ARS | Publication request: Physiologic Specialization of Puccinia triticina on Wheat in the United States in 2007

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 16, 2009
Publication Date: April 7, 2009
Repository URL: http://hdl.handle.net/10113/33712
Citation: Kolmer, J.A., Long, D.L., Hughes, M.E. 2009. Physiologic Specialization of Puccinia triticina on Wheat in the United States in 2007. Plant Disease. 98:538-544.

Interpretive Summary: Wheat is attacked by the rust fungus called Puccinia triticina, which causes the disease wheat leaf rust. In 2007 leaf rust was widespread and severe in the Great Plains region, casusing a 14% loss in wheat in Kansas. There are many different forms of the wheat leaf rust fungus that vary in their ability to attack different resistance genes in wheat. Every year the USDA-ARS Cereal Disease Laboratory makes collections of wheat leaf rust from the major wheat growing regions of the United States to determine which forms of the leaf rust fungus are present. In 2007, 52 different forms of the leaf rust fungus were found in the United States. The forms with virulence to leaf rust resistance gene Lr24 were widespread and very common in 2007. Leaf rust types with virulence to genes Lr17, Lr9, and Lr41 were also common in the Great Plains region, and forms with virulence to genes Lr11, Lr18, and Lr26 were common in the southeast states. Leaf rust types with virulence to Lr16 were most common in the spring wheat area of Minnesota and North Dakota and South Dakota. These results can be used by wheat breeders and plant pathologists to help develop wheat cultivars that are very resistant to the leaf rust disease.

Technical Abstract: In 2007 leaf rust of wheat was severe throughout the Great Plains region of North America. Yield losses in wheat due to leaf rust were estimated to be 14% in Kansas. Collections of Puccinia triticina were obtained from rust-infected leaves provided by cooperators throughout the United States and from surveys of wheat fields and nurseries in the Great Plains, Ohio River Valley, southeast, California, and Washington State in order to determine the virulence of the wheat leaf rust population in 2007. Single uredinial isolates (868 in total) were derived from the collections and tested for virulence phenotype on lines of Thatcher wheat that are near-isogenic for leaf rust resistance genes Lr1, Lr2a, Lr2c, Lr3a, Lr9, Lr16, Lr24, Lr26, Lr3ka, Lr11, Lr17a, Lr30, LrB, Lr10, Lr14a, Lr18, Lr21, Lr28, and winter wheat lines with genes Lr41 and Lr42. In the United States in 2007, 52 virulence phenotypes were found. Virulence phenotypes TDBJG, MFPSC, and TDBJH were among the four most common phenotypes and were all virulent to resistance gene Lr24. These phenotypes were found throughout the Great Plains region. Phenotype MLDSD with virulence to Lr9, Lr17, and Lr41 was also widely distributed in the Great Plains. In the soft red winter wheat region of the southeastern states, phenotypes TCRKG with virulence to genes Lr11, Lr26, and Lr18, and MFGJH with virulence to Lr24, Lr26, and Lr11 were among the common phenotypes. Virulence phenotypes with virulence to Lr16 were most frequent in the spring wheat region of the northern Great Plains. Virulence phenotypes with virulence to Lr11, Lr18, and Lr26 were most common in the soft red winter areas of the southeastern states and Ohio Valley. Virulence to Lr21 was not found in any of the tested isolates.