Tuesday, November 14, 2006

Development of PCR Markers Specific to Epidemic Strain of Wheat Stripe Rust.

Ya-Jun Xi1, Wen-Sheng Hou2, Xue-Feng Ma3, He-Ping Lu1, and Shu-Dong Liu1. (1) College of Agronomy, Northwest A and F Univ, Yangling, China, (2) Chinese Academy of Agriculture Sciences, South Zhongguancun 12, Beijing, China, (3) Forage Improvement Div, The Samuel Roberts Noble Foundation, Ardmore, OK 73402-2180

Stripe rust is one of the most critical diseases of wheat in the world. At present, the dominant species of the stripe rust in China is ‘Tiaozhong 32’ strain. To develop markers for molecular breeding, an F2 population was created between two lines, ‘Xiaoyan22’, which was susceptible to the strain, and 92R137, which was resistant to the strain. A total of 450 random 10-mer primers were used for bulk analysis of the population. Two primers, S29 and S41, showed polymorphisms between resistant and susceptible lines, where S29 and S41 produced bands S29800 and S41500, respectively, in the susceptible bulk, but not in the resistant bulk.  The results were further confirmed with 30 F2 and F3 individuals, where the two polymorphic bands were consistently re-produced in all susceptible but not resistant plants.  To optimize the primers, the two specific bands were isolated, cloned and sequenced. Based on the sequences, primers SC-29 and SC-41 were designed and synthesized.  Follow up application of the new primers showed stable amplification of specific bands among the individuals susceptible to the stripe rust strain.  The result showed that the SCAR markers SC-29 and SC-41 were converted successfully from the RAPD markers S29800 and S41500 and could be used to screen any potential wheat resources resistant to ‘Tiaozhong 32’ strain. With this method, six wheat materials resistant to ‘Tiaozhong 32’ strain were identified and used for breeding program.