Role of biochemical traits for resistance to cotton leaf curl disease (CLCuD) in Gossypium hirsutum L.

Cotton leaf curl disease (CLCuD) is a major biotic constraint that can significantly reduce the crop productivity. Development of resistant variety is most effective method to tackle with this and the successful exploitation of source of resistance requires information on the biochemical traits imparting resistance to CLCuD. We examined the role in imparting resistance to CLCuD of different biochemical traits including total sugar, phenols, gossypol, tannin, crude protein contents and enzymatic activities of peroxidase and polyphenoloxidases in resistant and susceptible cotton genotypes and their F1s at two different growth stages by using their standardized methods. Four genetically diverse cotton genotypes i.e. two resistant (GCH 3 and H 1353) and two highly susceptible to CLCuD (HS 6 and RST 9) were identified from the germplasm during 2013; four F1 hybrids were developed by crossing these genotypes and raised during kharif 2014 and finally evaluated under field conditions in 2015. Two factor analysis depicted that the amount of total phenol, gossypol, tannin, protein and activities of peroxidase & polyphenoloxidase was significantly higher in leaves of resistant genotypes than susceptible genotypes at different growth stages. Also, the significantly higher concentrations of these constituents in resistant genotypes after infection suggested that there is a correlation between increased levels of these constituents and plant resistance. So, these constituents might play an active role in imparting resistance to CLCuD and provide defense mechanism to plants which suggested that these traits could serve as potential biochemical markers and further may be used for early screening of germplasm lines.