| Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici(Pst), is one of the main important fungal diseases in wheat, which has caused great losses to the wheat production in the world. China is the largest epidemic area for wheat stripe rust. The breeding and applying rust-resistant cultivars has been considered as the most effective and economical strategy for the prevention and control of yellow rust. However, the resistance breakdown of wheat cultivars is very serious due to the occurrence and development of new virulent races. Being an obligate fungus, the race identification and monitoring of Pst were complicated and time-consuming, which have severely restricted the population genetic structure and biology study on Pst.Microsatellite-anchored fragment length polymorphism(MFLP), is a PCR-based method for DNA fingerprinting, which combines the concept of amplified fragment length polymorphism and microsatellite-anchor primer technique. The MFLP reaction system special for the obligated pathogens, wheat rust fungi, was established successfully in this research. The genetic diversity of 73 isolates of wheat stripe rust collected from Yunnan, Guizhou, Sichuan and Gansu province was analyzed using MFLP method for the first time, and the main results derived from this research were as follows.1. Using mixed urediniospores of wheat yellow rust, several main factors such as the genomic DNA preparation, enzyme digestion and PCR amplification, which might influence the final MFLP result were studied and optimized in this research. The MFLP reaction system for wheat stipe rust was successfully established.2. 13 pair primers, which could produce bands with high quality and high polymorphism, were selected out of 456 pair primers. 42 polymorphic bands were detected in the experimental materials with 13 pair MFLP primers.3. 73 isolates of Pst collected from Yunnan, Guizhou, Sichuan and Gansu province were analyzed with MFLP-clustering method. The basic value of similarity coefficient (SIM)was 0.46. All the isolates could be divided into two groups at SIM 0.60, neither of the two groups was the predominant one. The MFLP-clustering result of Pst collected from the areas above-mentioned was not related with the the geographic areas.Taking the main factors such as climate, geographical location and wheat varieties into account, we can't draw a clear conclusion whether the stripe rust pathogen is able to exchange between Gansu and Sichuan, especially between Gansu and Yunnan, Guizhou.4. 27 isolates of Pst collected from Yunnan, Guizhou and Sichuan province were also analyzed, and the basic value of SIM was 0.43. At SIM 0.61, the isolates could be divided into two groups, the first group consisted of 11 isolates from Yunnan and Guizhou, 2 isolates from Sichuan; There were 11 isolates from Sichuan, 3 isolates from Yunnan and Guizhou in the second group. According to the MFLP-clustering result, we can initially speculated that there was a certain level of genetic diversity, and also pathogen exchange exist between Sichuan, Yunnan and Guizhou province.5. The Gansu Pst population also consisted of two groups, which belonged to Group A and B respectively, each group included 23 isolates. The sub-group constitution was different between Tao-Min-middle Gansu area and the upper reaches of Weihe river basin, which may be ascribed to the increasing of pathotypes of wheat stripe rust virulent to Suwon 11, especially for CYR33. The MFLP-clustering result of isolates from Gangu and Wushan counties of Gansu province showed that the pathogen exchange was undergone frequently within the two areas.
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