The fungus Magnaporthe grisea (anamorph Pyricularia grisea) is the causal agent of wheat blast (Triticum aestivum), an important disease for the wheat crop in Brazil. The disease is more frequent in wheat producing regions above the parallel 24 °S. The objective of the present work was to study the effect of temperature and relative air humidity in the sporulation of M. grisea. The average number of conidia was determined in raquis of wheat plants previously colonized by the fungus and exposed to growth chambers under temperatures of 23 and 28 ºC, and with relative humidity of 80, 85, 90, 95 and 100%. The number of produced conidia was determined after 24, 48, 72 and 96 hours of exposure in each combination of temperature and humidity. The effect of the temperature and the humidity was significant (P<0.001), but not the interaction. The production of conidia was also determined under natural environment conditions where temperature and the relative humidity fluctuated. The results of the present work revealed that production of conidia of M. grisea was favored by the combination of high relative humidity (> 90%) and temperature around 28 ºC.
Triticum aestivum; Pyricularia grisea; climatic factors; predictive models
