|Kolmer, James - Jim|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/2007
Publication Date: 7/7/2007
Citation: Kolmer, J.A., Long, D.L., Hughes, M.E. 2007. Physiologic Specialization of Puccinia triticina on Wheat in the United States in 2005. Plant Disease. 91:979-984. Interpretive Summary: Collections of the rust fungus Puccinia triticina, that is the cause of the leaf rust disease on wheat, were obtained from the major wheat growing regions of the U.S. in 2005. The collections of the leaf rust fungus were purified on seedlings of wheat plants in greenhouses, and were then tested for their ability to attack 16 different types of wheat, that each have a different gene that gives resistance to the leaf rust fungus. From the many collections (797) that were tested on the wheat lines, 72 different types of leaf rust (physiologic races) were described in the U.S. in 2005. Different races of leaf rust were found in the southeastern states and the Ohio Valley areas where soft red winter wheats are grown, compared with races that were found in the southern and northern Great Plains region of the U.S where hard red winter and spring wheats, respectively are grown. The leaf rust races differ in their ability to attack the different types of wheat cultivars that are grown in the U.S., which has lead to the different wheat growing areas of the U.S. having different leaf rust races. The results from this study can be used by wheat breeders and plant pathologists to determine which leaf rust resistance genes can be added to wheat breeding programs in order to develop wheat cultivars with good resistance to the many different races of the leaf rust fungus.
Technical Abstract: Collections of Puccinia triticina were obtained from rust infected wheat leaves by cooperators throughout the United States and from surveys of wheat fields and nurseries in the Great Plains, Ohio Valley, southeast, California, and the Pacific Northwest, in order to determine the virulence of the wheat leaf rust population in 2005. Single uredinial isolates (797 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 2005, 72 virulence phenotypes of P. triticina were found. Virulence phenotype TDBGH selected by virulence to resistance gene Lr24, was the most common phenotype in the United States, and was found throughout the Great Plains region. Virulence phenotype MCDSB with virulence to Lr17a, and Lr26, was the second most common phenotype and was found widely in the wheat growing regions of the United States. Virulence phenotype MFPSC, which has virulence to Lr17a, Lr24, and Lr26, was the third most common phenotype, and was found in the Oho Valley region, the Great Plains and California. The highly diverse population of P. trticina in the U.S. will continue to present a challenge for the development of wheat cultivars with effective durable resistance to leaf rust.