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Title: Virulence and molecular comparison of Puccinia striiformis f. sp. tritici populations in China and the United States

Author
item ZHAN, GANGMING - Washington State University
item Chen, Xianming
item KANG, ZHENSHENG - Northwest Agriculture And Forestry University
item HUANG, LILI - Northwest Agriculture And Forestry University
item WANG, MEINAN - Washington State University
item WAN, ANMIN - Washington State University
item CHENG, PENG - Washington State University
item CAO, SHIQIN - Gansu Agricultural Uiversity
item JIN, SHELIN - Gansu Agricultural Uiversity

Submitted to: Fungal Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/2012
Publication Date: 5/30/2012
Citation: Zhan, G., Chen, X., Kang, Z., Huang, L., Wang, M., Wan, A., Cheng, P., Cao, S., Jin, S. 2012. Virulence and molecular comparison of Puccinia striiformis f. sp. tritici populations in China and the United States. Fungal Biology. 116:643-653.

Interpretive Summary: Stripe rust of wheat is one of the most important diseases in both China and the United States. The Chinese and U.S. populations of the stripe rust fungus were compared for their virulence patterns on wheat cultivars used to differentiate races of the pathogen in China and the U.S. and their genotypes using molecular markers. From 86 Chinese isolates, 54 races were identified based on reactions on the 17 Chinese differentials and 52 races were identified based on the 20 U.S. differentials. The selected 51 U.S. isolates, representing 50 races based on the U.S. differentials, were identified as 41 races using the Chinese differentials. A total of 132 virulence patterns were identified from the 137 isolates based on their reactions on both Chinese and U.S. differentials. Common and unique virulences were identified for both Chinese and U.S. popularions. From the 137 isolates, molecular markers identified 102 genotypes, of which 71 from the Chinese isolates and 31 from the U.S. isolates. The Chinese and U.S. isolates were classified into 20 virulence groups and 18 molecular groups. The Chinese and U.S. populations had similar levels of diversity. Phylogenetic analyses suggested that the Chinese and U.S. populations evolved independently, but may share the same origin. The results support the previous hypothesis that the stripe rust pathogen in the U.S. may be originally from Asia. The results are useful in using effective resistance genes and race non-specific resistance to control the disease in both countries.

Technical Abstract: Stripe rust (yellow rust) of wheat, caused by Puccinia striiformis f. sp. tritici, is one of the most important diseases in both China and the United States. The Chinese and U.S. populations of the stripe rust fungus were compared for their virulence patterns on wheat cultivars used to differentiate races of the pathogen in China and the U.S. and their genotypes using simple sequence repeat (SSR) markers. From 86 Chinese isolates, 54 races were identified based on reactions on the 17 Chinese differentials and 52 races were identified based on the 20 U.S. differentials. The selected 51 U.S. isolates, representing 50 races based on the U.S. differentials, were identified as 41 races using the Chinese differentials. A total of 132 virulence patterns were identified from the 137 isolates based on their reactions on both Chinese and U.S. differentials. Although few Chinese and U.S. isolates had the same virulence patterns on the Chinese or the U.S. differentials, none of the isolates from the two countries had identical virulence patterns on both sets of differentials. From the 137 isolates, SSR markers identified 102 genotypes, of which 71 from the Chinese isolates and 31 from the U.S. isolates. Using the middle value of the similarity range, the virulence data clustered the 137 isolates into 20 virulence groups and the marker data clustered the isolates into 18 molecular groups. Virulence and SSR data had a low (r = 0.38), but significant (P = 0.01) correlation. The Chinese and U.S. populations had similar levels of diversity based on Kosman index values. Principal component analysis using the SSR data separated the two populations more clearly than using the virulence data. A non-rooted tree generated using the molecular data suggested that the Chinese and U.S. populations evolved independently, but may share the same origin, which also indicated by significant gene flow. The results support the previous hypothesis that the stripe rust pathogen in the U.S. may be originally from Asia.