Occurrence of blast fungus (Pyricularia grisea) on wheat and rye in the savanna region of central Brazil

Abstract

The present work reports the natural occurrence of blast in wheat and rye in the Savanna region of Central Brazil. In May 1993, on a field trail of the Internacional Heat Stress Genotype Experiment at the Cerrados Agricultural Research Center (EMBRAPA-CPAC), Planaltina, DF, symptoms on the heads of the wheat cv. Kanchan showed similarities to that described in the literature for the wheat blast. The confirmation of the causal agent, Pyricularia grisea (Cooke) Sacc., was made after isolation on PDA medium and observation of morphological characteristics of the fungus using light microscope. Under field conditions, the whiteness symptoms had attained 48.6% of the heads. These infected heads showed a 7.4% reduction in fertile spikes and 10.4% reduction in the number of grains when compared to unaffected ones. The reduction in the grain weight per head at disease levels up to 50% and above were 8% and 29%, respectively. In March 1995, symptoms of the leaf whiteness of the heads were also observed on wheat cv. BR 10-Formosa, and rye cv. BR 1 crops at CPAC. The occurrence of P. grisea was confirmed as described above.