Identification and Mapping of Sources of Resistance to Stem Rust in Spark/Rialto DH Wheat Population

Stem rust, caused by Puccinia graminis f. sp. tritici (Pgt), historically has been one of the most destructive diseases of wheat worldwide. While genetic resistance is the most effective way of controlling the disease, it is dependent on the discovery and characterisation of novel genes, which can be utilised by breeders. To characterize stem rust resistance, a doubled-haploid (DH) population (Spark/Rialto) was screened for response to Pgt in the greenhouse and field. Seedling tests indicated the involvement of seedling genes Sr5 and Sr31. Field tests indicated the involvement of 3 APR genes over three years. Composite interval mapping of field data with 281 markers revealed major involvement of consistent QTLs on chromosome 1BS, 3BS and 5A for stem rust across experiments, closely associated with the SSR marker gwm18, gwm1034 and gwm443 respectively across experiments. The QTL on 1BS chromosome was contributed by the resistant parent ‘Rialto’ while 3BS and 5A QTLs were contributed by the moderately susceptible parent ‘Spark’. With the absence of Sr31-virulent pathotype in field, the QTL detected on 1BS was associated with the seedling gene Sr31. The QTL identified on 3B may be linked with a leaf rust APR gene detected on chromosome 3BS in the same region (Getie et al. unpublished). QTLs 3BS and 5A with minor and additive effects could be useful for developing varieties with diversified and durable resistance to Pgt.