Abstract
Resistance to the pathogens of snow mold, especially to Typhula ishikariensis S. Imai is one of the most important traits in wheat breeding for the central region of Hokkaido. T. ishikariensis always occurs in wheat nurseries when snow melts, at Hokkaido Natl.. Agric. Ext. Stn., where the snow mold resistance of winter wheat is being studied. Since T. ishikariensis consists of biotype A, B and C, it is considered that the resistance of winter wheat to each biotype should be determined. T. ishikariensis biotypes A, B and C which were cultured in a vermiculite-wheat bran medium were used as inoculum source. Five wheat varieties, PI 173438 (highly resistant), Horoshirikornugi (resistant), Takunekomugi (moderately resistant), Chihokukomugi (moderately susceptible) and lbis (susceptible) were treated with the inocula after the onset of a continuous snow cover in 1985 and 1986. In the plots inoculated with biotype A, PI 173438 always exhibited higher resistance to the fungi than the other varieties, but the damage of the wheat varieties inoculated with biotype B or C was so serious that the difference in resistance among the wheat varieties could not always be detected (Table 2, 3 and 4). Snow mold damage of wheat varieties inoculated with T.
