WORKSHOP ON POST HARVEST LOSSES AND SMALL FARMER STORAGE

NEW C E L H I , 19-24 APRIL , 1982

(Organi sed by the Commonwealth Secretariat in Collaboration with the Ministry of Agriculture, Department of Food, Government of India)

Volume I1

REPORT OF THE WORKSHOP : COUNTRY AND TECHNICAL PAPERS PRESENTED

(Volume I comprises t h e summary of t h e proceedings including the

proposed follow-up action programme.)

rood P r - o d i ~ c t i o n and R ~ r a l Oevelopment Division : Co~ilinonwea I t h Secretariat )

Narl borough House Pall Mall London SW1 I) K

POST HWVEST P R O ~ M E IN ICRISAT~

by

D EkDonald and V K Plehan*

Paper presented a t the Workshop on Post Harvest Losses and Small Fanner Storage for South Asia and ECS Xf~ica , New Delhi, India, 19-24 April 1982. Not to be cited. Shmitted for approval by the ICRISAT Editorial Conmitteel

P r inc ip l Pathologist and Pathologist, Gromdnut Improvement Program, International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patmcheru P 0 502 324, , India

I n t r o d ~ t ion

The basic role of ICRISAT is t o serve the s m l l fanner of the Semi- Arid Tropics (S4T). The four main objectives of the research program are:

1. To serve a s a world centre t o improve the genetic potential for grain yield an3 nutritional quality of sorghum, pearl millet, pigeonpea, chickyea, and groundnut.

2 . To develop fanning systems which w i l l help to increase and s tab i l i se agricultural production through bet ter use of natural and h m resources in the seasonally dry semi-arid tropics.

3. To identify socio-economic and other constraints to agricultural dcvelo#ment in the semi-arid tropics and t o evaluate alternative means oE alleviating them through technological and inst i tut ional changes.

4. To ass i s t national and regional research programs through cooperation and support and t o contribute further by sponsoring conferences, operating international training program, and assis t ing extension ac t iv i t ies .

For the comprehensive nature of these objectives it is clear that p s t harvest problems f a l l within the mandate of ICRISAT. However, many of the important storage problems of SAT crops are already being handled by specialised inst i tutes , and th is , and the pressing nature of the many f ield problems affecting the crops has led t o the present relat ively low priori ty being given t o research on p s t harvest problems.

In t h i s paper brief mention w i l l be made of a storage pest problem tha t has received attention a t ICRISAT, and of a socio-economic investigation of the impact of machine threshing of cereals in an Indian SAT village. Most of the paper w i l l be devoted t o research a t ICRISAT on the problem of aflatoxin contamination of g r o ~ d n u t s , a very serious problem i n a l l parts of the world hhere the crop is grown, and one which has important post harvest and storage components.

Bruchid Infestation of Stored Pigeonpea and Chickpea Seeds

Callosobruchus spp are found a s appreciable infestations of mature pigeonpea pods when the crop is in the f ie ld , but examination of numerous samples of chickpea pods from India and other countries indicates that infestation with these insects is a purely post harvest &enomenon.

In cooperation with ICRISAT scient is ts , Professor E m t K Horber of Kansas State University, USA, has been studying the chemistry involved in the differences i n susceptibility t o bruchids found in pulse seeds. Substantial differences in susceptibility have been found among the germplasm l ines tested.

. - - Several vegetable o i l s have been tested for the protectian of pigeon-

pn and chickpea seeds from bruchid attack and the treatments have been found t.:fectivc. Similar resul ts have been obtained by other workers and the use of o i l s for t h i s purpose i s said to be a long established practice of some farmers i n I i l d i ~ .

,.. . . i I ..:;. 2 i .<;'i>l, ir,!:nct o f bhchine Threshing of Sorghum

i n contrast t o the highly productive irrigated regions, diffusion of i n thc SKI' of India has not been widespread, demand being limited by

s ~ n factors as revenue uncertainty, low Nages, and the scarcity of double cropping opportunities. ICRISAT Village Level Studies (BinSwanger and Jodha , 1978) supplied a valuable data base for evaluation of the impact of machine threshing of 5or&~rm in a typical Indian SAT village - Kanzara, which is in the Akola d i s t r i c t ,. 1 ! hl?arashtra State.

103

The f i r s t thresher was introduced into the village in 1976 and by 1980 there were four units, two inside and mo outside the village. ?he threshing technology rapidly diffused throughout the village and mechanical threshing has a lms t entirely displaced traditional methods. Economic superiority may stem from reduced per unit cost of conmrting harvested produce into threshed grain, decreased threshing losses, and cleaner grain with lower percentage of brokcns. A fu l l report on this study is amilable (Walker and Kshirsagar, 1981). The general results from the s t d y strongly suggest that the introduction and wide- spread diffusion of mchine threshing in the village did not significant ly reduce costs, increase cropping intensity, or displace labour. The results fmm one village cannot be expected to apply to a l l of SAT India, however, they do provide a reference point for analysis of the likely consequences of machine threshing in other socio-economic and agro-climatic settings . Other Economic Studies

A project has just started a t ICRISAT on investigating marketing of groundnuts. I t i s intended to describe nurketing channels i n India and worldwide, to assess relative preferences for quality attributes as expressed in market price in India, and to assess relative world markets for confectionary versus high o i l varieties.

