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Title: Emerging Yr26-virulent races of Puccinia striiformis f. sp. tritici are threatening the wheat production in the Sichuan Basin, China

Author
item HAN, D - Northwest Agriculture And Forestry University
item WANG, Q - Northwest Agriculture And Forestry University
item Chen, Xianming
item ZENG, Q - Northwest Agriculture And Forestry University
item WU, J - Northwest Agriculture And Forestry University
item XUE, W - Northwest Agriculture And Forestry University
item ZHAN, G - Northwest Agriculture And Forestry University
item HUANG, L - Northwest Agriculture And Forestry University
item KANG, Z - Northwest Agriculture And Forestry University

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/29/2014
Publication Date: 7/6/2015
Citation: Han, D.J., Wang, Q.L., Chen, X., Zeng, Q.D., Wu, J.H., Xue, W.B., Zhan, G.M., Huang, L.L., Kang, Z.K. 2015. Emerging Yr26-virulent races of Puccinia striiformis f. sp. tritici are threatening the wheat production in the Sichuan Basin, China. Plant Disease. 99:754-760.

Interpretive Summary: Stripe rust is one of the most destructive diseases of wheat in the world. The Sichuan Basin is one of the most important regions of wheat production and stripe rust epidemics in China. Stripe rust resistance gene Yr26 has been widely used in wheat breeding programs and in many cultivars grown in this region since the gene was discovered in the early 1990s. Virulence to Yr26 has increased in frequency since its first detection in 2008. The objective of this study was to assess the vulnerability of the wheat cultivars and breeding lines in the Sichuan Basin to Yr26-virulent races. A total of 85 wheat accessions were tested with three races not virulent to Yr26 and two races virulent to Yr26. DNA markers for Yr26 were used to determine the presence and absence of Yr26 in the wheat accessions. Of 85 wheat accessions tested, only 5 were resistant and 19 susceptible to all races tested, and the remaining 61 were resistant to at least one or more races tested in seedling stage. Sixty five (76.5%) accessions were susceptible to an emerging Yr26-virulent race. In field tests, susceptible accessions increased from 31.8% in a nursery inoculated with predominant and Yr26-avirulent races to 61.2% in the nursery inoculated with the predominant races mixed with a Yr26-virulent race. Based on the results of the molecular marker and race tests, 33 (38.8%) accessions were determined to have Yr26, showing that the Yr26 virulence is a major threat to wheat production in the Sichuan Basin and potentially in other regions of China.

Technical Abstract: Stripe rust, caused by Puccinia striiformis f. sp. tritici , is one of the most destructive diseases of wheat in the world. The Sichuan Basin is one of the most important regions of wheat production and stripe rust epidemics in China. Stripe rust resistance gene Yr26 (the same gene as Yr24) has been widely used in wheat breeding programs and in many cultivars grown in this region since the gene was discovered in the early 1990s. Virulence to Yr26 has increased in frequency since its first detection in 2008. The objective of this study was to assess the vulnerability of the wheat cultivars and breeding lines in the Sichuan Basin to Yr26-virulent races. A total of 85 wheat accessions were tested with Yr26-avirulent races CYR32, CYR33, and Su11-4 and two Yr26-virulent races V26/CM42 and V26/Gui22. DNA markers for Yr26 were used to determine the presence and absence of Yr26 in the wheat accessions. Of the 85 wheat accessions, only 5 were resistant and 19 susceptible to all races tested, and the remaining 61 were resistant to at least one or more races tested in seedling stage. Sixty five (76.5%) accessions were susceptible to the emerging Yr26-virulent race V26/Gui22. In field tests, susceptible accessions increased from 31.8% in a nursery inoculated with predominant and Yr26-avirulent races to 61.2% in the nursery inoculated with the predominant races mixed with V26/Gui22. Based on the results of the molecular marker and race tests, 33 (38.8%) accessions were determined to have Yr26, showing that the Yr26 virulence is a major threat to wheat production in the Sichuan Basin and potentially in other regions of China.