Characterization of a New Powdery Mildew Resistance Gene on Chromosome 1R from Hexaploid Triticale Transferred to Wheat

Powdery mildew, caused by <i>Blumeria graminis</i> f. sp. <i>tritici</i>, is a highly destructive disease affecting wheat in most growing regions worldwide. The most effective strategy for combating this disease is through the exploitation of novel and durable resistance genes derived from the relatives of wheat. Rye (<i>Secale cereale</i> L.) has been extensively hybridized with both tetraploid and hexaploid wheats and represents a valuable genetic resource for enhancing resistance and tolerance to both biotic and abiotic stresses. In this study, two novel 1R (1D) substitution lines, R156 and R189, derived from hexaploid triticale lines Yukuri and T4915, respectively, were comprehensively characterized using non-denaturing fluorescence in situ hybridization (ND-FISH) and immunofluorescence. To physically map the 1R-derived powdery mildew resistance gene from Yukuri, 3485 M₁-M₃ plants from the cross between R156 and susceptible wheat cultivar MY11 were studied by ND-FISH using multiple probes. A cytological bin map for Yukuri chromosome 1R was constructed using 105 molecular markers. Resistance evaluation combined with molecular mapping revealed that the novel resistance locus resides in bin 1RS-4, corresponding to the 58.60-109.28 Mb genome region of Lo7 rye chromosome 1R. Thus, these newly developed wheat-rye 1R translocation and deletion lines are expected to serve as valuable genetic resources for breeding powdery mildew resistant wheat cultivars.