I~r (Sda~r m elonge~r (Musa, - ias

LITTLE LEAF--A TRANSMISSIBLE DISEASE OF BRINJAL

B'~ ~ K. M. THoN,~s, B.A., !V[.Sc., D.I.C. 3.NI)

C. S. KI<ISlt~ASWAMI, B.A., B.Sc.AG. (F roto the A TricuZ~~rc~�91 12~.~se(~rcA I~~stittcte, Coim�91

Yteceived 3![ay 30, 1999

(Communicated by R~o B~h~dur G. N. Rang,~swami &yyangm', L.~.S., I~.N.I.)

I~r TI<I~ briilj al of egg p lant (Sda~r m elonge~r is an impor tant vegetable erop i n South India , its importance perhaps, being second only to t ha t of the plantain (Musa, spp.). I t i s grown all over the Presidency as an irrigated crop, either alone oi- mixed with other vegetables and often asa subsŸ crop in betel gardens. Asa pure crop it is grown in two seasons, one trans-

p]anted in 7uly-August and the other transplanted in December-Januaryo There ate many local varieties which vary considerab]y in size, shape,

colmar and flavour. ]Being a vegetable fancied by all classes of people, ir commands a good market and a good crop will fetch in normal years a return

of not less than Rs. 300 per acre. The crop is subject to the attack of a

number of insect pests and fungus diseases, but so far, no virus disease has been recordecl in South India. In recent years a disease of obscure o¡ resulting in a gradual diminution in the size of the leaves and sterility of

plants has been causing considerable damage to the crop Ÿ a number of places in the presidency, and this paper describes the disease and gives an

account of the experiments carried out at Coimbatore in connection with lis

investigation. Histo~y

The disease was ¡ observed in the Central ]Farm, Coimbatore (Thomas) in 1937 when the invest~gation was ¡ started. Subsequently reports of the disease have been received at the Mycological Section from varions parts of the presidency. In 1938 the disease was observed in a virulent forro at ~ilampur, a village near Coimbatore, causing damage to an extent of nearly 500/o of the crop in the ¡ The disease would appear to be of virus origin. Savulescu (1934) mentions a virus disease of brin]al in Rumania, which causes mottling of foliage and dwar¡ but the disease is apparently entirely different from the one described in this paloer.

201 B7

202 K. M. Thomas and C. S. Krishnaswami

Smith (1937) does not ment ion the disease in the list of virus diseases at tacking solanaeeous plants. Uppai (1929) ment ions a mosaic disease of chillies which causes reduction of 1caves a n d a similar disease of c5illies has been notieed by Park (1934) in Ceylon. Uppal ' s disease however would appear to be sap transmissible, while the Coimbatore disease is not. Coleman's (1917) photographs of Dat.z~~'a stra#~zo~ai~~4,z indieate the possibili ty of a similar disease having been present in South Ind ia at the time. But ir is believed tha t no record of the disease as sueh, of a descript ion of the disease has been made before.*

Etio�91 i~racroseopic and microscopic examinat ion of a large number of affected

plants did not reveal the presence of any cons tan t ly associated inseet, iungus of bacter ium tha t might be held to be the eausat ive organism of the disease. The absence of any living visible organism, was suggestive of a virus being the cause of the disease.

Sympto~r of the Disease The disease has been notieed on br inja l and Do~t~,ra fast,uosa in nature.

Bri~jal.--In brinjaI the most character is t ic symptom is t he reduetion in the size of the 1caves. As the disease progresses the new leaves produced become smaller and smaller with the result t h a t in the course of a month the leaves ate very considerably reduced. The average size of a full grown leal of a two-month old hea l thy p lan t is 10 cm. • 16 cm. and the maximum size of ful ly developed leaves of infected plants is 2 cm. • 5 cm. (Plate V, Fig. 6). Both the petiole and the lamina ate involved in the reduetion, the leaves beeoming almost sessile. There is also considerable modification in the texture of the 1caves. I n hea l thy p lan ts the leal is thick, leathery, hirsute, and dark green in colour. I n diseased p lan ts the leal becomes thin, soft, glabrous, and pale green in colour. I n t h o r n y vadet ies , the thorns in diseased plants tend to get a t t enua ted and in some eases entirely disappear owing to the disease.

Another characteristic symptom is the s tŸ of growth of axil lary buds ineluding the la tent buds, aecompanied by the shortening of internodes of the branches. In eourse of t ime, the suppressed branches wi th numerous reduced leaves get erowded a t the axils and the p tan t presents a charaeter- istie bushy appearance (Plate V, ~'ig. 5). At this stage the appearanee of the p lan t is so entirely ehanged t h a t i t is dif¡ to recognise the originai br inja l lolant.

