Genetic and phenotypic diversity within the Fusarium graminearum species complex in Norway

Abstract

As has been observed in several European countries, the frequency of Fusarium head blight (FHB) caused by members of the Fusarium graminearum species complex (FGSC) has increased in Norwegian cereals in recent years, resulting in elevated levels of deoxynivalenol in cereal grains. The objective of this study was to determine if this increase was associated with changes in FGSC composition within Norway. FGSC isolates collected from wheat, oats and barley in Norway during two periods, mainly 1993-1998 and 2004-2007, were characterized to determine species and trichothecene genotype composition and to assess levels of genetic variation and population structure. In vitro growth rates at different temperatures and aggressiveness in spring wheat were further characterized for a sub-selection of isolates. All Norwegian isolates were identified as F. graminearum. The 3-acetyl-deoxynivalenol (3-ADON) trichothecene type was dominant. However, isolates with the 15-ADON chemotype were detected in Norway for the first time and may represent a recent introduction of this trichothecene type. Bayesian-model based clustering and analyses of genetic differentiation indicated the persistence over the last 20 years of two sympatric and partially admixed populations of F. graminearum in Norway. Significant differences in average in vitro growth rates and aggressiveness were observed between these two populations. Our results demonstrate that the recent increase in prevalence of the FGSC in Norwegian cereals do not correspond to any dramatic changes in FGSC species or trichothecene chemotype composition. However, significant changes in population frequencies were observed among Norwegian F. graminearum.

Variances in trichothecene chemotype distribution in Lithuanian wheat grain and within pure culture Fusarium graminearum isolated from the same grain samples

“…Co-occurrence of 3ADON and 15ADON chemotypes in grain samples is high (Table 4), which indicates that 15ADON somehow may be easier to isolate than 3ADON fungi. A recent study on phenotypic traits of different F. graminearum chemotypes by Aamot et al (2015) shows that 15ADON chemotype strains are more aggressive than 3ADON, which may explain why 15ADON is more often isolated from infected plant-heads, but the same study suggests that 15ADON grows slower than 3ADON on PDA at 20°C and 25°C, which contradicts our pure culture isolation results, where grain were plated on PDA and grown at 25°C, but still 15ADON strains were dominant among those isolated. Some North American studies (Ward et al 2008;Guo et al 2008) indicate that aggressiveness levels of chemotypes are the other way around, with 3ADON strains considered to be the more aggressive ones.…”

Glutathione-Conjugates of Deoxynivalenol in Naturally Contaminated Grain Are Primarily Linked via the Epoxide Group

“…The chromatographic separation of the two isomers has rarely been shown but was recently achieved using a similar HPLC column chemistry (pentafluorophenyl) as was used in this study for separation of DON–thiol isomers [18]. While DON-3- O -acetate is a common contaminant of cereal grain in Norway [19], this is the first report of DON-15- O -acetate in Norwegian grain and corresponds well with the DON-15- O -acetate producing genotypes of Fusarium graminearum observed for the first time in Norway in 2006 [20]. The identity of the two DON-acetates was supported by comparison of the LC-HRMS/MS spectra of the [M + H] + ions in the reference standard and the oat extract (Figure S3).…”

Associations betweenFusarium species and mycotoxins in oats and spring wheat from farmers’ fields in Norway over a six-year period

“…15-ADON was not analysed in our study. However, isolates with the 15-ADON chemotype have recently been detected in Norway (Aamot et al, 2015). Thus, it needs to be considered whether 15-ADON analysis should be included in future surveys.…”