Finding the basis of resistance among bottle gourd cultivars to Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) in the context of biochemical and physiological approach

Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is an important pest of Lagenaria siceraria (Molina) Standl. (bottle gourd). Biology of H. armigera was conducted on eight bottle gourd cultivars (ANKUR AMIT, MALLIKA, KSP-1499-TARZAN, BSS-1010, BSS-687-KUNDAL, KSP-1722, KSP-1720 AND ANKUR GOLU) through the age-stage, two-sex life table approach. The growth, development and fecundity, including life table parameters of H. armigera were better on two more susceptible bottle gourd cultivars (ANKUR AMIT and MALLIKA) and poor on two less susceptible cultivars (KSP-1720 and ANKUR GOLU). The nutrients (total proteins, amino acids, glucose, fructose and sucrose) and secondary metabolites [total phenols, flavanols, tannins and malondialdehyde (MDA) content were determined on two more susceptible bottle gourd cultivars (ANKUR AMIT and MALLIKA) and poor on two less susceptible cultivars (KSP-1720 and ANKUR GOLU) after feeding for 6 hr or 12 hr by fifth instar H. armigera caterpillars. The antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), polyphenol oxidase (PPO) and peroxidase (POD)] and activity of lipoxygenase3 (LOX3) were estimated on two more susceptible bottle gourd cultivars (ANKUR AMIT and MALLIKA) and poor on two less susceptible cultivars (KSP-1720 and ANKUR GOLU) after feeding for 6 hr or 12 hr by fifth instar H. armigera caterpillars. The activities of digestive enzymes (amylase, lipase and sucrase) were measured in fifth instar H. armigera caterpillars on two more susceptible bottle gourd cultivars (ANKUR AMIT and MALLIKA) and two less susceptible cultivars (KSP-1720 and ANKUR GOLU) after feeding for 6 hr or 12 hr. The antioxidant enzymes (SOD, CAT, APX, PPO and POD) were measured in fifth instar H. armigera caterpillars on two more susceptible bottle gourd cultivars (ANKUR AMIT and MALLIKA) and two less susceptible cultivars (KSP-1720 and ANKUR GOLU) after feeding for 6 hr or 12 hr. To understand the resistance mechanism of the less susceptible bottle gourd cultivar (ANKUR GOLU) against the most susceptible bottle gourd cultivar (ANKUR AMIT), two nutrient synthesis genes [nitrate reductase (NR) and pyrrolin-5-carboxylic acid synthetase (P5CS)] and three antioxidant enzyme coding genes [superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD)] were subjected to transcription analysis. All the results showed that ANKUR AMIT is the less susceptible cultivar to H. armigera. Therefore, it is suggested that the ANKUR AMIT bottle gourd cultivar could be promoted for bottle gourd yield.