Relationship Between the Nutritional and Physiological Responses of Helicoverpa armigera (Hübner) and Phytochemical Metabolites in Various Sesame Cultivars

The cotton bollworm, Helicoverpa armigera (Hübner), is one of the significant economic pests of agricultural crops. In the current study, the nutritional indices and digestive enzymatic activities of H. armigera were assessed on 10 sesame cultivars (Barekat, Mohajer, Shevin, Chamran, Jiroft, Behbahan, Sistan, Dashtestan, Dezful and Hamidieh). Furthermore, specific phytochemical metabolites of sesame cultivars (protein, starch, lipid, phenol, flavonoid and anthocyanin) were evaluated to investigate their relationships with the nutritional and physiological responses of the pest. The results revealed that the efficiency of conversion of ingested food (ECI), efficiency of conversion of digested food (ECD) and relative growth rate (RGR) values of H. armigera larvae were highest on Mohajer and Barekat. However, the related lowest amounts were obtained on Chamran, Jiroft and Dezful. The highest level of amylolytic activity in H. armigera larvae was detected on Jiroft, whereas the lowest activity was found on Mohajer. The larvae fed on Barekat, Mohajer, Dashtestan and Dezful exhibited the maximum proteolytic activities. Quantifying the biochemical differences of the studied sesame cultivars revealed significant variation. Furthermore, significant negative or positive correlations were found between the nutritional indices with enzymatic activities of H. armigera larvae or both of these traits with the chemical components of the tested sesame cultivars. The cluster analysis results revealed that Mohajer and Barekat were the most suitable cultivars, while Chamran, Jiroft and Dezful were nutritionally unsuitable for H. armigera. Our findings suggest that the selective use of certain sesame cultivars as potential sources of antibiosis against H. armigera could be incorporated into integrated pest management (IPM) programmes or used to screen insect inhibitors for developing genetically modified pest-resistant plants.