Genetic mapping of Stb19, a new resistance gene to Zymoseptoria tritici in wheat

Key messageA new and dominant R gene Stb19 is identified from a soft wheat cultivar Lorikeet' and was mapped on the distal region of chromosome 1DS. Two tightly linked KASP markers were also discovered and validated for molecular-assisted breeding programs.AbstractA new R gene, designated as Stb19, provides resistance to Zymoseptoria tritici in wheat. This new dominant gene resides on the short arm of chromosome 1D, exhibiting complete resistance to three Z. tritici isolates, WAI332, WAI251, and WAI161, at the seedling stage. A genetic linkage map, based on an F-2:3 population of Lorikeet' and Summit,' found the Stb19 gene at a 9.3cM region on 1DS, closely linked with two Kompetitive Allele-Specific PCR markers, snp_4909967 and snp_1218021. Further, the two markers were tested and validated in another F-2:3 population and 266 different wheat accessions, which gave over 95% accuracy of resistance/susceptibility prediction. Combined with the physical location of the identified SNPs and the previous evidence of gene order on chromosome 1DS (centromere-Sr45-Sr33-Lr21-telomere), Stb19 is proposed to be located between Sr33 and Lr21. Thus, the newly discovered Stb19 along with the KASP markers represents an increase in genetic resources available for wheat breeding resistance to Z. tritici.