Abstract
Nutritional indices and biochemical profile of Helicoverpa armigera in response to feeding on different groundnut genotypes was studied. The moderately resistant genotypes were ICGV 86699, ICGV 86031, ICG 2271 and ICG 1697. JL 24 was used as the susceptible check. Consumption index (CI), approximate digestibility (AD), efficiency of conversion of ingested food (ECI) and efficiency of conversion of digested food (ECD) were recorded. In addition, the activities of digestive and defensive enzymes of H. armigera were studied. H. armigera larvae showed significantly lower CI, AD, ECI and EDI when fed on moderately resistant genotypes than the insects fed on JL 24. Serine protease and trypsin activities were low in insects fed on resistant genotypes than the ones fed on JL 24. Further, insects fed on resistant genotypes showed significantly greater glutathione-S-transferase activity than the insects fed on JL 24. A reverse trend was observed for esterase activity. Similar trend was observed for total protein content of the insects. Thus, nutritional quality of host plants affects insect’s physiology and could be used as an important indicator of host plant resistance against insect pests and to understand the adaptation of insect pests, if any, to various genotypes/host plants.
Highlights
Plants face innumerable challenges from biotic and abiotic stresses, biotic stress by insect pests is one of the major stresses the plants face and take a heavy toll on crop yields
efficiency of conversion of ingested food (ECI) was significantly lower in larvae fed on genotypes ICGV 86699, ICGV 86031, ICG 2271 and ICG 1697 (21.3 – 28.2 %) than those fed on the susceptible check, ‘JL 24’ (54.1 %)
Our results showed that approximate digestibility (AD), Consumption index (CI), ECI, and efficiency of conversion of digested food (ECD) were reduced in H. armigera larvae fed on insect-resistant groundnut genotypes and were considerably lower than the insects fed on JL 24
Summary
Plants face innumerable challenges from biotic and abiotic stresses, biotic stress by insect pests is one of the major stresses the plants face and take a heavy toll on crop yields. Pesticide resistance is developed by insects, pest-resurgence, pesticide residues in food and health hazards in human beings (Isman, 2006; Sharma, 2007). Groundnut crop is affected by a number of biotic and abiotic stresses. Insect pests are the major biotic constraints of groundnut. The economically important insect pests of groundnut include western flower thrips (Frankliniella occidentalis Pergande, 1895 and melon thrips (Thrips palmi Karny, 1925); leaf miners (Aproaerema modicella [Deventer, 1904]); aphids (Aphis craccivora Koch, 1854); leafhoppers (Empoasca dolichi Paoli, 1930); white grubs (Holotrichia consanguinea Blanchard, 1850); pod borer, Helicoverpa armigera (Hübner(1808)) and armyworm, Spodoptera litura (Fabricius, 1775) (Sharma et al, 2003)
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