Partial cross-resistance of oats to different Fusarium species and the role of trichomes in susceptibility

Resistance of oats to FHB, caused by different Fusarium species, is important for grain quality and yield. In this study, 25 oat genotypes were evaluated for resistance to Fusarium graminearum (FG), F. sporotrichioides (FS) and F. poae (FP) in field trials across Germany to assess the presence of cross-resistance and to analyse the role of trichomes on the hulls during Fusarium infection. Infection severity was quantified by Fusarium species-specific qPCR and showed the highest fungal biomass for FP, followed by FS and FG. Variability due to environmental effects was very high, resulting in rather low heritabilities for FG (0.50) and FS (0.36), and no significant genotype effect for FP. A significant positive correlation was found between FP and FS infection, whereas FG infection was not correlated with either FP or FS. Microscopic analyses revealed important genotype-specific differences in trichome size and density on lemma and palea with very high heritability (0.97). FG biomass was positively correlated with trichome size and density, and FG hyphae were observed in close interaction with trichomes and stomata. These results indicate the presence of partial cross-resistance in addition to mostly species-specific resistance and suggest a role for trichomes in susceptibility to FG.