Genetic mapping of the common and dwarf bunt resistance gene Bt12 descending from the wheat landrace PI119333

Common bunt (CB), caused by Tilletia caries and T. foetida , and dwarf bunt (DB), caused by T. controversa , are particularly destructive diseases of wheat grown under organic (low-input) production conditions and negatively affect both grain yield and quality. A total of 16 race specific bunt resistance genes have been proposed to date. Thereof, only Bt9 and Bt10 have been mapped so far. A mapping and two validation populations comprising 176 recombinant inbred lines were evaluated for CB and DB in artificially inoculated field trials. The mapping population was derived from the cross of the Bt12 carrier PI119333 and the susceptible cultivar ‘Rainer’. The population was genotyped with the Illumina 15 K SNP chip and the major QTL QBt.ifa-7DS representing Bt12 was identified on chromosome 7DS, explaining 39% and 14% of the phenotypic variation for CB and DB resistance, respectively. Selected SNP markers were turned into Kompetitive Allele-Specific (KASP) markers and used to validate Bt12 in two independent validation populations. These markers can be used for introgressing Bt12 into regionally adapted elite breeding material.