Effect of Magnaporthe grisea on Seed Germination, Yield and Quality of Wheat

The effect of wheat blast, caused by Magnaporthe grisea (Pyricularia grisea), on seed germination, yield loss and grain quality was evaluated during the growing season of 2005 in wheat cultivars BRS208 and CD104 in Sao Paulo State, Brazil. Each field was divided in an imaginary diagonal line crossing the center and then five areas of one m2$ each separated 10 m were selected. Cultivars differed significantly in their reaction towards blast. The BRS208 showed to be more susceptible with incidence of 76.2%, higher severity and yield loss of 662.2 kg/ha or 32.2% whereas CD104 had lower incidence (32%), severity and yield loss (399.1 kg/ha or 13.9%). Although a clear difference was detected between weight of 100 seeds from healthy-looking and blast diseased heads there was no difference in seed infection, which ranged from 68.6 to 83.1% in these two cultivars. Moreover there was no correlation between seed infection and germination in any cultivar. Seeds from blast diseased heads had higher proteins contents whereas lipids remained unaffected. Finally it is worth stressing that incidence of disease, yield loss and other parameters evaluated in this work were carried out in a commercial field with two applications of fungicides. The present data showed the inefficacy of chemicals to control wheat blast and that the disease continues to be one major problem of wheat in Brazil.