Molecular characterization of the Fusarium graminearum species complex in Eastern China

Members of the Fusarium graminearum species complex (FGSC) cause Fusarium head blight in small cereal grains all over the world. To determine the species and trichothecene chemotype composition and population structure of FGSC in Jiangsu and Anhui provinces, an area where epidemics occur regularly, 891 isolates were collected in two consecutive years (2011 and 2012) and characterized with species- and chemotype-specific polymerase chain reaction. Of the 891 isolates typed, 83 were F. graminearum sensu stricto (s. str.) and 808 were F. asiaticum. All 83 F. graminearum s. str. isolates were of a 3ADON (26.51 %) or 15ADON (73.49 %) type, while F. asiaticum isolates included 696 3ADON producers, 46 15ADON producers, and 66 NIV producers. Eight variable number tandem repeat (VNTR) markers were tested on a representative 384 F. asiaticum isolates from 55 sampling sites. VNTR analysis showed high gene diversity and genotypic diversity but low linkage disequilibrium in both populations Fg2011 and Fg2012 grouped based on the year of collection. Low genetic differentiation (F (ST) = 0.026) and high gene flow (N (m) = 15.13) was observed between the two populations and among subpopulations within the same population (N (m) = 3.53 to 48.37), indicating that few influence of temporal and spatial variations on population differentiation in this area. Similar result was obtained from 3ADON, 15ADON and NIV populations or carbendazim resistant and sensitive populations, indicating that chemotype of Fusarium isolates and carbendazim application had minor influence on population subdivision.