Alteration in the developmental physiology of Maruca vitrata (Fabricius) on jasmonic acid and salicylic acid treated pigeonpea

Spotted pod borer, Maruca vitrata (F.), is one of the severe threats to grain legumes in the tropics and subtropics owing to its destructiveness and broad host range. It is imperative to look for safer alternatives for its management, such as the utilization of host plant resistance which can be induced upon the exogenous application of jasmonic acid (JA) and salicylic acid (SA). We studied the changes induced in the digestive and detoxifying enzymes of M. vitrata upon its feeding on JA and SA-treated pigeonpea plants in comparison with the untreated plants. Both JA and SA induced a defense response in pigeonpea plants against M. vitrata, which in turn affected the pest’s development and physiology. The effect on the digestive enzymes (amylase, total proteases, elastase, lactate dehydrogenase) and developmental parameters (larval duration, larval weight, pupal weight, pupal percent, adult emergence and adult longevity) of M. vitrata was more pronounced and significant in the plants pre-treated with JA and then infested with M. vitrata after 12 h of JA application, compared to other treatments and untreated plants. The resistant genotype, AL 1747 responded better to the exogenous application of elicitors and M. vitrata infestation than the susceptible genotype MN 1. As a counter-response to induced plant defenses, an increase in the activity of glutathione-S-transferases (GST) and glucose oxidase (GOX) enzymes was observed in M. vitrata. Despite elevating its GOX activity upon elicitor application, the pod borer was unable to overcome the induced pigeonpea defences consequent of elicitor application as was indicated by its reduced larval weight and other biological parameters. SA also altered the activities of digestive and defense-related enzymes in M. vitrata; however, the effect was not as pronounced as JA. Both JA and SA seem to be involved in triggering the pigeonpea defenses and their exogenous application can be utilized to develop sustainable pest management strategies against M. vitrata.