Virulence characterization of Puccinia striiformis f. sp. tritici using a new set of Yr single-gene line differentials in the United States in 2010

Authors: WAN, ANMIN - Washington State University; Chen, Xianming

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2014
Publication Date: 11/1/2014
Citation: Wan, A., Chen, X. 2014. Virulence characterization of Puccinia striiformis f. sp. tritici using a new set of Yr single-gene line differentials in the United States in 2010. Plant Disease. 98(11):1534-1542.

Interpretive Summary: The wheat stripe rust and barley stripe rust pathogens are highly The wheat stripe rust and barley stripe rust pathogens are highly variable in virulence. Both forms can cause huge yield loss of their host crops when susceptible cultivars are grown and the weather conditions are favorable for stripe rust. Monitoring and characterization of virulences in the pathogen populations are crucial for control of stripe rust. This paper documents the most widespread and damaging stripe rust epidemic in the recorded history in the U.S., establishes a new system for identification of races of the wheat stripe rust pathogen, and reports races of wheta and stripe rust pathogens and their distribution and frequences. 41 wheat stripe rust races and 6 barley stripe rust races were identified. Wheat stripe rust races idenitfied with the new race identification system provide direct information of virulence to particular resistance genes and the race information should be more useful for developing resistant cultivars and the disease management.

Technical Abstract: Puccinia striiformis f. sp. tritici (Pst) causing stripe rust of wheat, and P. striiformis f. sp. hordei (Psh) causing stripe rust of barley, are highly variable in virulence. Both formae speciales can cause huge yield loss of their host crops when susceptible cultivars are grown and the weather conditions are favorable for stripe rust. Monitoring and characterization of virulences in the pathogen populations are crucial for control of stripe rust. In 2010, stripe rust of wheat was the most widespread in the recorded history in the U.S., resulting in large-scale application of fungicides and substantial yield loss. Although not comparable to stripe rust of wheat in scale and damage level, stripe rust of barley occurred in California, Oregon, Washington, Idaho, Utah, Montana, and North Dakota. A total of 412 stripe rust samples were collected from 24 states. A new set of 18 Yr (yellow rust) single-gene lines were used to differentiate Pst races and 12 barley cultivars were used to identify Psh races. From the 348 viable Pst and 30 Psh isolates obtained from the 412 samples, 41 Pst races, named PSTv-1 to PSTv-41 to distinguish from previously reported PST races, and 6 Psh races were identified. An octal system was used to describe the virulence/avirulence patterns of the PSTv races. The virulence spectra of the Pst races ranged from 0 to 13 of the 18 genes. The top five most predominant PSTv races were PSTv-37 (34.5%); PSTv-11 (17.5%); PSTv-14 (7.2%); PSTv-36 (5.2%); and PSTv-34 (4.9%). No races had virulence to Yr5 and Yr15, and therefore, these two genes are still effective against all races identified in the U.S. Based on the virulence data, the 41 PSTv races were clustered into two major groups. Six Psh races (PSH-33, PSH-46, PSH-48, PSH-52, PSH-54, and PSH-81) were identified with PSH-33 (virulent on barley differentials 1 and 7) as the most predominant one (47%).