Genome-wide association studies of Fusarium head blight resistance in winter bread wheat lines

Fusarium Head Blight (FHB) is an important cereal disease worldwide and has become an essential breeding target in wheat. FHB generates considerable losses in terms of grain yield and quality of the seeds in cereal crops. The mycotoxins produced by some Fusarium species, such as deoxynivalenol (DON), directly impact the farmers. In fact, DON accumulation results in unmarketable harvest due to the associated health hazards (vomiting, diarrhea, fever etc). Facing DON risks, the European Commission had to establish a maximum concentration of the mycotoxin in unprocessed cereals. Avoidance mechanisms of the plants against disease infections were identified in diverse studies and are known as the passive resistance. These mechanisms related to phenotypic traits such as variations in plant height (PH), heading date (HD) or the presence of awns could possibly reduce the FHB infection of the wheat. On another hand, the active resistance is determined by genetic factors so called quantitative trait loci (QTL). QTL identification via population mapping was established to be a useful tool to find loci regions associated with FHB resistance. Therefore, in this study we aimed to find phenotypic and genotypic correlations with Fusarium Head Blight resistance among 108 winter bread wheat genotypes. By estimating the heritability of the agronomic traits, we wanted to determine if it would be efficient to breed for those traits. Furthermore, we had the objective to detect FHB resistance QTL from our winter bread wheat genotypes and finally, to observe the overlapping QTL’s regions between FHB resistance and the QTL of the HD or of the PH. It was found that the HD had strong negative phenotypic and genotypic coefficients of correlation with FHB severity and DON concentration. The HD had also an important heritability and direct effect on FHB severity. By performing a GWAS analysis, QTL associated to FHB resistance were found on the chromosomes 1B, 2B, 3A, 3B, 5A, 5B, 5D, 6A, 6B ,7B among the studied genotypes. Overlapping QTL were observed between FHB resistance and HD on the chromosomes 1B, 2B, 3B, 5A, 5B, 6B but also between FHB resistance and PH on the chromosomes 2B, 3A, 3B, 5A, 6A. In conclusion, the HD was considered as an escape mechanism against FHB. It seems to be feasible to select chromosomes fragments with favorable QTL for FHB genetic resistance. Those traits could be involved in marker assisted or genomic selection programmes after the approval of the observed QTL detected to develop FHB resistant cultivars

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