REDUCING DISEASE INCIDENCE OF COTTON LEAF CURL VIRUS (CLCUV) IN COTTON (GOSSYPIUM HIRSUTUM L.) BY POTASSIUM SUPPLEMENTATION

Abstract

Severity of various diseases in plants can be reduced by nutrient management. The knowledge of K nutrition on relationship between plants and pests may help in devising strategies to set up high yielding production system by reducing disease incidence. Therefore, two cotton (Gossypium hirsutum L.) cultivars, S-12 (CLCuV-susceptible) and CIM-448 (CLCuV-resistant) were supplied with varying concentration of potassium [40, 120, and 236 mg K L-1]. During the experiment, only virus susceptible cultivar S-12 exhibited typical disease symptoms on leaves, while that of CIM-448 did not show any degree of disease incidence. Moreover, at lower K supply, severity of disease incidence significantly enhanced. Although growth of both cotton cultivars decreased at low K concentration, cv. CIM-448 was superior in growth than that of virus susceptible cv. S-12 at all K concentrations. Virus resistant cultivar, cv. CIM-448 had higher leaf epicuticular wax than that of cv. S-12. However, it is interesting to note that diseased leaves of cv. S-12 had greater epicuticular wax content than that of healthy leaves of cv. S-12. Leaf K+ decreased with decrease in K regimes in both cultivars. Diseased leaves of virus susceptible cv. S-12 had higher leaf Ca2+ and N than those in healthy leaves of cvs. S-12 and CIM-448, whereas CIM-448 had higher leaf Mg2+ as compared to diseased or healthy leaves of S-12. Total soluble proteins, total free amino acids, total soluble sugars did not show any relationship with disease incidence. Photosynthetic rate and stomatal conductance were higher in CIM-448 than that in cv. S-12. Moreover, photosynthetic rate was higher in healthy leaves of cv. S-12 than that of diseased leaves. Chlorophyll ‘a’ was higher in cv. CIM-448 than that in the leaves of cv.S12. In conclusion, low supply of K decreased the growth of both cultivars, but it also increased the severity of disease incidence in cv. S-12. Increase in disease incidence in cv. S-12 is possibly associated with lower photosynthetic pigments, lower rates of photosynthesis, and lower K and N use efficiency and low accumulation of Mg2+in the leaves.