Identification and mapping of pm2026: a recessive powdery mildew resistance gene in an einkorn (Triticum monococcum L.) accession.

Triticum monococcum accession TA2026 showed resistance to wheat powdery mildew. To identify the resistance gene and transfer it to common wheat, genetic analysis and molecular mapping were conducted using an F2 population and derived F3 families from the cross of TA2026xM389. The results indicated that TA2026 possessed a recessive powdery mildew resistance gene. This gene was mapped to the terminal portion of chromosome 5AmL and flanked by SSR marker loci Xcfd39 and Xgwm126. Eight RFLP markers previously mapped to the terminal chromosome 5AmL were converted into STS markers. Three loci, detected by MAG1491, MAG1493 and MAG1494, the STS markers derived from RFLP probes CDO1312, PSR164 and PSR1201, respectively, were linked to this resistance gene with Xmag1493 only 0.9 cM apart from it. In addition, the STS marker MAG2170 developed from the tentative consensus wheat cDNA encoding the Mlo-like protein identified a locus co-segregating with Xmag1493. This is the first recessive powdery mildew resistance gene identified on chromosome 5Am, and is temporarily designated pm2026. We have successfully transferred it to a tetraploid background, and this resistance stock will now be used as the bridge parent for its transfer to common wheat.