Assessment of Pathogenicity and Aggressiveness of Fusarium poae on Wheat and Barley

ABSTRACT Fusarium head blight (FHB), primarily caused by Fusarium graminearum , poses a major threat to wheat and barley production. Although Fusarium poae is increasingly reported in cereal‐growing regions worldwide, its pathogenic potential in US wheat and barley remains underexplored. We compared the pathogenicity and aggressiveness of four F. poae isolates (GA18W 2.1.6, GA18W 5.2.4, GA18W 6.1.4 and GA19W 13.2.1II) and one reference F. graminearum isolate (GA18W 3.1.4) across seven cultivars (i.e., three soft red winter wheat, two durum wheat and two barley) classified as moderately resistant or susceptible. Greenhouse evaluations were conducted in 2021, 2022 and 2024 using single floret inoculation (SFI) and direct spray (DS). Disease severity (SEV), Fusarium ‐damaged kernels (FDK) and thousand‐kernel weight (TKW) were assessed. Main effects of the isolate, cultivar and inoculation method were significant for SEV, FDK and TKW ( p < 0.0001). As no consistent isolate‐level differences were detected among the four F. poae isolates, data were pooled for species‐level analysis. Across cultivars, inoculation methods and years, F. graminearum GA18W 3.1.4 produced higher SEV (47%–63%) and FDK (54%–76%) and reduced TKW (to 18 g) relative to pooled F. poae (SEV 14%–36%; FDK 32%–56%; TKW up to 24 g), with the greatest impacts in durum wheat. These results demonstrate that F. poae can contribute to FHB in US small‐grain cereals and support consideration of this species in resistance screening programmes.