Epsilon Archive for Student Projects

Abstract

Fusarium head blight (FHB) is a major fungal disease and a serious threat to food and feed safety around the globe. It primarily affects small-grain cereals, reducing yield and contaminating grain with mycotoxins. The polygenic and quantitative nature of FHB resistance in cultivated barley (Hordeum vulgare) is a major bottleneck for durable resistance. This study evaluated FHB resistance in a diverse panel of wild barley (Hordeum vulgare subsp. spontaneum) genotypes from the Wild Barley Diversity Collection (WBDC) using a detached leaf assay under three treatments: uninoculated control, single-species infection with Fusarium graminearum, and mixed-species co-infection with three species: F. graminearum, F. avenaceum, and F. culmorum. Disease severity was assessed using two complementary phenotyping approaches: conventional visual disease scoring and image-based lesion quantification using ImageJ. Both methods revealed a highly significant effect of treatment on disease severity, substantial genotypic variation in susceptibility, and a significant genotype-by-treatment interaction, indicating that the relative ranking of genotypes shifted depending on infection type. Several genotypes showed consistent low and high disease indices across both scoring methods. WBDC-110 and WBDC-164 were among the most susceptible genotypes with both methods, whereas WBDC-060, WBDC-034 and WBDC-120 were the three least susceptible, suggesting partial resistance worth further characterisation. Co-infection did not affect all genotypes in the same way: it increased disease in some genotypes but reduced it in WBDC-110 and WBDC-164, the genotypes most damaged by F. graminearum alone. Molecular assays were also used to complement the phenotypic data. In two contrasting genotypes, WBDC-060 and WBDC-159, the F. graminearum-specific FG16N PCR assay detected the pathogen in single-species infected leaves but not in co-infected leaves. In contrast, a deoxynivalenol (DON)-type Tri13 sequence was detected only in co-infected samples, and no nivalenol (NIV)-type sequence was detected in any sample. These results suggest that co-infection changes the composition of the fungal community in the leaf, possibly through competition with F. graminearum, and that the DON-type signal in co-infected leaves may come from F. culmorum; quantitative methods are needed to test these explanations. These findings highlight the value of combining phenotypic and molecular approaches when characterising FHB resistance, and point to wild barley genotypes such as WBDC-060 as promising candidates for further resistance breeding and mechanistic study.