EVIDENCE OF A GENE-FOR-GENE RELATIONSHIP IN THE ORYZA-SATIVA-MAGNAPORTHE-GRISEA PATHOSYSTEM

A cross was made between two field isolates of Magnaporthe grisea pathogenic to rice. Full-sib crosses between F1 ascospores, followed by backcrosses to the female fertile parent GUY11, produced perithecia fertile enough for tetrad isolation. Genetic analysis of the pathogen revealed that avirulence to the rice cultivar Pi-n-degrees-4 is controlled by one gene (Avr1-Pi-n-degrees-4) unlinked to the gene MAT1-1, which is responsible for mating type. Additionally, resistance of Pi-n-degrees-4 was found to be controlled by one gene. Thus, existence of a gene-for-gene relationship was shown for the pathosystem Oryza sativa-M. grisea.