424

6

16

5

35431

16

4221

4

,9

Distribution as to freeze injury index

~I __ 3

11413

10

112

2-

5

1

TABLE .4FREQUENCY DISTRIBUTION OF SEEDLINGS AS TO DEGREE OF FREEZE INJURY IN GROUPS ACCORDING TO MILI,ING FACTOR

(EXTRACTABLE JUICE CONTENT)~

__ 0.-~ .

No. ofMilling seedlingsfactor studied 1

94 5 196 11 -98 21 --

100 15 --102 11 -1(l4 11 -106 3 -

Totals .. 77 1

G. Arceneaux, R. E. Coleman and L. P. Herbert 125

Data on comparative juice analyses are available on 586 of the 592 seedlingsincluded in the statistical analysis summarized, in Table 1. .These were dividedinto 11 groups according to the relative percentage of sucrose (pol) in cr~sher

juice and the distribution according to freeze injury index of seedlings in eachBucrose- level group was recorded. Results are presented in Table 3.

It will be, noted that while seedlings in each pol group were rather widelydispersed as to freeze injury index,average group values for freeze injury indextended rather consistently to decrease with an increase in the pol level of the juice.This is a favourable association from the standpoint of practical breeding objectives.

Tests of milling qualities at the Houma Station are made only on seedlingsin relatively advanced stages of agronomic tests. Of the entire number inspectedfor freeze resistance 77 had been tested for milling qualities. These could bedivided into seven groups according to yield of normal juice per ton of cane. Thedistribution of seedlings according to freeze injury index in each of these groupswas recorded. Results are shown in Table' 4.

According to the system followed in measuring varietal milling qualitiesCo. 281 is used as standard; it is represented by the value 100. Varieties of thelowest millability group (94) would yield approximately 6 per cent. less juice,and those in the highest group (106) would yield approximately 6 per cent. morejuice than Co. 281 under comparable c~nditions. For obvious reasons the ex­tractable juice content of a variety bears approximately, an inverse relationship tothe relative level of fibre content.

\

It is seen from the results of the analysis presented in Table 4 that there wasa positive association between degree of freeze injury and yield of juice per ton ofcane. This is another way of saying that resistance to freeze injury was positivelyassociated with percentage of fibre content. It will be noted however that eachmillability group showed a relatively wide range in distribution as to extent offreeze injury. Thus the low extraction groups contained some individuals whichsuffered severe freeze injury, and conversely the high extraction groups containedsome individuals which suffered relatively little injury. This indicates that theobserved association is probably more a matter of genetic linkage than a purelyphysical relationship.

DISCUSSION

The groups of seedlings included in this study consisted of exceedingly smallfractions of whole progenies. This obviously detracts from the value of the data

. as a basis for fundamental genetic analysis. On the other hand it has been shownthat the parents investigated varied greatly as to their ability to transmit qualitiesof freeze resistance to seedlings of superior merit which from a practical standpointis the all-important consideration.

Observations presented and discussed above may be readily explained if weassume that inheritance of resistance to freeze injury in the case under studyis controlled by several factors instead of a single factor. The wide dispersalof individuals as to freeze injury index in the respective progeny groups, and thetypically skewed distribution of the populations as illustrated by Fig. 1,are

126 Agricuuural Section

especially suggestive of multiple factor inheritance [5, 6]. If this be so, it may beassumed that, by systematically selecting parents from the more reeistant.groupsfrom generation to generation, still more resistant .forms of sugar cane could bedeveloped as a result of further segregation of underlying genetic factors. Frominformation at 'present available there is no basis to predict the exact order ofresistance which might ultimately be attained, but it is considered a reasonablepossibility that a race of sugar 'cane of substantially increased resistance to coldinjury can be developed. Observedlinkage relationships between level of sucrosecontent in juice and resistance to freeze injury were positive. The negativeassociation found between extractable juice content and resistance to freezeinjury may tend to complicate the problem of combining these two desirablecharacters, but will probably not present important difficulties.

Although any substantial increase in degree of freeze tolerance would, nodoubt, be reflected to some extent at all ages of the plant, the development offorms of sugar cane capable of toler~ting low temperatures in relatively earlystages of growth appears to be a better theoretical possibility than the developmentof forms which could maintain a corresponding advantage at more advancedstages. With mature cane, the elevated position of the highly vulnerable terminalbuds in the midst of a zone of active radiation and consequently depressedtemperatures presents an extremely important hazard on a clear, cold night.