* Dr . K . l~I. S m i t h i n a l e t t e r t o t h e s e n i o r ~ u t h o r be ] i eves t h i s to be so a n d has suggested th~t the virus be termed Dat~tra Virus 2.

ZiL/�91 Lea/--A Tra~zsmissiMe Disease o/ ]3rifzz)! 203

The third characteristic of the disease is the modification in the floral par t s (phyllody) (Plate V, Fig. 7). In many affected plants there is no t race of any floral parts being present, bnt whenever found these undergo teratological modifications, the corolla, andrcecium and gyncecium turning completely green (virescent). I n cases where the disease makes its appearance af ter the ¡ ate normally formed, the flowers are shed and no fruits ate set. In very rare cases one of two fruits may develop normally. As a rnle however, affected plants ate sterile and do not bear fruit s t all. The li t t le-leaf affected plants ate therefore absolutely worthless to the cultivator. The disease affects the plants in all stages of growth, viz., from the seedling stage till the period of matur i ty .

Dature fastuosa (Purple var ie ty) . - -The disease oceurs on this host in nature . The symptoms ate similar to those deseribed in brinjal, namely, reduct ion in the size of leaves, shortening of internodes, crowding and s t imulat ion of axillary branehes (Plate VI, Figs. 5 and 9). Phyllody is some- t imes noticed but flowers ate often normaland viable seeds ate produced.

Datura fastuosa (White var ie ty ) . - - In the white variety also the disease occurs in nature manifesting similar symptoms but phyllody of ¡ parts is common, and viable seeds ate seldom formed. The erowding of leaves in the axils is very noticeable (Plate VI, Fig. 10).

Tomato.--The disease has not so lar been observed on this plant in nature , but has been induced by grafting. The reduetion in the size of leaves, st imulation of axillary buds and phyllody ate characteristic sym- p toms. Fruits when formed get mmnmified. No viable seeds ate formed. The petioles and young shoots assume a purplish tinge (Plate VI, Figs. 5 and 7).

Tobacco.--The disease has not been observed in nature on tobaceo but has been suecessfully indueed from brinial to tobaceo by grafting (Plate VI, ta'ig. 11). The changes brought about by the disease in this host are very marked. The affeeted plants show all the eharacteristic modifications of virescence, reduction in the size of leaves and stinmlation and crowding of axil lary buds as in the case of brinjal, tomato and datura.

VarietaZ Susceptibility So lar as our present experience goes, all South Indian varieties of brinjal

appear to be susceptible to the disease. I r was not possible to distinguish va¡ of brinjal by morphological eharacteŸ as genetically loure types were seldom found. In a preliminary experiment designed to test the var ie ta l snseeptibility of brinjal to the disease, 28 samples of seed from one source labelled as separate varieties and 8 samples from a firm of relouted seedsmen, were sown in pots, and the plants so raised were exposed to natural

B7a X~

204 K. M. Thomas and C. S. Knshnaswaml

infection. Plants which escaped infect ion were fur ther artificially infected. The results (TabIe I) showed t h a t all t he var iet ies t es ted were susceptible to a greater of less degree.

TABLE I

S~~sceŸ of va~'ie~ies of Solanum melongena to infectio~~

Variety Number of pIa, nts

t, ested

Numbcr showing l i t t!e

lea, f

Central Farm 8

~~ 9

,, 10

. Ii

,, 13

~, 14

~, 16

,~ 17

,, 18

,, 19

,, 20

,, 21

,, 22

,, 23

,, 24

~, 25

. 27

,, 28

. 31

:, 32

7 e~ch

7~

2

3

1

2

3

1

2

3

2

2

2

2

2

5

i

3

4

2

3

2

Litfle Lea/ A TransmissiMe Disease o f Brin~al

TABL~ I--(Contd.)

205

V~riety

Cent, r~d Farm 33

~, 34 �9 o

35* . .

T.C.R.

S. 235

S. 237 L.W.

S. 238

S. 239

S. 240

S. 24.1

S. 242

S. 245

l~umber of plants

~ested

20 ea, eh

Nurnber show- ~ng little

]eaf

3

2

0

3

3

3

2

2

3

3

4

3

* Proved to be susceptible by graf~[ng.

Transmission S~udies Material and Methods.--

Original source of virus. Two af/ected p lan ts collected from the Central Fa rm, Coimbatore, formed the original source of the virus.

