Latest genotype of cotton plant resistance on the basis of its biochemical analysis against aphids

Resistance is an effective part of integrated pest management in host plant while by keeping in view the biochemical mechanisms that could fast the resistance breeding.  To study the biochemical mechanisms of cotton plant resistance to its major sucking insect pests like aphids, sixteen cotton genotypes with various degree of resistance were planted in growth chambers and a field with four replications.  Phenolics protein, sugars, chlorophylls and carotenoids were extracted from plant leaves, and damage by and numbers of aphids in different species were recorded.  Aphid’s stings per cm² leaf area of young plants were highly correlated with sting/cm² of mature plants.  This suggests that aphid resistant varieties for mature cotton plants may also be deployed for baby leaf production. Sucrose concentration of young plants was correlated with aphids stings per cm² leaf (r = 0.720, p = 0.01) and mines per plant (r = 0.780, p = 0.01), suggesting that low sucrose content could be used as a marker for early screening or selection for aphid resistance.  Aphids stings/cm² were negatively associated with contents of flavonoids (r = -0.550, p = 0.05) and chlorogenic acid (r = -0.588, p = 0.05), while stings per plant were negatively associated with concentrations of flavonoid (r = -0.700, p = 0.01), chlorogenic acid (r = -0.595, p = 0.05) and rutin (r = -0.602, p = 0.05), implying a role of phenolics in the aphid resistance.  Total number of apterous aphids including Myzus persicae, Macrosiphum euphorbiae and Aulacorthum solani per 100 g plant weight was correlated with contents of protein (r = 0.890, p = 0.01), b-carotene (r = 0.828, p = 0.01), lutein (r = 0.819, p = 0.01), chlorophyll (r = 0.738, p = 0.01), and glucose (r = -0.760, p = 0.01) of young cotton plants, which could be early indicators of aphid resistance.  Aphids per 100 g plant weight were also associated with chicoric acid concentration of mature cotton plant (r = 0.749, p = 0.01).  The purpose of this study is to make insights into the mechanism of resistance to aphids as well as screening and selection tools for breeding insect-resistant cotton.