Effect of Zinc on the Development of Brown Spot in Rice

Abstract

Brown spot, caused by the fungus Bipolaris oryzae, is one of the most destructive diseases of rice. This study investigated the effect of zinc rates on the development of brown spot in rice. Rice plants (cv. ‘Metica-1′) were grown in hydroponic culture amended with Zn rates (applied as ZnSO4.7H2O) of 0, 0.5, 1, 2 and 4 μm and inoculated with B. oryzae. The foliar concentration of Zn was determined. Leaf samples were assessed for disease severity, and then, area under brown spot progress curve (AUBSPC) was calculated. The relationship between Zn concentrations on leaf tissues and the rates of this micronutrient was best described by a positive linear regression model, while the relationship between the Zn rates and the AUBSPC was best described with a positive quadratic regression model. The correlation between Zn concentrations on leaf tissues and AUBSPC was positive and significant (r = 0.68, P < 0.05). The results from this study showed that high foliar concentration of Zn was associated with increasing rice susceptibility to brown spot.