Identification and Cloning of a CC-NBS-NBS-LRR Gene as a Candidate of Pm40 by Integrated Analysis of Both the Available Transcriptional Data and Published Linkage Mapping

Wheat powdery mildew, caused by the obligate parasite Blumeria graminis f. sp. tritici, severely reduces wheat yields. Identifying durable and effective genes against wheat powdery mildew and further transferring them into wheat cultivars is important for finally controlling this disease in wheat production. Pm40 has been widely used in wheat breeding programs in Southwest China due to the spectrum and potentially durable resistance to powdery mildew. In the present study, a resistance test demonstrated that Pm40 is still effective against the Bgt race E20. We identified and cloned the TraesCS7B01G164000 with a total length of 4883 bp, including three exons and two introns, and encoded a protein carrying the CC-NBS-NBS-LRR domain in the Pm40-linked region flanked by two EST markers, BF478514 and BF291338, by integrating analysis of gene annotation in wheat reference genome and both sequence and expression difference in available transcriptome data. Two missense mutations were detected at positions 68 and 83 in the CC domain. The results of both cosegregation linkage analysis and qRT-PCR also suggested that TraesCS7B01G164000 was a potential candidate gene of Pm40. This study allowed us to move toward the final successfully clone and apply Pm40 in wheat resistance improvement by gene engineering.