et al. 2003a, b). The environmental conditions that support disease development are similar among the M. oryzae Oryza, Lolium, and Triticum relatives (Anderson et al., 1947; de Andrade Cardoso et al. 2008; Uddin et al. 2003a). However, in temperate regions, populations of the M. oryzae Lolium and Oryza pathotypes are reduced by winter conditions (Harmon and Latin 2003; Kapoor and Singh 1977; Latin and Harmon 2004). For instance, wintertime freezing temperatures limit the survival of the M. oryzae Lolium pathotype in some U.S. areas (Harmon and Latin 2003, 2005; Latin and Harmon 2004).