RECOMBINATION IN MAGNAPORTHE-GRISEA

The heterothallic ascomycete, Magnaporthe grisea, is the blast pathoge n of rice and about 50 other grasses, and has potential for sexual and asexual reproduction. In most populations, data from mating type, fer tility assays, and genotypic diversity strongly suggest that the patho gen is asexual. However, parasexual recombination cannot be ruled out. Chromosome length polymorphisms and translocations may prevent succes sful meiosis in most populations. Pathogens of millets and some grasse s growing with rice appear to be largely genetically isolated, though some gene flow may occur. Sexual fertility has repeatedly been reporte d in rice pathogens from mountainous regions of South and East Asia. S everal means by which sexual fertility may be lost in an agricultural setting are advanced.