Physiologic specialization of Puccinia triticina on wheat in the United States in 2013

Authors: Kolmer, James; Hughes, Mark

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2015
Publication Date: 9/1/2015
Citation: Kolmer, J.A., Hughes, M.E. 2015. Physiologic specialization of Puccinia triticina on wheat in the United States in 2013. Plant Disease. 99:1261-1267.

Interpretive Summary: Wheat is attacked by Puccinia triticina, which causes the disease wheat leaf rust. There are many different forms or races 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 the wheat leaf rust fungus from the major wheat growing regions of the United States to determine which forms of P. triticina are present. In 2013, 79 different forms of the leaf rust fungus were found in the United States. The forms with virulence to the resistance genes in the commonly grown hard red winter wheats were widespread throughout the eastern states and the Great Plains region. The races with virulence to the genes present in the soft red winter wheats were found in the eastern states and the Ohio Valley region. The most commonly grown hard red winter wheat cultivars and soft red winter wheat cultivars are susceptible to the most common leaf rust races found in the regions where these wheat cultivars are grown. It will be important to develop wheat cultivars with new combinations of leaf rust resistance genes in the winter wheat regions. The results from the annual virulence survey are 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 wheat fields and breeding plots by USDA-ARS personnel and cooperators in the Great Plains, Ohio River Valley, and southeastern states in order to determine the virulence of the wheat leaf rust population in 2013. Single uredinial isolates (490 total) were derived from the collections and tested for virulence phenotype on 20 lines of Thatcher wheat that are near-isogenic for leaf rust resistance genes. In 2013, 79 virulence phenotypes were described in the United States. Virulence phenotypes MBTNB, TNBGJ and MCTNB were the three most common phenotypes. Phenotypes MBTNB and MCTNB are both virulent to Lr11, and MCTNB is virulent to Lr26. MBTNB and MCTNB were most common in the soft red winter wheat region of the southeastern states and Ohio Valley. Phenotype TNBGJ is virulent to Lr39/41 and was widely distributed throughout the hard red winter wheat region of the Great Plains. Isolates with virulence to Lr11, Lr18, and Lr26 were most common in the southeastern states and Ohio Valley region. Isolates with virulence to Lr21, Lr24, and Lr39/41 were most common in the hard red wheat region of the southern and northern Great Plains.