Leaf rust resistance of spring, facultative, and winter wheat cultivars from China

Leaf rust, caused by Puccinia triticina, is an important disease of wheat ( Triticum aestivum) in China. Sixty-one spring and 102 facultative or winter growth habit wheat cultivars from China and a set of testers, carrying nam ed Lr genes, were evaluated for resistance at the seedling growth stage wit h an array of Mexican Puccinia triticina races. Variation in seedling infec tion types of the cultivars was compared with that of the testers, and gene s conferring low infection types were postulated. In total, nine named gene s, Lr1 (in 13 cultivars), Lr3 (12), Lr3bg (2), Lr10 (1), Lr13 (4), Lr14a (1 ), Lr16 (49), Lr23 (9), and Lr26 (81), were identified. Thirty-one cultivar s displayed intermediate reactions to one or more races that could not be a ttributed to any named gene. Twenty-eight spring cultivars were also evalua ted at two field sites in Mexico using two common races. About half of them displayed good to moderate adult resistance that may be partly due to the presence of slow rusting gene Lr34 in at least seven cultivars. Diversity i n adult plant responses of these wheats indicated the presence of additiona l slow rusting genes. Presence of 1B.1R translocation in 12 wheat cultivars , supposedly derived from intergeneric crosses involving T. durum, Haynaldi a villosa, and Avena fatua, indicated that their pedigrees were incorrect.