H.M. VamadevaiahRashmi R.2017-03-062017-03-06http://krishikosh.egranth.ac.in/handle/1/5810004238A pot experiment was conducted at ARS Dharwad farm during kharif 2013 to study the effect of insect damage and mechanical damage followed by insect damage on expression of biochemical metabolites namely total sugars, reducing sugars, non-reducing sugars, total phenol, condensed tannin, gossypol, available potassium, nitrate reductase, peroxidase and lipoxygenase in Laxmi and Sahana genotypes at 45 DAS, 85 DAS, 125 DAS. The experiment was conducted in factorial CRD with three replications. Significant differences were observed with respect to genotypes due to different treatments viz., insect (H. armigera) damage and mechanical damage followed by insect damage at different stages. Significant increase in total sugars, non reducing sugars, total phenol, condensed tannin, gossypol, potassium, nitrate reductase activity, peroxidase activity and lipoxygenase activity in Sahana than Laxmi genotype. Insect survivability was significantly lower in mechanically damaged plants than in undamaged plant in both the genotypes and insect survivability was less in Sahana genotype when compared to Laxmi genotype. This study reports the impact of insect (H. armigera) damage and mechanical damage followed by insect damage on cotton host-plant resistance due to biochemical metabolites. It is proposed that cotton plant damaged by H. armigera exhibit resistance and cotton plant damaged by mechanical means is less preferred for the growth of H. armigera. This is probably due to a reduction in the nutritive quality (Total sugar, Reducing sugar), induction of allelochemicals, such as total phenols, condensed tannin, gossypol and of oxidative enzymes, such as lipoxygenase, peroxidase and nitrate reductase in the damaged plants.ennullThesis