|Kolmer, James - Jim|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2008
Publication Date: 7/1/2008
Citation: Kolmer, J.A., Long, D.L., Hughes, M.E. 2008. Physiologic Specialization of Puccinia triticina on Wheat in the United States in 2006. Plant Disease. 92:1241-1246.
Interpretive Summary: Wheat is attacked by the rust fungus called Puccinia triticina, which causes the disease wheat leaf rust. 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 2006, 56 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 2006. 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. 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: 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 2006. Single uredinial isolates (718 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 2006 56 virulence phenotypes were found. Virulence phenotypes TDBJG, TDBGG, 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 Lr41was also widely distributed in the Great Plains. In the soft red winter wheat region of the southeastern states, phenotypes TCRKG and MBRKG with virulence to genes Lr11, Lr26, and Lr18 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 to Lr21 was not found in any of the tested isolates.