Relationship between Two Avirulence Genes: Avr-Hattan 3 and Avr-Piks

Race-cultivar specificity of the rice blast fungus complies with the ‘genefor-gene’ system. Several avirulence genes, which determine cultivar specificity have been identified and characterized (Valent and Chumley, 1994, Notteghem et al., 1994, Mandel et al., 1997, Dioh et al., 2000, Kang et al., 2001, Fukiya et al., 2001, Farman et al., 2002). However, no common features of these genes other than recognition factors have been found. The molecular mechanisms behind race-cultivar interactions might vary with the host-pathogen combinations, while the mode and frequency of the avirulence gene mutations resulting in virulent races might vary with the genes. Studies on the molecular background and evolution of race-cultivar interactions will lead to the effective use of resistance genes. In this paper, we describe and identify new avirulence genes and corresponding resistance genes in the rice blast system.