The Problem of Aflatoxin Contamination of Groundnuts

Aflatoxin contamination is a serious problem for the grandnut industry i n the SAT and as such is given high priority i n the ICRISAT program. Aflatoxins are toxic and carcinogenic substances produced wh& certain strains of the h g u s Aspergillus flavlis grow on g r ~ ~ d n u t s or other suitable substrates . Several factors are known to predispse gruundnut pods to invasion by A f l aws and other so i l fungi. Insects can damage shells and seeds during crop g m Z i e 1 d drying and storage, termite attack being particularly important. Such damnge can lead to invasion of seeds by A flavus. Mechanical damage to pods by cultivations or by processing machinery can similar effects. Pod-rotting fungi, which h g e , but & not always destroy pods, may facil i tate invasion of seeds by the fungus. Delayed harvesting, and slow and irregular f ield drying, can also result i n seed invasion by A flavus and other fungi comnly present in a quiescent state in shells of 'health- Drought stress, particularly during late stages of pod developnt , can also lead t o increased invasion of pods by A f laws. Seeds i n storage my be accidentally wetted by rain water, by rising g-ter, or by moisture resulting from insect infestation. Such wetting can result in rapid invasion of the gromdnuts by A flavus and other m l d fungi with consequent a flatoxin contaminat ion.

From an understanding of the factors predisposing groundnuts to invasion by A flavus and aflatoxin contamination it was possible to fornulate crop handling and storage methods which could prevent or a t least greatly reduce the risk of conatamination occurring. These methods have been applied with considerable success in countries with developed agriculture but have not been widely adopted by the small scale fanners of the SAT.

As ICRISAT is concerned with the problem a t the f a m r s ' level, and as cultural control measures have not been adopted o r have not proved successful, the research strategy followed has been that of ut i l isat ion of genetic resistance with :I V~CIJ t o developing cultivars with pods or seeds which the toxigenic A flavus cannot inkah, or , i f invaded, do not support production of a f l a t o - 7 ICRISAT houses the world collection of groundnut (Arachis hypogaea L) gezmpl-, and also has an expanding collection of wild Arachis species, there is ample mter ia l a ~ i l a b l e for screening. In th i s pa-y those aspects of the research which have relevance t o post h a m s t problem. w i l l be cowred.

3x77 Seed Resistance to Invasion by .4 flavus

I t is well known that the tcsta of an u n b g e d , mature p m d n u t seed protects the cotyledons and enbryo from invasion by seed surface contaminating imgi when the seeds are wetted or absorb misture (Carter, 1970). lrfixon and 3ogers (1973) reported that seed of the two breeding lines, PI 337394 F and PI 357109, had marked 'dry seed1 resistance to invasion and colonisation by A flavus :\hen subjected to an innoculation tes t . The tes t is carried out on u n d m k r :aturc seeds that have been dried and stored for a t least one mnth. Water i s added to a sample of approximately 20g of seed to raise their moisture contents to 20-25%. p e seeds are surface steri l ised by soaking In a 0.10, aqueous solution of rxrcuric chloride, rinsed in s ter i le water, surface i n n q a t e d with 1 m l of conidial suspension of A flavus, and then incubated a t 25 C for 8 days. The pelrentages of seeds w i m l a t i n g colonies of A f l a w are then recorded. Genotypes with up to 15% of seeds colonised are r e m s resistant, 16-30% as rcoderately resistant, 31-50% as susceptible, and over SO% as highly susceptible. Grcn~th and sporulation of the fungus is n o m l l y s p r s e on resistant seeds but dense and profuse on susceptible ones (khan & k h n a l d , 1980).

Using this tes t , some 400 germplasm lines have been screened a t ICRISAT for resistance of seeds to invasion and colonisation by toxigenic isolates of A flavus. Breeding lines reported resistant in the USA have also proved resistant in the ICRISAT tes ts and 5 new sources of resistance have been identified (Table l ) , two of which are recognised cultivars (J I1 and Faizpur).

This Idry.seed1 resistance could be of value when pods o r seeds are accidentally wetted in storage. The resistance to invasion l i e s in the testa and any damage to this organ removes or greatly reduces it. ?his i s unfortunate as several oE the decortication methods used a t the fann or village level i n the SAT can cause extensive damage t o see&. The resistance may therefore be of greater value when the groundnuts are stored i n shell,

