Influence of Bottle Gourd Cultivars on the Biology and Demographic Parameters of Helicoverpa Armigera (Hübner, 1809): Basis of Resistance Through Biochemical and Physiological Approach.

Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is an important herbivorous pest of bottle gourd. We studied the development, reproduction and life table parameters of H. armigera to assess the resistance of eight bottle gourd cultivars, and performed biochemical analysis when H. armigera fed on two more susceptible cultivars [ANKUR AMIT (AMIT) and MALLIKA] and two less susceptible cultivars [KSP-1720 and ANKUR GOLU (GOLU)]. Significantly lower digestive enzymes (amylase, sucrase and lipase), higher detoxification enzymes (carboxylesterase, glutathione-S-transferase and mixed-function oxidase) and greater antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), polyphenol oxidase (PPO), peroxidase (POD) and ascorbate peroxidase (APX)] were observed in fifth instar H. armigera after feeding on two less susceptible cultivars (KSP-1720 and GOLU) than in two more susceptible cultivars (AMIT and MALLIKA). Further, significantly lower amounts of nutrients (glucose, fructose, sucrose and protein), higher amounts of secondary metabolites (flavonol), and higher activities of antioxidant enzymes (SOD, CAT, POD and APX) and lipoxygenase 3 (LOX3) were recorded in GOLU (less susceptible) than in AMIT (most susceptible), MALLIKA and KSP-1720 when fed by H. armigera caterpillars. The RT-PCR test of three genes for antioxidant enzymes (LsSOD, LsCAT and LsPOD) was more upregulated in GOLU than in AMIT when fed by H. armigera caterpillars, suggesting that GOLU is the less susceptible cultivar and AMIT is the most susceptible cultivar. Therefore, GOLU cultivar suffered lower H. armigera damage by decreasing plant nutrients, and increasing plant secondary metabolites and antioxidant enzymes. This research will help in developing standard regulations to appraise H. armigera-resistant bottle gourds.