Rice blast (Magnaporthe oryzae) is the most important yield limiting factor of upland rice in Brazil. The nitrogen application rate and planting date determine the level of panicle blast severity. A field experiment was conducted with the cultivar BRS Bonança to establish the relationship between chlorophyll content in leaves and panicle blast severity. The layout was a randomized split plot design with three replications. The treatments included 12 planting dates at weekly intervals and five rates of nitrogen (0, 30, 60, 120 and 240 kg ha-1 of N). The chlorophyll content was measured on flag leaf with a chlorophyll meter. Panicle blast severity increased significantly with the increase in nitrogen fertilization. The correlation between nitrogen rate and chlorophyll content in flag leaf was positive and significant (r=0.98; p < 0.01). The relationship between panicle blast severity and chlorophyll content was linear and positive (r= 0.99; p < 0.01). The chlorophyll content in the flag leaf can be included as independent variable in the development of a mathematical model for panicle blast forecasting.
Oryzae sativa; Pyricularia grisea; epidemiology
