Virulence And DNA Polymorphism Of Puccinia Striiformis F. Sp. Tritici In Yunnan, Guizhou And Sichuan Province

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the most destructive diseases of wheat worldwide. The most destructive epidemics of stripe rust has historically occurred many times in China and caused seriously yield loss. There exist similar wheat cultivation and climatic condition in the adjacent Yunnan, Guizhou and Sichuan provinces, and stripe rust occurred in this region frequently and the pathogens evolved rapidly compared with other wheat growing regions, such as Huang-Huai-Hai region in China. Therefore, understanding the virulence structure, molecular polymorphism and phylogenetic relationship of wheat stripe rust pathogens among the three provinces described above is important for forecasting and improving prevention and control capabilities of the disease.Based on the gene-for-gene theory, we employed 37 near iso-genic lines (NILs) differentials or known yellow rust resistance (Yr) gene lines to pathotyping 61 stripe rust isolates from Yunnan, Guizhou and Sichuan provinces. Six primer pairs of amplified fragment length polymorphism (AFLP) markers and 6 primer pairs of simple sequence repeat (SSR) markers have been utilized for molecular polymorphism and phylogeny of 120 isolates from these three provinces. The results showed that, all of the pathogens tested possess stable and high frequency of virulences to most of the current known Yr genes. In detail, virulences to Yr5, Yr10+YrMoro, Yr24/Yr26 have not been found and virulence frequencies of Yr9, Yr12, Yrcle were lower than 40%. The virulence profiles of the 61 stipe rust isolates were tested and virulence structure was analysed by cluster analysis using NTSYSpc. The results showed that there existed high similarity about virulence between isolates, and the similarity coefficient was from 0.55 to 1. Among the three provinces, the stripe rust pathogens from Sichuan possess the widest virulence spectrum, and Yunnan and Guizhou ranked after it.The complete set of 18 SSR bands (9 polymorphic) and of 50-76 AFLP bands (20 polymorphic) were separately analyzed by cluster analysis using NTSYSpc.The clustered results showed that similarity coefficient of SSR was from 0.51 to 1.00, and it was 0.46-1.00 for AFLP, which indicated that distinct polymorphism was found among stripe rust pathogens from three provinces. The data of high virulence frequencies and DNA polymorphisms among tested isolates gave evidence for interprovince dispersal events in the past. The low association between virulence and SSR (correlation coefficient 0.07812) or AFLP (correlation coefficient 0.10217) patterns was found.