Role of secondary metabolites biosynthesis in resistance to cotton leaf curl virus (CLCuV) disease
Disease percentage on six cotton varieties with respect to time for cotton leaf curl virus (CLCuV) was evaluated. In August 2007, the maximum disease was observed in CIM-506, CYTO-89 and BH-118 (susceptible), whereas CIM-443 was resistant with lower disease percentage. It was found that the leaf area, fresh weight and dry weight were more in healthy sample of leaves as compared to diseased samples of same varieties. Maximum leaf area was observed in BH-118 in healthy sample as compared to diseased ones and minimum leaf area was observed in CYTO-89. Maximum fresh weight and dry weight were present in NIAB-111 and CIM-443 in healthy sample as compared to diseased sample, respectively. Secondary metabolites production in healthy and diseased sample of leaves of cotton varieties after the attack of CLCuV found maximum phenolics, carotenoids, chlorophyll a, chlorophyll b and total chlorophyll a and b in healthy sample and minimum contents present in diseased sample. CIM-446 was the best variety to resist the cotton leaf curl disease. CIM-446 had maximum chlorophyll contents as compared to diseased leaves, and maximum phenolics were present in BH-118 and carotenoids in NIAB-111 in healthy sample in resistance to CLCuV. So, CIM-446, CIM-443, NIAB-111 and BH-118 were the best varieties in resistance to cotton leaf curl disease. The productions of secondary metabolites were high in healthy leaves in resistance to cotton leaf curl disease.
Key words: Cotton varieties, cotton leaf curl disease percentage, leaf area, fresh and dry weight, chlorophyll a, b, a + b, carotenoids, phenolics.