Prevalence of the species involved in Fusarium head blight (FHB) in winter wheat in Wallonia, Belgium from 2010 to 2012

Abstract

Fusarium head blight (FHB) is a common plant disease occurring frequently in winter wheat in Belgium and associated with yield losses and mycotoxin contamination. The pathosystem involves a complex of species in the Fusarium and Microdochium genera. In order to evaluate the occurrence and distribution of the causal species in Wallonia, ears of winter wheat were collected in five experimental fields in 2010, 2011 and 2012. Grains from three positions along the rachis (top, middle and bottom) of each ear were investigated for the presence of FHB pathogens, using a plate isolation technique and monoconidial cultures. The species were identified using morphological and molecular (elongation factor 1-) characterization. Both infection prevalence and species occurrence differed from one location to another and from year to year, with one or more species being predominant each year. Some species were present one year, but absent in the following year. For example, in 2011, F. culmorum was the most predominant species, being present in every location, but it was rarely isolated in 2012 and it was absent in 2010. In each year F. graminearum, F. poae and F. avenaceum were isolated; F. poae was the prevalent species in 2010, and F. graminearum and F. avenaceum were the prevalent species in 2012. A rare and highly toxigenic species, F. langsethiae, was isolated in 2010 and 2012. In each year the proportions of FHB infection differed significantly (p < 0.01) between the three positions along the rachis, with an increasing intensity from top to bottom. The infections caused by F. graminearum, however, did not quite follow this gradient, with a slightly greater amount of infection found at the top than at the bottom. This discrepancy could result from the ability of this species to produce airborne ascospore inoculum. Our results highlight the great variation in the composition of the FHB complex, suggesting that the epidemiological characteristics differ from one species to another. Although the plate isolation technique is time consuming, it allowed a pathogen culture collection to be created that could be used for further characterization of the species and could improve the understanding of the epidemiology as well as disease/mycotoxin prediction