Development and comparative genomic mapping of Dasypyrum villosum 6V#4S-specific PCR markers using transcriptome data.

Twenty-five Dasypyrum villosum 6V#4S-specific PCR markers were developed using transcriptome data and further assigned to comparative genomic maps of wheat chromosome 6A, 6B, and 6D and barley chromosome 6H contrasting their homologous genes in these genomes. Two Dasypyrum villosum accessions, D.v#2 and No. 1026 from England and Russia, respectively, contain Pm21 on chromosome 6V#2S and PmV on chromosome 6V#4S. Both genes confer high resistance to powdery mildew (PM) in wheat. Even though several molecular markers have been developed to detect Pm21 and PmV, only the MBH1 marker can simultaneously detect both Pm21 and PmV. In this study, we first used a high-throughput sequencing technique to obtain the transcriptome sequences of a wheat-D. villosum translocation line, Pm97033-which contains chromosome 6V#4S carrying the PmV locus, under wheat PM pathogen induction. Twenty-five 6V#4S chromosome-specific markers were developed. Three of them were able to clearly distinguish chromosomes 6V#4S and 6V#2S by product size, four amplified the product specific for chromosome 6V#4S only, and the remaining 18 markers identified chromosome 6VS in wheat backgrounds. Two different D. villosum accessions, their derived translocation lines and wheat varieties carrying different chromosome 6VS were identified using these specific markers. The 25 newly developed markers together with the known PM resistance gene Stpk-V were used to construct comparative genomic maps with the homoeologous chromosome arms of wheat and barley. The colinearity of the identified gene sequences amplified by the 25 markers among wheat chromosomes 6A, 6B, and 6D and barley chromosome 6H was not very conserved and interrupted frequently by inversion and insertion. Our markers have potential in marker assisted selection for PM resistance breeding, and for locating other potential important genes and cloning the PmV gene on chromosome 6V#4S.