RELATIONSHIP BETWEEN PANICLE BLAST SEVERITY AND MINERAL NUTRIENT CONTENT OF PLANT-TISSUE IN UPLAND RICE

Panicle blast (Pyricularia grisea) in upland rice causes significant y ield losses depending upon the environmental conditions and nutritiona l status of the plant at the grain-filling stage. Four field experimen ts were conducted to evaluate the influence of mineral nutrients on pa nicle blast of four upland rice genotypes on an oxisol. panicle blast severities of four genotypes were related to nutrient concentrations i n panicle tissues. Nitrogen (N), phosphorus (P), and magnesium (Mg) co ntents in tissue were significantly (P < 0.01) and positively correlat ed, whereas potassium (K) and calcium (Ca) were negatively correlated with panicle blast severity. While the relationship between tissue N c oncentration and disease severity was quadratic; it was linear for K c oncentration. The correlation between tissue contents of N and P were positive and highly significant (r=0.75 P < 0.001). Micronutrient tiss ue concentrations were not significantly correlated to panicle blast s everities except for zinc (Zn). The low panicle blast severities of im proved cultivar Guarani were associated with high K and Zn and low N, P, and Mg tissue concentrations.