Cotton leaf curl virus (CLCuV), transmitted by whitefly Bemisia tabaci, causes one of the most devastating diseases of cotton. Disease symptoms, which appear on leaves, are thickening of midribs and veins and development of enation. Disease resistant cotton cultivar CIM-448 had high leaf epicuticular wax. Electron micrographic of midribs showed the sever effects of virus on vascular elements in S-12 (CLCuV susceptible), whereas no such effects were observed in NIAB-Krishma (moderately CLCuV-resistant) and CIM-448 (CLCuV-resistant) reflecting their differential degree of resistance to CLCuV.
To probe the relationships between some macro-nutrients like N, P, K and Ca and resistance to cotton leaf curl virus (CLCu V) in cotton, two genetically different cultivars (S-12, CLCuV susceptible and CIM-448, CLCuV resistant) were grown in sand culture under high and low N, P, K and Ca regimes in respect of that in full strength of Hoagland’s nutrient solution. The varying N regimes of the growth medium were 224,112, and 56 mg L-l in Hoagland's nutrient solution. Similarly, for P, 62.00, 31.00, 15.50 and 3.88 mg L-l, for K, 236,120, and 40 mg L-1, and for Ca, 320,160,80, and 20 mg L-l were maintained in Hoagland’s nutrient solution. Leaf epicuticular wax, chlorophyll a, b and a/b ratio, soluble proteins, free amino acids, water relation parameters and gas exchange properties were measured. After harvest, fresh and dry biomass, leaf area, ion contents, soluble sugars and starch content of the plant tissues were determined.
From all these results, it was evident that highly disease resistant CIM-448 and highly susceptible S-12 were less affected by alteration in nutrition. S-12 remained susceptible under various nutrients except at lower N and P, at which growth and virus 2incidence had been reduced to some extent. However, higher external K concentrations in susceptible plants alleviated disease incidence. Patterns of ion accumulation were same in both cultivars under altered as well as under normal conditions. Pattern of accumulation of soluble sugars and free amino acids were also same as under normal conditions. Although disease cannot be eliminated by any specific nutrient, but incidence of disease was reduced particularly with the addition of K. From the results presented here, it is recommended that disease incidence can be considerably reduced by N, P, and K nutrition in proper combination. All this work will widen our existing knowledge and provide basis for modifying current agricultural practices to reduce disease incidence in cotton.