Population structure and genetic diversity of Fusarium graminearum sensu stricto, the main wheat pathogen producing Fusarium head blight in Argentina

Abstract

Fusarium head blight (FHB) is a devastating disease of small grains cereal in Argentina. FHB is mainly associated with species within the Fusarium graminearum species complex, potential trichothecene producers. The control strategy success will be determined by the interaction among genetic variability of the pathogen, the host susceptibility and the environmental factors. The aim of this study was to evaluate the genetic variability of F. graminearum ss populations defined as temporal and spatial populations. Symptomatic spikes were collected during an FHB outbreak (2012/13) and a non-outbreak (2014/15) wheat-harvest season from wheat fields in Argentina. Strains were morphological and molecular analysed, of which four strains were Fusarium meridionale and 71 were Fusarium graminearum ss. The fungal populations assessed by ISSR molecular markers showed a genetic diversity (GD = 0.999–1.00) and migration rate Nm = 5 and structure population determined K = 2. Subpopulation 1 (K1) was established by 29 strains isolated from Marcos Juárez (MJ) and Pergamino (PER) during the 2012/13 and 2014/15 harvest seasons and subpopulation 2 (K2) was established by 46 strains isolated from Corral de Bustos (CBU) and Carlos Pellegrini (CPE) during the 2012/13 and 2014/15 harvest seasons. High genotypic and genetic diversity together with great differentiation within subpopulations and high gene flow would indicate that the strains isolated in Argentina are part of the same, unique and widespread population, as was already shown in a previous study. Understanding fungal genetic structure and continue monitoring of F. graminearum ss populations through different harvest seasons will assist not only breeders but also the development of improved management control strategies.