Plants.--In a set of p re l imina ry exper iments the p lan ts used were seedlings raised from seed obta ined from a previous erop, which was not dŸ The p lan ts were kep t exposed and no a t t e m p t was made to keep t hem under insect-proof condis Bus in la ter tr ials , the seed was t rea ted wi th ceresan, and sown in au toc laved soil in seed pans which were enclosed in musl in nets to p reven t the en t ry of insects (Plate VI, Fig. 4) and th roughou t the period of g rowth all possible precaut ions were t aken to grow the seedlings under insect-proof condit ions.

Inoculum.--Virus extraer was obta ined by crushing the leaves and tender shoots of agec ted p lan t s in a steri l ised agate mor ta r and expressing


the juice through folds of steri l ised muslin. Hohnes ' (1929) me thod of swabbing the surf~ce of the leal wi th the virus ex t rac t mixed wi th earborundum powder and Sein's (1930) p in-pr iek me thod were adopted for inoculation.

Gra/ t ing . - -This was done by the usual ir tarching mett lod and the stock and scion were t ied with raffia. After the lapse of a few days the s tem of the scion was severed jus t below the graft .

Budding.--This was done by the usual me thod of making a T-shaped cut in the bark of the stock and inser t ing a scion bud wi th a pieee of wedge- sllaped barl,: a t tached and ty ing up wi th raffiai Budding was successful only in a few cases and was given up for la ter exper iments .

fnsect lra~smissio~,.--The seedlings raised were t r ansp l an t ed after 28 days in ear thenware pots ¡ wi th t r ea t ed soil* and immedia te ly enclosed in glass lamp chimneys covered wi th mus l in tops. The insects were either t ransferred direct ly from a diseased p lant , of were enclosed in a glass tube and red on a diseased p lan t f o r a period of not less t han 24 hours prior to transfer. Aphids and t ingids were t ransfer red by means of a sterile camel hair-brush, t ak ing care to see t h a t the insects were not injured. No precaut ion was t aken not to touch the leal wi th the brush, as i t was proved by sap inocula t ion exper iments t h a t the disease was not sap transmissible.

I n the case of jassids, the insects previous ly fed on diseased p lants were i ransfer red to musl in- topped lamp chimlxeys which were subsequent ly placed over the hea l thy plants . I t was found t h a t sooner of la ter the insects set t led down on the p lan t to feed. Six days af ter the t ransfer , t he insects were ki•led by fumigat ing the p lan ts wi th nicot ine fumes of spraying them wi th a solut ion of nicotine sulphate. Care was t a k e n to see t h a t only one kincl of insect was in t roduced at a t ime and in any series where ah unknown insect was found inadve r t en t l y inŸ the series was rejected. As soon as the first symptoms of the disease were not iced the chimneys were removed and the p lan ts were al lowed to grow, under normal conditions. Consider- able difficulty was experienced for wan t of ah inseet-proof gIass-house but th is was pa r tŸ overcome by t ransfer r ing t he exper imenta l plants , to the ve randah of the labora tory in the ma in bni ld ing which is 30 feet h igh from ground leve1 and where owing to the absence of othe~ vegeta t ion nearby, in fes ta t ion of insects other t h a n those in t rodueed was negligible. The controls remaŸ heMthy.

* The soil usecl was treated with boiling water pourecl twice over lbo k¡ aI1 insecSs,

Litf[e Leaf--A Tram~nissiMe Disease of Brb~/al 207

The number of plants used in each series of experiments throughout was not less than five of each kind unless otherwise mentioned. And each series was repeated thrice, so that the total number of plants used was not less than ¡ in any series.

ExJ)eriments and Results

Sap inoculation.--Inoculation done as per the method described supra on the following host plants gave negative results : - -

Solanum melongena, Dati~ra fastuosa (purple and white), tomato, tobacco and Nicotiana glutinosa.

The experiment was repeated four times dufing different seasons of the year, anct no case of t~ansmission was noticed in any of the series.

Grafti~g.--It was found that the disease was easily t ransmit ted from brinjal to brin]al by means of grafting healthy stocks with atiected scions. In the prel iminary experiment in 1937 out of 23 plants grown in the pot- culture house four were grafted with diseased and 4 with heal thy scions and 15 plants were left undisturbed. The four plants grafted with diseased seions took infection and developed symptoms of disease within 28 days, while the others remained free. Since then over 90 grafting transfers have been effected in the pot culture house at Coimbatore.

