author(s)
Appala Raju A, Sesha Mahalakshmi M, Sandhya Rani C and Adinarayana M

abstract
The study was conducted during kharif, 2016-17 at Regional Agricultural Research Station (RARS), Lam, Guntur, Andhra Pradesh, with objectives to study of morphological and biochemical factors responsible for insect resistance. The study highlighted that Morphological characters like leaf thickness and leaf hair density of cotton leaf, biochemical components viz., phenols and tannins were quantified to find out the characters of cotton plant that are associated with tolerance or resistance to leafhoppers. The results revealed that, variation in leaf thickness was very narrow and found non-significant among all the genotypes both at vegetative stage as well as flowering stage. The genotypes, which recorded significantly higher hair density on leaf lamina and midrib at vegetative and flowering stage harboured lower population of leafhoppers. Thus, the present results revealed that the genotypes with more leaf hair density were found to be resistant against leafhoppers. DCH-32 possessing low hair density recorded significantly higher mean leafhopper incidence (24.0 no. of leafhopper/3 leaves/plant). The genotypes recorded more per cent phenol content and tannin content recorded less number of leafhoppers. Hence it can be concluded that the genotypes possessing more phenols and tannins exhibited resistance or tolerance against leafhoppers. The highest seed cotton yield was recorded in GISV-267 (18.5 q/ha), GJHV-497 (18.4 q/ha) and GSHV-173 (18.1 q/ha) which were found to be leafhopper resistant.