Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2012
Publication Date: 3/10/2012
Citation: Liu, Z.H., Zhong, S., Stasko, A.K., Edwards, M.C., Friesen, T.L. 2012. Virulence profile and genetic structure of a North Dakota population of Pyrenophora teres f. teres, the causal agent of net form net blotch of barley. Phytopathology. 102:539-546. Interpretive Summary: The ascomycete Pyrenophora teres is the causal agent of net blotch of barley, a very common foliar disease in most barley-growing regions worldwide. In this study, we collected P. teres f. teres isolates over four growing seasons from two North Dakota barley growing regions varying in environmental conditions. Using the collected isolates, we assessed the virulence structure using a set of 22 barley differential lines. Additionally, we evaluated the genetic diversity in the collection, and compared the similarity among different populations across two locations and multiple years. The objective of this study was to identify effective resistance sources, determine the genetic variation between and within populations from the two locations and test the hypothesis of random mating within the North Dakota populations.
Technical Abstract: To monitor dynamic changes of a Pyrenophora teres f. teres population in North Dakota, we collected fungal isolates annually during 2004 to 2007 from North Dakota State University agricultural experiment stations at Fargo and Langdon. Up to 10 isolates for each year and each location were randomly selected and subjected to analysis for virulence variation by inoculation onto 22 barley differential lines and for genetic differentiation using 13 SSR markers that were randomly distributed in the genome. Pathogencity tests revealed a total of 49 pathotypes from 75 isolates indicating a wide range of pathogenic diversity. Two-way ANOVA with disease ratings showed a significant difference in the virulence among isolates, and in the resistance among barley lines as well as the interactions between the two. ‘CI5791’, ‘Algerian’ and ‘Heartland’ were three barley lines showing a high level of resistance to all ND isolates tested; however many previously reported resistance genes have been overcome. In population genetic analysis, Langdon isolates showed a slightly higher allelic and genotype diversity than Fargo isolates. A Nei’s Gst value of 0.076 was obtained when we compared the two populations pooled by location suggesting that approximately 93 % of the total genetic variability exists within the populations rather than between. A linkage disequilibrium test with isolates without redundant genotypes provided little evidence of nonrandom association between SSR loci, which agrees with a previous study. Our results suggest the populations from the two locations are derived from a common source and undergo frequent recombination. This research provides important information for barley breeders in North Dakota regarding breeding and deployment of net form net botch resistant cultivars.