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Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/31/2005 Publication Date: 10/1/2005 Citation: Jin, Y. 2005. Races of Puccinia graminis in the United States during 2003. Plant Disease. 89:1125-1127. Interpretive Summary: Stem rust of small grain cereals, caused by the fungus Puccinia graminis, is a major disease of wheat, barley and oat. Significant losses occurred in the past when the disease developed into epidemic proportions in small grain crops. The use of effective resistance in major cereal production regions has brought the disease under control. Race surveys, commenced annually throughout major cereal producing states in the United States and Prairie Provinces of Canada, yield information on the types and degrees of variations in the pathogen population and changes over time. This information, in turn, is used to guide the utilization of stem rust resistance genes in crop improvement. In 2003, races of the stem rust pathogen from barberry, wheat, barley, and oats were surveyed across the United States. Stem rust of wheat and oats was not identified from barberry. The most common wheat stem rust race (QFCS) identified from the survey was also found in previous surveys and it has limited virulence towards wheat cultivars growing in the United States. Several hard red winter and soft wheats, including Thunderbolt, Onaga, Ankor, Nufrontier, Lakin, Truman, Roane, and Additions, however, were found to be susceptible to this race. A race (TTTT), first found in 2000, was identified again in 2003. This race possesses virulence to many resistance genes present in the US wheat varieties and should be targeted in the development of resistant cultivars. Races of the oat stem rust found in this survey were similar to those identified in the previous surveys. Technical Abstract: Races of Puccinia graminis from barberry, wheat, barley, and oat were surveyed across the United States during the 2003 crop season. Aecial infections on barberry were primarily P. graminis f. sp. secalis, and inoculation using aeciospores failed to produce infection on wheat and oat. Race QFCS of P. graminis f. sp. tritici was the most common race identified from wheat and barley. Race QFCS has virulence on stem rust resistance genes Sr5, 8a, 9a, 9d, 9g, 10, 17, and 21 that are used in the differentials for race identification. Several hard red winter and soft wheats were found to be susceptible to QFCS based on seedling tests, including Thunderbolt, Onaga, Ankor, Nufrontier, Lakin, Truman, Roane, and Additions. Race TTTT, first identified from a collection in Texas in 2000 and Minnesota in 2001, was identified again from a sample collected from Texas in 2003. This race possesses virulence to all the 16 Sr genes present in the wheat stem rust differentials and should be targeted in breeding for stem rust resistance. Race QFCN, collected from barley, appeared to be a new race in the North American stem rust population. Races QCCJ and MCCF were identified, but with low frequency. Three races, NA-27, NA-29 and NA-67 of P. graminis f. sp. avena, composed of the majority of stem rust collections from oats and wild oats. Other oat stem rust races identified in 2003 included NA-5, NA-10, and NA-30. Race NA-76, similar to NA-67 but avirulent on Pg15, was identified for the first time in the United States. |
