Mapping a Resistance Gene to Puccinia graminis f. sp. tritici in the Bread Wheat Cultivar 'Matlabas'

Puccinia graminis f. sp. tritici race TTKSF+ was collected from the South African wheat cultivar 'Matlabas' in 2010. F-2 and F-3 populations derived from a Matlabas x Line 37-07 cross segregated for a single resistance gene to race TTKSF that is avirulent to Matlabas. In screening genomic DNA bulks of susceptible or resistant F-2 plants with simple sequence repeat (SSR) markers, three chromosome arm 2BS markers and one multilocus marker amplified alleles present only in the resistant bulks and Matlabas. Additional 2B-specific SSR markers, incorporating markers spanning regions containing Sr9h, SrWLR, Sr28, and Sr47, were screened in the parental lines and mapped in the F-2 population. Linkage and QTL mapping showed that the gene is located between XbarcI60 in the centromeric region and Xgwm47 on the long arm of chromosome 2B. When 2B-specific SNP markers were mapped, the area of interest was delimited to a 15.3 cM region on chromosome arm 2BL, with XIWA543-HRM and Xgwm47 as flanking loci. Matlabas, Webster, and related Sr9h lines all produced a similar, low infection type to race TTKSF, but were susceptible to race TTKSF+. Phenotypic data and allelic studies suggested that stem rust resistance in Matlabas was derived from an Sr9h source.