Physical mapping of a powdery mildew resistance related gene Hv-S/TPK by FISH with a TAC clone in wheat

Powdery mildew, caused by Erysiphe graminis DC.f. sp. Tritic Marchl., is one of the most serious diseases for wheat production worldwide. Pm21 is a broad-spectrum resistance gene to powdery mildew and has been located on the short arm of the chromosome 6V of Haynaldia villosa L (2n=2x=14, VV). In the previous study, a resistance related gene, Hv-S/TPK (serine/threonine protein kinase), has been cloned and showed enhanced resistance to powdery mildew when over-expressed in the transgenic common wheat. A TAC library was constructed using wheat-H.villosa translocation line 6VS/6AL. Screening the library with a gene-based marker specific to the gene Hv-S/TPK identified a positive clone, TAC15. Sequence analysis of TAC15 confirmed that it contained Hv-S/TPK gene. In this study, TAC15 was used to determine the physical location of the Hv-S/TPK gene by sequential fluorescence in situ hybridization (FISH) and genomic in situ hybridization (GISH). The result indicated that TAC15 detected a single locus on 6VS. The FL values of this locus varied between 0.566 to 0.587 when assessed using different genetic stocks including 6Vaddition line, 6V(6A) substitution line and 6VS/6AL translocation lines.