Submitted to: Cereal Rusts and Mildews Conference European and Mediterranean Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2004
Publication Date: 7/1/2004
Citation: Markell, S.G., Milus, E.A., Chen, X. 2004. Genetic diversity of puccinia striiformis f. sp. tritici in the united states. 11th International Cereal Rusts and Mildews Conference European and Mediterranean Proceedings. Page A2.43.
Technical Abstract: In North America, epidemics of stripe rust, caused by Puccinia striiformis f. sp. tritici, historically have occurred in several regions of Mexico, and in western United States (Washington, Oregon, Idaho, California). Since 2000, stripe rust has emerged as a severe disease in south-central states (Arkansas, Louisiana, Texas) and in the Great Plains (Oklahoma, Kansas, Nebraska, Colorado). Recent epidemics in the south-central states and the Great Plains have been attributed to widespread and consistent overwintering of the pathogen in south-central states, favorable weather, susceptible cultivars, and new races that overcome resistance gene Yr9 that had been effective against all races until 2000. The pathogen has no known sexual stage or alternate host to aid survival between wheat crops, and environmental conditions in the south-central states and Great Plains are not favorable for survival of the uredial stage over summer. The source of inoculum that overwinters in south-central states and the mechanism for evolving new races of the pathogen are not determined. Until recently, virulence/avirulence on differential lines was the only type of marker available to track inoculum dispersal and to determine how new races evolve. Polymorphic AFLP (Justesen et al., 2002) and SSR (Enjalbert et al., 2002) markers for P. striiformis f. sp. tritici were identified recently and may be useful in epidemiology and genetic studies of the pathogen. The objective of this study was to determine if the AFLP and SSR markers were useful for differentiating US isolates and to identify additional polymorphic markers. For each isolate, each polymorphism was scored as present or absent, and the data were analyzed with the Numerical Taxonomy System-pc. Both AFLP and SSR markers clearly distinguished pre-2000 isolates from isolates collected in 2000 and later. These molecular markers likely would be useful for understanding genetic relationships among isolates, migration patterns among regions that may serve as donors or recipients of inoculum in North America, and determining the mechanism for the evolution of new races.