Race and Virulence Analysis of Puccinia triticina in China in 2014 and 2015.

Wheat leaf rust, caused by Puccinia triticina, is an important fungal disease of wheat in China. To study races of the pathogen in China, leaf rust samples were collected from 14 provinces in 2014 and 15 provinces in 2015. From the samples, 494 single-uredinial isolates were derived from the 2014 collection and 649 from the 2015 collection. These isolates were tested on 40 near-isogenic lines of Thatcher carrying single leaf rust resistance genes. From the isolates, 84 races were identified in 2014 and 65 races in 2015. Races THTT (22.1%), THTS (19.6%), THJT (8.7%), PHTT (4.9%), and PHJT (3.6%) were the most common races in 2014, and THTT (28.4%), THTS (12.8%), THJT (11.6%), THJS (9.9%), and PHTT (9.7%) were the most frequent in 2015. All of these races were avirulent to resistance genes Lr9 and Lr24. THTT and THTS, the most frequent races in both years, were widely distributed throughout the country. The frequencies of isolates with virulence to Lr1, Lr2a, Lr2c, Lr3, Lr16, Lr26, Lr11, Lr17, LrB, Lr10, Lr14a, Lr2b, Lr3bg, Lr14b, Lr32, Lr33, and Lr50 were over 80%, whereas the frequencies of virulence to Lr9, Lr19, Lr25, Lr28, Lr29, and Lr47 were less than 3.5%. In the present study, all isolates were avirulent to Lr24 and Lr38. The race analysis and individual virulence frequencies provide guidance to breeders in choosing leaf rust resistance genes for use in breeding programs.