Author : Lopez, Ana Liza C.

Summary : This study determined the current genetic diversity of populations of Magnaporthe oryzae , the rice blast pathogen. A total of 453 monoconidal isolates recently collected from farmers' fields and experimental plots in various geographic areas of the Philippines were genotyped using 13 micro satellite markers. Three major genetic groups, composed of 93 new multi-locus genotypes. Were determined in the collection when compared to the reference strains representing the genotypes previously published. Analysis showed that those collected from Luzon and Visayas were genetically similar while those from Mindanao were genetically different. Low diversity was noted in isolates collected from experimental plots and from lowland areas. Fertility and mating type test revealed the presence of sexually fertile isolates and both mating types MAT1.1 and MAT1.2 were found. Significant associations were noted on specific avirulence genes and types of agroecosystem. Avirulence genes would prevail in areas where the complementary resistance genes exit. Additionally, pathogenicity test identified candidate resistance genes Pil, Pi33, Pi9, Pikm and Piz-Pish, while PCR test showed the complementary resistance genes Pik, Pita and Pii to be useful in breeding for blast resistant rice cultivars. These resistance genes can be sourced from the upland varieties locally known as "Milagrosa" and "Waray".