Cloning of a Resistance Gene Analog from Wheat and Development of a Codominant PCR Marker for Pm21.

To investigate the mechanism of resistance to wheat ( Triticum aestivum L.) powdery mildew, suppression subtractive hybridization was conducted between an isogenic resistant line carrying Pm21 and its recurrent parent Yangmai 5 to isolate the resistance relative genes. A cDNA fragment specifically expressed in the resistant line was obtained and its full length was cloned by in silico cloning and RT-PCR. This gene encoded a deduced protein of 219 amino acids with a leucine-rich repeat (LRR) motif, often found in plant resistance genes, and was designated as Ta-LRR2. Ta-LRR2 had an increased expression level in the resistant line after inoculation with Erysiphe graminis DC. f. sp. tritici Marchal. PCR analysis with different cytogenetic stocks suggested that Ta-LRR2 was specifically associated with chromosome arms 6VS and 6AS. Linkage analysis further showed that Ta-LRR2 could be used as a resistance gene analog polymorphism marker of Pm21 for marker-assisted selection in germplasm enhancement and breeding practice. Moreover, how to isolate Pm21 based on the information obtained for Ta-LRR2 is discussed. (Managing editor: Li-Hui Zhao) [ABSTRACT FROM AUTHOR]