Constitutive and induced biochemical defense in buds of wild crucifers against mustard aphid [Lipaphis erysimi (Kaltenbach)]

Mustard aphid, infestation causes significant reduction in oil content in rapeseed-mustard. Plant-aphid interactions are influenced by phytochemicals that help to defend plants against biotic stresses. Since resistance level to aphids in cultivated Brassica juncea are low to moderate, it is crucial to identify resistant sources in wild crucifer against this pest. This study evaluated both constitutive and aphid induced biochemical traits in 32 wild crucifer genotypes (29- wild species and 3- B. juncea cultivars as check) and examined their impact on developmental biology of L. erysimi. Results showed that the nymphal, developmental, reproductive period of L. erysimi significantly prolonged while survival and fecundity were lower on wild crucifers as compared to check. The nutritional, antinutritional composition and enzymatic activity varied significantly among the test genotypes under both uninfested and aphid-infested conditions, suggesting their role in mitigating oxidative stress and providing defense against aphids. Furthermore, the study also revealed that constitutive and aphid-induced biochemical traits explained 74.5 to 92.2% and 55.9 to 91.3% of the variations in the biological parameters of aphids respectively. Among the test species, Brassica fruticulosa, Diplotaxis erucoides, D. siettiana, D. assurgens, Eruca sativa, Crambe abyssinica and Lepidium sativum, exhibited a significant increase in biochemical levels in responses to aphid feeding, which negatively affected the developmental biology of L. erysimi. These findings underscore the potential of these wild crucifers as valuable genetic resource for developing aphid resistant cultivars of Indian mustard.