Resistance in Gmundnuts t o Aflatoxin Pmduction

Early research reported varietal differences in aflatoxin production (Kulkani e t a l , 1967; Rao and Tulpule, 1967) when autoclaved seeds of different cultivars were colonised by toxigenic strains of A flavus. Although these claims were not confirmed by l a t e r research (Doupnik, 19-a e t a l , 1978), quantitative varietal differences were definitely indicated. The value of a genotype that would not support aflatoxin production in the event of seeds being colonised by a toxigenic strain of A flavus is obvious. Such seeds might develop high levels of free fat ty a c n would not contain aflatoxins which in many mrkets could render the produce valueless. A W f i c a t i o n of the t e s t described above for screening genotypes for 'dry seed1 resistance to A f l a w inmsion was used to screen genotypes for thei r abi l i ty to support a- production. Test seeds had their testas h g e d by scratching them with a needle. Re seeds were surface steri l ised with mrcuric chloride as already described, tkeir misture contents raised 6 20% and they were then surface innoculated . .: + a conidial suspension of a toxigenic strain of A flavus. The seeds were :x&ated a t 25% and samples remved af ter various --of time and tested ';r .?flatoxin content by the method of Nabney and Nesbitt (1965). Table 2 , i , es Aflatoxin i3 production figures for several gemtypes including some with

r e s i rzsistance t& A f l a w invasion. Unfortunately, there does not appear t o be correlazion between resistance to seed invasion by A flavus and the abi l i ty

0 2 the seed of a genotype to support aflatoxin p r o d u c t i n genotypes FESR-11- P11-B2-Bl, that showed the luwest level of aflatoxin in the t e s t illustrated, had seed which were highly susceptible t o invasion by A flavus. Figure 1, which j s taken from another experimnt, shows how the rate o-xin acamlatim '-: considerably slower in this genotype than in several others tested at the same - 5 L

1 f,A

All genotypes tested t o date, about 150 of them, have supported afla- toxin production t o som degree. Screening w i l l cmtinue and in the mantinre the plant breeden w i l l be trying t o corrbine factors for resistance of seeds to A flavus inva ion and inability of seeds t o support aflatoxin production. Genetic resistance of the &sired type would lessen the risk of aflatoxin contamination and of mould h g e i n general. However, it would s t i l l be desirable t o have good storage f ac i l i t i e s with protection from wetting and prevention of insect infestations,

References

\uj la , S S, Qlohan, J S and Mehan, V K 1978. The screening of peanut wr i c t i e s for the accumulation of aflatoxin and their relative reaction t o the toxi- genic isolate of Asperigullus f l a w s link ex Fries. Punjab Agricultural Univ J Res , 15 : 400-403.

Binswanger, H P and Jodha, N S 1978. Manual of ins tnc t ions for economic investi- gators i n ICRISATts Village Level Studies. Vol 11, Village Level S t d i e s Series, ICRISAT Economics Program, Patanchem, AP, India

Carter, J B H 1970. Studies on the growth of As r i l l u s f l a w on groundnut kernels. PhD Thesis, University 03- England) . 17Op.

'bupnik, B 1969. Aflatoxin produced on peanut varieties reported t o inhibit b production. Phytophathology , 59: 1554.

Kulkami, I G, Sharief, Y and S a m , V S 1967. "Asiriya hhitunde" groundnut gives good results i n Hyderabad. Indian Farming, 17:ll-12.

khan V K and kDonald, D 1980. Screening for resistance t o invasion and aflatoxin producion in groundnuts. Impmverrrent Program Occasional Paper 2 , p 1-15.

btixon, A C and Rogers, K M 1973. Peanut accessions resistant t o seed infection by Aspergillus f l a w . A~ron J, 65: 560-562.

Nabney, J and Nesbitt, B F 1965. A spectrophotametric mthod for determining the aflatoxins. Analyst, 90: 155-160.

Rao, K S and Tulpule, P G 1967. Varietal differences of groundnut i n the production of aflatoxin. - Nature, 214: 738739.

Walker, T S and Kashirsagar, K G 1981. The village level impact of mchine threshing and implications for technology development i n semi-arid tropical India. ICRISAT Economics Program Progress Report - 27. ICRISAT Economics Program, patan- P, India.

Cunotypr! Sou rcu P u r ~ a n t a y ~ s of sduds cnloni ziid 4y n. ~ Z U V W

Ralnyscnsnns I goo 1 511 I

US fl

Argent lnil

I!rguntinn ' a

lnbt a

Nigarln

Austral l a

Ind ia

I rrr l l a

Intl ia

S , E , + - C.V. (%)

- -- - - . . . . .

a. Lines rcfartcd rcsistanr In US/: b. Comnonl y gr&n cul r ivar

c. Susccptihl~ chack

Tablu 2. ,Iflatoxln D l producrivn in 9rounJnut cul t ivars f e ~ i ~ t m t

- - . - - -- - - - . - . - - - - -

Cul t l var React fan to s c ~ d lnvasian Aflatoxln D ,

Fa i zpur

TMV 2

FESII-l l *P 1 I -.O2-B 1

Rtslstant

k s l s t a n t

Rsslstant

Suscupt i b le

tllghly susceptlblu

OG 43-11-1 Highly surcoptlbla 76.3

G.D. (at fit)

C.V. (%I

Fig. 1: A f l a t o i i n B1 accumulation I n inoculated seeds of 4 cultivars incubated at 25 5 3&C.

Days of incubatfon fol lowlng inoculation w i t h toxigenic A, fzauus stra in AF8-3-2A