Abstract: 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.(Author for correspondence.Tel：(0) 25 8439 6026； Fax：(0) 25 8439 5344； E-mail:pdchen@njau.edu.cn)

Key words: chromosome assignment, molecular marker, suppression subtractive hybridization (SSH), Ta-LRR2, Triticum aestivum-Haynaldia villosa 6VS/6AL translocation line.