Rela？？o entre o teor de clorofila nas folhas e a severidade de brusone nas panículas em arroz de terras altas

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 bonan？a 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.