Development of an STS Marker Linked to Powdery Mildew Resistance Genes PmLK906 and Pm4a by Gene Chip Hybridization

Wheat (Triticum aestivum L.) line Lankao 90(6) carries a recessive powdery mildew resistance gene temporarily named PmLK906 on chromosome 2AL. Near PmLK906 there is another known powdery mildew resistance gene locus Pm4. To track the two powdery mildew resistance genes in wheat breeding program by marker assisted selection (MAS), a linked molecular marker was developed in this study. Wheat gene chip hybridization combined with bulked segregant analysis (BSA) was used to develop an sequence-tagged sites (STS) marker for PmLK906 and Pm4. A new 2 125 bp full-length cDNA clone (GenBank accession no. EU082094) similar to csAtPR5 of Aegilops tauschii was isolated from Lankao 90(6) 21-12, and temporarily named TaAetPR5. Specific products could be amplified from cultivars or lines possessing Pm4a, Pm4b and PmLK906 with primers p9-7p1 and p9-7p2 derived from TaAetPR5. TaAetPR5 was linked to PmLK906 at a genetic distance of 7.62 cM, and cosegregated with Pm4a. The p9-7p1 and p9-7p2 could be used as an STS marker for these resistance genes in wheat breeding. Because this marker was cosegregated with Pm4a, it can be used in map-based cloning of the alleles atPm4 locus also.