Mapping of the loose smut resistance gene Ut6 in wheat (Triticum aestivum L.)

Loose smut of wheat (Triticum aestivum L.) caused by Ustilago tritici (Pers.) Rostr. can cause considerable yield losses in the absence of appropriate management practices. The use of wheat varieties with loose smut resistance is an efficient and effective control technique. However, the development of commercial wheat lines with resistance to loose smut is time- and labour-consuming. DNA markers linked to loose smut resistance gene(s) would assist the development of loose smut resistant genotypes. The genetics of loose smut resistance was studied in an F5‐derived recombinant inbred line (RIL) population of 94 lines from the cross BW278/AC Foremost. The line AC Foremost is resistant and line BW278 is susceptible to U. tritici race T10. Phenotypic assessment revealed that a single gene, designated Ut6, segregated for resistance to race T10 in the RIL population. A modified bulked segregant analysis identified a microsatellite marker linked to Ut6. A linkage map was developed consisting of linked microsatellite loci and the resistance gene. The loose smut resistance gene Ut6 mapped to the long arm of chromosome 5B. Five microsatellite markers mapped within 6.7 cM of Ut6. The microsatellite markers gpw5029 and barc232 flanked Ut6 at distances of 1.3 and 2.8 cM on the distal and proximal sides, respectively. A diverse set of wheat lines was haplotyped for Ut6 using the linked microsatellite markers gpw5029 and barc232. The haplotype analysis suggested that the microsatellite markers associated with Ut6 will be useful for marker-assisted selection of loose smut resistant wheat lines.