A few of the sugar-cane seedlings developed so far endured the lowesttemperatures of the 1948-1949 winter with only superficial'injury to shoots, whichhad developed earlier in the season. With commercial varieties of cane capableof similarly tolerating the somewhat lower temperatures which may be normallyexpected, summer plant cane and regrowth from early cut stubble would resumegrowth in the spring at a relatively advanced stage of development. Such canecould be expected to reach commercial stages of maturity at a comparativelyearly date in the succeeding fall, thus possibly permitting a substantial advanceof the beginning date of grinding operations. By obviating the necessity of extend­ing milling operations'into late December or early January such an advance inthe harvest schedule would largely eliminate the freeze hazard to mature caneand at the same time would remove maI~Y of the present difficulties of late-seasonharvest resulting from frequent rains to be expected at that time of the year.n should be mentioned also that preservation of growth developed during winterand pre-winter months would result in an extremely important ecological advantagein the competition of the crop plants against summer weeds. •

The following generalizations summarize results of observations presentedin this report :

1. Extent of damage to individual seedlings ranged from approximately/" 10 per cent. of the foliage killed, to severe destruction of all growth to the

ground surface,

2.. Significantly important average differences as to degree of injury wereobserved between seedling groups of different parentage and such differenceswere closely related to corresponding phenotypic characters of the parentsinvolved.

G. Arceneaux, R. E. Coleman and L. P. Herbert 127

3. Individuals of the same progeny group varied widely as to degree of injurysuffered. In the case of every cross studied there were some seedlingswhich were more resistant than either of the parents.

4. Observed distribution patterns suggest a typical case of multiple-factorinheritance.

REI EH,ENCES

'[1] Arceneaux, G, Hebert, L. P, and Krumbhaar, C. C. 1942 Resulfe of sugarcane varietytests in Louisiana during 1941. Sugar Bull. 20 (18),,149,154.

[2] Brandes, E. W' , Sartoris, G. B. and <1rass1. C. O. 1938. Assembling and evaluating wildforms of sugarcane and closely related plants. Pr-oc, nth Cong 1.S S.C.T. 128-1fl4, illus.

[3J ----' -, ----- 1937. Sugarcane: Its origin and improvement. U.S. Dept.Agr. Year Book H137. 661-623 'illua.

{±] ---0'-- i929. Into primeval Papua by seaplane. Natl. Geogr.Mag. 56, 253-332,illus.

.f5] East, E JH. 1910. A Mendelian interpretation of variation that is apparently continuous.Am. Naturalist. 44. 65-82.

[6] Emmerson, R. A., and East, E. M. 1913. The inheritance of quantitative characters inmaize. Neb_ Agr-, Expt. Sta. Reo. BulL 2.

P] Simon, E. O. 1943. A comparison of C. P. 29/120 and 00. 281. Sugnr Edl. 2"1 (22), H14-196.

DISCUSSION

Dr. Dodds stated that in South Africa,Co.281 was frost resistant and he would cxpect itto be a good parent for colclresistant types.

Dr. Brandes in reply to Mr. Bovell, said he was not sure whether the millability factor,i'eferred to in the paper, was a question of fibre or general millability qualities.

In reply to Mr. Burns .Inr. as to whether there was any relationship between canes ableto resist freeze and canesn.ble to grow during the cold months, Dr. Brandes stated that with'Turkmenistan canes there was a relationship .but not. with other varieties.

Mr. Grimes agreed with the authors' statement that observed linkage relationships betweenlevel of sucrose content in juice and resistance to freeze injury were positive. Instancing a local.example, Mr. Grimes stated that Q.42, derived from Co.2S1, had reasonably early sugar and ameasm-o of resistance to freeze injury.

In reply to Mr. Hughes, Mr. Grimes said that 'temperatures as low as 23°F. had beenTecorded at Bmldaberg, and Mr. 'Baber reported that on one occasion in New South 'Vales atemperature of 26°F.' was experienced for ten hours, causing a severe freeze.

Dr. Brandes, in reply to Mr. Robinson, stated that the durat.ion of the low temperatures. recorded in this experiment would probably be about two hours.

Dr. Dodds said that, the lowest temperatures in Natal sugar lands were in the vicinity of41°F. s.cr.een tempern.tm-o or 33°F. terrestrial temperature.

Mr. Grimes suggested there was a relationship between soil moisture and freeze injury, andquoted an example where, at Bundaberg, a field irrigated six weeks prior- to a frost, 'wasunaffected and gave. a good stand of cane, while adjoining unirrigated fields produced corkycane. .

Dr. Brandes stated that it would be advantageous to have canes tolerant to low temperaturesrather than freeze resistant. ' These canes would be of use in tropical countries where frosts

'are not experienced, but where 'winter tempcrat.uros retard the growth of the cane. Dr. Dodds .•pointed out that such a cane would be usefu] for South African conditions, since at presentwinter temperatures below 70°F. compelled them to grow two-year crops in order to obtainmature cane.

In reply to Mr. Bovell, Dr. Brandes indicated that dry weather and not necessarilydormancy caused by cold weather, was associated with ripening of cane.

Mr. Burns .Inr. stated that .in Hawaii there was a decrease in growth during the wintermonths and this necessiatated growing an IS-2'O-months' crop; in view of harvesting problemsassociated with this crop pract.ioe, it may be necessary for Hawaiian planters to change theirviews and harvest after 12 months.

Mr. Wilaon said that the slowing down of growth during winter was connected more withseasonal growth gradients than with low temperatures,