7~sect transmission.--Attempts were made to see if the following

sucking insects found on brin~al in Coimbatore were vectors :

1. Aphis rumicis Linn. 2. Aphis malvoides Das.

3. Al)Als gossypii (Olor.)

4. Empoasca devastens Dis.

5. Eutettix phycitis Dis.

6. Thrips sp. (unidentified). 7. Urentius echinus Disk.

8. .Phenococcus insoIitus Gr.

Transmission experiments with the aphids and tingids gave negative

Iesults repeatedly.


T~BLE II

ResuI~s of Insect Tmnsmission Experiments

S=,ries

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

Sour('e of

virus

Brinjal

Tom~to

Trans- f~rred

to

Brinjal

Name of the inseet

Aphis ru,micis

Aphis mah:oides

Aphis gossypii

Urcntius eddn..u,s

E~~~2oasca devaste, ns

Eutcttix phycitis

Number of plants

used

6*

6*

6*

6

6

~7

do.

do.

do.

do.

Thri~s sp.

6

6

6

3

5*

Tom~to

Chillies

D atura

S. xantho- ca'rpu m

Brinjul

Tom~to

E mpoasca devasfens

Euteftix phycitis

do.

do.

do.

Thrips sp.

do.

Phe,nococcus insolilus

3

8

4

4

6

3

3

3

Number of p lants infected

0

0

0

i O

1

2

3

3

2

0

0

0

0

0

3

0

0

0

* Repeated four times.

The results show t h a t the two jassids--EmŸ devaste~r and Eutettix phycit is~could t ransfer the disease from br in ja l to br in ja l . Of these t he

Zittle Zea,/--.dl TmmmissiMe Disease ofl Brin]~t 209

number of successfuI t ransfers effeetect by Eutettix phycitis was greater than those effecxed by Empoasca dewstens. Both the jassids ate of common occurrence in the br in ja l fields in Coimbatore, and possibly ate chiefly responsible for the spread of the disease in the fiel&

Host Range

The disease has been successfully t ransfer red from brinjal to brinjal (cult ivated and wild) tomato , trilobatum by means of grafting. in Tables I I I nd IV.

tobacco Datura fastuosa and Solanum The resulls of dlese experiments are given

TABL]~ III

Results of Grafting Ir Scions o~ Different Hosts

Souree of virus

Brinjul

TomMo

D~tura

Brin ja,1

(purple)

(white)

I tost pl~nt ~1etllod

1R, esult

Number of heMthv 1 planta" [

used t

Number of pl~nt, s

iafected

Brin ja]

,, (wild)

Datura (purple)

Tomato

BrinjM

Tom~to

Tobacco

Sa~ntalam a~,bmn

Solanum trilobatu~

Gr,%fting 90 90

7 6

6 5

15 13

3 3

5 3

5 2

5 nil

5 4

2 nil

l l


TABI,~; IV

Period required for developme~~t of sympto.ms

N~ture of infeetion 1Kethod of tra, ns- mission

Time t,M~en for symptoms

to ~ppear

1-r to brinjal

~ d a r , u v a

Tomato to ,,

BrinjM to tobaeco

Insect

Grafting

2,1 to 45 days

21 to 30 ,,

,,

15 to oo

1 6 to 20 ,,

4 0 ,,

Seed Tmnsmission

Ah aŸ was made to see whether the disease is transmissible through seed. Two lots of seed collected from partially diseased brinjal and

Datura fastuos~ plants were sown under insect-proof conditions. No disease was noticed in the seedlings. Ir would appear therefore that the disease is not seed transmissible.

Control

Destruction of all solanaeeous weeds from gardens and prompt removal of affected plants would appear to be the only possible means of keeping the disease in check until resistant varieties are found. In a field where the weeds were completely eradicated and the diseased plants rogued out tlle subsequent incidence was reported to be markedl7 less than ilt the other fields in the same locality.

Summary

A transmissible disease of Solanum melongena has been found to cause considerable damage to the crop in m a n y parts of the iV2adras Presidency. The general nature of the symptoms together with the absence of a visible associated organista was suggestive of a virus being the cause of the disease. Owing to the complete suppression of the productive phase in the affected plants and the high percentage of incidence the loss is very great. The disease is found to be transmissible to Datura fastuoso, tomato, tobaeco and wild brinjal, S. xanthocarŸ and S. trilobatum.

Litl/e Lea/ .,A Tmnsmissible Disegse a/Brilz/M 211

The disease is not transnlissible by sap inoculation but is easily transmitted by means of grafting. Two species of ]assids would appear Ÿ be vectors of the disease.

