Relationship between panicle blast severity and mineral nutrient content of plant tissue in upland rice.

Panicle blast (Pyricularia grisea) in upland rice causes significant yield losses depending upon the environmental conditions and nutritional status of the plant at the grain-filling stage. Four field experiments were conducted to evaluate the influence of mineral nutrients on panicle blast of four upland rice genotypes on an oxisol. Panicle blast severities of four genotypes were related to nutrient concentrations in panicle tissues. Nitrogen (N), phosphorus (P), and magnesium (Mg) contents in tissue were significantly (P<0.01) and positively correlated, whereas potassium (K) and calcium (Ca) were negatively correlated with panicle blast severity. While the relationship between tissue N concentration and disease severity was quadratic, it was linear for K concentration. The correlation between tissue contents of N and P were positive and highly significant (r=0.75 P