Roles of Three FgPel Genes in the Development and Pathogenicity Regulation of Fusarium graminearum

Fusarium head blight (FHB) is a devastating fungal disease caused by Fusarium graminearum. Pectin lyase, a pectinase, acts on the α-1,4-glycosidic linkage of galacturonic acid primarily by β-elimination. In this study, three pectin lyase genes (FgPel1, 2, 3) in F. graminearum were selected, and deletion mutants (ΔFgPel1, 2, 3) were constructed by homologous recombination for functional characterization. The gene deletions affected the morphology and growth rate of F. graminearum on pectin medium at various concentrations, with the growth rate of ΔFgPel1 being more significant. The growth of ΔFgPel1 colonies slowed at pH 4, with optimal growth at pH 6.5, whereas ΔFgPel2 and ΔFgPel3 exhibited greater inhibition at pH 8. Colony morphology and diameter of the deletion mutants showed no significant differences compared to the wild-type strain PH-1, and there was no effect on conidial production or germination rate. Pathogenicity assays demonstrated that gene deletion significantly reduced the ability of F. graminearum to infest corn silks and wheat ears, and that ΔFgPel2 showed a more pronounced reduction in pathogenicity on wheat spikes. In summary, the pectin lyase genes (FgPel1, 2, 3) are involved in pectin utilization and are influenced by external pH conditions, which attenuate the pathogenicity of F. graminearum without affecting its vegetative growth or asexual spore formation. These findings elucidate the roles of these genes and provide a basis for controlling FHB.