A cknowledgements

The authors ate greatly indebted to :Dr. K. lVr. Smith, :v.R.s., for examining preserved material and photographs of the disease and to Mr. 5f. C. Cherian, Entomologist to the Government of Madras, for identi- fying the insects mentioned in this paper.

C£ L. C.

Holmes, F. O.

Park, M.

Savulescu, T.

Sein, F.

Smith, K. M.

Thomas, K, NI.

Uppal, B. N.

REFEI~EiNCES

�9 . Depar tment of Agriculture, Mysore State, Mycological Series BulIet fn _Aro. 3, 1917, Plate 4 .

. . .Botanical (iazz�91 1929, 78, 56-,33.

. . Admin is t ra t ion I~elgort, Director of Agrfmdture, Ceylon, 193~-35, D[124~-D/131.

. . In t . Cer. Agron. al. l~vmanie4 1934.

�9 . JournaI, Department of Agric�91 l~orto Rico, 1930, 14, 49-68.

. . A Text-Booir of P lan t V i rus Dfseases, 1937, 560-97.

�9 Admin i s t ra t ion Report of G'overnment Mycolog~st, Madras, for 1937-38, 157.

. . International B~tlletfn of Plant 2rotect,�91 1929, 3, 99.

DESCRIPTION OF PLA,TES

PI~~TE V

]?IG. 1 . - -~iew of a brinjal fiš in ~ village near Coin~b,%#,ore, showing large nulnber o~ affected plants.

FIel. 2.--I~Iealthy and natural ly infected brinjal plants of the same age.

Fin. 3.--~k heal thy brinial plant,

Fin. 4 .--Brinjal plant showing symptoms of d/sease induced by grafting.

Fin. 5 . - -Same plant showing a&vaaced stage of disease.

FIG. 6.--Terminal shoot of a diseased plant showing the reduction in the size of leaves. Leaves fr0m the heal thy p lant of the same age on the right.

FiGs. 7, 8 and 9.--Modi¡ of floral parts brought about by the disease in brin]M. I~[ea/thy flower on the left in Fig. 7.

FzG. 10.--Modific~tioa of floral parts in Datura fastuosa.

FIG. l l.--lViummified fruit of infected tomato plant showing characteristic splitting.

FrG. 12.--Modification of floral parts in tobacco and tomato : - - Top : Tobacco flowers heMthy (left) and infected (right). Bottom : Tomato flowers infected (left) and heMthy (right).


PLATE VIl

FIG. t . - -A b.':injal se~dting (leff,) showing symptoms of disease tra,nsfem'ed by the insect E~detti,v phycitis fed on diseased shoots. Contzrol--he~lt, hy pkmt~ on the right,.

FIa. 2.--Same pI~nt two months l:~t, er (Control not in the pic~ure).

Fin. 3.--(1) BrinjM seedling 28 days old (cm~tro]). (2) . . . . . . . . infected by Eutettix phycitis. (3) . . . . 2 months old infected by Eu,tettix phycitis.

Fiel. t . View of [nsecs c~ges in which seedlings were r~ised for t,h:~ exper iments .

Fin. 5.--Showing disaased plants (lefb t,o right) of brinjM, 5ornato, Datura Jhstuosa (purple) and Dahtra fa, stuosa (white).

Fin. 6.--Solanum melonge~~a (wild) showlng the disease induced by grMting.

Fin. 7.--Sho~x2ng healthy (left) aad disemsed (right) tomato pl-mts (v~u'. GohIen queen). Disease transmitted from brinjal b y grafting.

Fin. 8.--Diseasecl tomato plaat (var. DwLu'f giant).

Fin. 9.--Dat~tra fastuosa purple var ie ty showing he~l thy p lant (left) ah(! in:fected plant (right).

FI~. lO.---Datura fastuosa (whit, e) heal thy (extreme left), showing symptoms in etuqy stage (middle) and showing symptoms ir~ adva,need stage (extreme right).

F~as. 11 and 12.--Tobacco pl~nts (variety : Harrison special), showing dise~~se induced by grafting.

IC M . Thomas a~ld C. �91 t(.rish~zaswmui

Proc. ~nd. A cad. Sci., t3, roL X, Pl. V

k~ o

A". J'Ÿ ]'hom.as alid C. S. IGrishnas.zt,ami

_l,'roc. lJid. ,.tcad. Sci,, IL :.o/, .V, t 'L 1.'i

�9 ~,~~~,,r ~~;~~~ =~, ~ �9 ~i~ '~ ~~ ~,,~ ..... ~ ~ ~ ~ ' ~ ~ ' ~ i~~

6

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I~r (Sda~r m elonge~r (Musa, - ias