Abstract
BackgroundFusarium graminearum sensu stricto (s.s.) is an ubiquitous pathogen of cereals. The economic impact of Fusarium head blight (FHB) is characterized by crop losses and mycotoxin contamination. Our objective was to associate SNP diversity within candidate genes with phenotypic traits. A total of 77 F. graminearum s.s. isolates was tested for severity of fungal infection (= aggressiveness) and deoxynivalenol (DON) production in an inoculated field experiment at two locations in each of two years. For seven genes known to control fungal growth (MetAP1, Erf2) or DON production (TRI1, TRI5, TRI6 TRI10 and TRI14) single nucleotides polymorphic sites (SNPs) were determined and evaluated for the extent of linkage disequilibrium (LD). Associations of SNPs with both phenotypic traits were tested using linear mixed models.ResultsDecay of LD was in most instances fast. Two neighboring SNPs in MetAP1 and one SNP in Erf2 were significantly (P < 0.05) associated with aggressiveness explaining proportions of genotypic variance (pG) of 25.6%, 0.5%, and 13.1%, respectively. One SNP in TRI1 was significantly associated with DON production (pG = 4.4).ConclusionsWe argue that using the published sequence information of Fusarium graminearum as a template to amplify comparative sequence parts of candidate genes is an effective method to detect quantitative trait loci. Our findings underline the potential of candidate gene association mapping approaches to identify functional SNPs underlying aggressiveness and DON production for F. graminearum s.s populations.
Highlights
Fusarium graminearum sensu stricto (s.s.) is an ubiquitous pathogen of cereals
The specific objectives of our study were to: (i) investigate the nucleotide diversity on gene level, (ii) investigate the extent of linkage disequilibrium (LD) between single nucleotide polymorphic sites (SNPs) within and among candidate genes, (iii) identify single nucleotides polymorphic sites (SNPs) of candidate genes Erf2 and MetAP1 for testing whether they affect the quantitative variation for aggressiveness, and (iv) evaluate associations of SNPs in TRI1 and other four genes of the TRI5 cluster with variation in DON production
Association mapping based on candidate genes is a promising tool for high-resolution mapping of genes contributing to quantitative traits [23]
Summary
Fusarium graminearum sensu stricto (s.s.) is an ubiquitous pathogen of cereals. The economic impact of Fusarium head blight (FHB) is characterized by crop losses and mycotoxin contamination. Our objective was to associate SNP diversity within candidate genes with phenotypic traits. For seven genes known to control fungal growth (MetAP1, Erf2) or DON production (TRI1, TRI5, TRI6 TRI10 and TRI14) single nucleotides polymorphic sites (SNPs) were determined and evaluated for the extent of linkage disequilibrium (LD). Only one QTL (quantitative trait locus) study from a single cross was reported detecting at least two QTL for aggressiveness [12]. It was shown before, that a large amount of molecular variation was found within field populations of F. graminearum s.s. using SSR (simple sequence repeat) markers. Because LD is species and population specific, it should be determined before conducting an association mapping study
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