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Population Genetic Analyses of Fusarium asiaticum Populations from Barley Suggest a Recent Shift Favoring 3ADON Producers in Southern China

First, second, fourth, fifth, sixth, and tenth authors: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agriculture Sciences, Beijing 100193, China; third and ninth authors: Plant Research International BV, P.O. Box 16 6700 AA, The Netherlands; and seventh and eighth authors: Institute for Plant Protection and Soil Sciences, Hubei Academy of Agricultural Sciences, 430064, Wuhan, China.

Fusarium asiaticum is the predominant causal agent of Fusarium head blight (FHB) in southern China. The genetic diversity was assessed by analyzing 448 single-spore F. asiaticum isolates from 18 sampling sites that were 10 to 2,000 km apart, using seven highly informative variable number of tandem repeat (VNTR) markers. This analysis showed a significant degree of population subdivision (P < 0.001) among populations from upper, middle, and lower valleys of the Yangtze River, with little gene flow (Nm = 1.210). We observed a strong association between this genetic population subdivision and the mycotoxin produced. Our results show that the dramatic cline in trichothecene chemotypes may be explained by a recent and significant invasion of 3-acetyldeoxynivalenol (3ADON) producers in FHB pathogen composition in the middle valley. Using Bayesian statistics, we found a biased gene flow from 3ADON to nivalenol (NIV) populations. In addition, we observed significant genetic differentiation and linkage disequilibrium between NIV- and 3ADON-producing isolates at the same sampling sites. The impact of the changed agronomy and trade of cereal commodities on the spread of the new Fusarium population and the consequent increase of FHB observed in southern China are discussed.

Additional keywords:genetic variation.