ARS | Publication request: Genetic Structure of Mycosphaerella Graminicola Populations in the Major Wheat-Growing Regions of the United States

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: May 20, 2010
Publication Date: June 6, 2010
Citation: Gurung, S., Goodwin, S.B., Kabbage, M., Bockus, W., Adhikari, T.B. 2010. Genetic Structure of Mycosphaerella Graminicola Populations in the Major Wheat-Growing Regions of the United States. Phytopathology.

Technical Abstract: Septoria tritici blotch (STB), caused by Mycosphaerella graminicola, is one of the major diseases of wheat worldwide. However, there is little information available on the population genetic structure of this pathogen in the major wheat-growing regions of the United States. We analyzed the genetic structure of 334 isolates of M. graminicola from 11 populations, three from spring wheat in California and North Dakota and eight from winter wheat in Indiana and Kansas using 17 microsatellite markers and two mating type loci. Clone-corrected data revealed that most of the M. graminicola populations had high levels of gene diversity (H = 0.31 to 0.52) and genotype diversity (GD = 0.98 to 1). Both the gene (H) and genotype diversity (GD) was higher for both populations from Indiana and North Dakota than California and Kansas. Similarly, there was a high level of gene flow (Nm = 1.73 to 23.30) and very less genetic distance (D= 0.52 to 0.98) among populations. Equal frequencies of mating types (MAT1-1 and MAT1-2) were found in all populations except in the California population. No evidence of linkage disequilibrium (LD) was observed in all populations analyzed. Overall, these results suggest that there is frequent sexual recombination in the M. graminicola populations and the populations are likely a single large population of M. graminicola affecting wheat fields in the United States.