The noctuid pod borer, Helicoverpa armigera is one of the most damaging pests of chickpea, Cicer arietinum. The levels of resistance to H. armigera in the cultivated chickpea are low to moderate, but the wild relatives of chickpea have exhibited high levels of resistance to this pest. To develop insect-resistant cultivars with durable resistance, it is important to understand the contribution of different components of resistance, and therefore, we studied antixenosis and antibiosis mechanisms of resistance to H. armigera in a diverse array of wild relatives of chickpea. The genotypes IG 70012, PI 599046, IG 70022, PI 599066, IG 70006, IG 70018 (C. bijugum), ICC 506EB, ICCL 86111 (cultivated chickpea), IG 72933, IG 72953 (C. reticulatum), IG 69979 (C. cuneatum) and IG 599076 (C. chrossanicum) exhibited non preference for oviposition by the females of H. armigera under multi-choice, dualchoice and no-choice cage conditions. Based on detached leaf assay, the genotypes IG 70012, IG 70022, IG 70018, IG 70006, PI 599046, PI 599066 (C. bijugum), IG 69979 (C. cuneatum), PI 568217, PI 599077 (C. judaicum) and ICCW 17148 (C. microphyllum) suffered significantly lower leaf damage, and lower larval weights indicating high levels of antibiosis than on the cultivated chickpea. Glandular and nonglandular trichomes showed negative correlation with oviposition, while the glandular trichomes showed a significant and negative correlation with leaf damage rating. Density of non-glandular trichomes was negatively correlated with larval survival. High performance liquid chromatography (HPLC) fingerprints of leaf surface exudates showed a negative correlation of oxalic acid with oviposition, but positive correlation with malic acid. Both oxalic acid and malic acid showed a significant negative correlation with larval survival. The wild relatives exhibiting low preference for oviposition and high levels of antibiosis can be used as sources of resistance to increase the levels and diversify the basis of resistance to H. armigera in cultivated chickpea.

Wild relatives of crops are an important source of resistance genes against insect pests. However, it is important to identify the accessions of wild relatives with different mechanisms of resistance to broaden the basis and increase the levels of resistance to insect pests. Therefore, we evaluated 15 accessions of wild relatives of chickpea belonging to seven species and five genotypes of cultivated chickpea for their resistance to pod borer, Helicoverpa armigera, which is the most damaging pest of chickpea. The test genotypes were evaluated for resistance to H. armigera using detached pod assay. Data were also recorded on activity of the digestive enzymes in the midgut of the larvae fed on different wild relatives of chickpea. All the wild chickpea genotypes suffered lower pod damage and weight gained by the third-instar larvae of H. armigera was lower when fed on them compared with the cultivated chickpea. The accessions, IG 69979 (Cicer cuneatum), PI 599066, IG 70006, IG 70018, IG 70022 (Cicer bijugum), IG 599076 (Cicer chrossanicum), and IG 72933, IG 72953 (Cicer reticulatum), showed high levels of resistance to H. armigera. There were significant differences in protease activity in larval gut of H. armigera fed on different wild relatives of chickpea. Total protease, trypsin, and chymotrypsin activities were lowest in larva fed on PI 599066 (C. bijugum) compared with that in the larvae fed IG 69979 (C. cuneatum) and IG 70022 (C. bijugum). Aminopeptidase activity was highest in the larvae fed on IG 70022 (C. bijugum) and IG 599076 (C. chrossanicum), whereas lowest activity was recorded in the larvae fed on ICC 3137 and KAK 2 (susceptible checks). The variation in protease activities may be due to the presence of protease inhibitors in the wild relatives or hyperproduction of enzymes by the larvae as result of protease inhibitor activity of the wild relatives, resulting in low weight gain by larvae. The results suggested that wild relatives of chickpea with diverse mechanisms of resistance can be exploited to increase the levels and diversify the basis of resistance to H. armigera in cultivated chickpea.

Efforts are being made to develop chickpea varieties with resistance to the pod borer, Helicoverpa armigera for reducing pesticide use and minimizing the extent of losses due to this pest. However, only low to moderate levels of resistance have been observed in the cultivated chickpea to this polyphagous pest. Hence, it is important to explore wild relatives as resistance sources to develop insect-resistant cultivars. Therefore, we studied different biochemical components that confer resistance to H. armigera in a diverse array of wild relatives of chickpea. Accessions belonging to wild relatives of chickpea exhibited high levels of resistance to H. armigera as compared to cultivated chickpea genotypes in terms of lower larval survival, pupation and adult emergence, decreased larval and pupal weights, prolonged larval and pupal developmental periods and reduced fecundity of the H. armigera when reared on artificial diet impregnated with lyophilized leaf powders. Amounts of proteins and phenols in different accessions of chickpea wild relatives were significantly and negatively correlated with larval weight, pupation and adult emergence. Phenols showed a negative correlation with pupal weight and fecundity, but positive correlation with pupal period. Total soluble sugars showed a negative correlation with larval period, but positive correlation with pupation and pupal weight, while tannins showed a positive correlation with larval weight, pupation and adult emergence. The flavonoid compounds such as chlorogenic acid, ferulic acid, naringin, 3,4-dihydroxy flavones, quercetin, naringenin, genistein, biochanin-A and formononetin that were identified through HPLC fingerprints, exhibited negative effects on survival and development of H. armigera reared on artificial diet impregnated with lyophilized leaf powders. The wild relatives with diverse mechanisms of resistance conferred by different biochemical components can be used as sources of resistance in chickpea breeding programs to develop cultivars with durable resistance to H. armigera for sustainable crop production.