The effect of foliar chitosan application on fusarium head blight in barley is highly genotype dependent

BACKGROUND: Fusarium head blight (FHB) is a severe disease of barley that reduces yield and grain quality through contamination with mycotoxins. Conventional disease management provides only partial control under field conditions. Elicitors such as chitosan, a natural biopolymer, are promising alternatives to enhance plant resistance, but the efficacy of induced resistance may depend on host genotype and environmental conditions. RESULTS: We investigated the effect of chitosan on FHB resistance in 39 diverse spring barley genotypes inoculated with Fusarium culmorum. Greenhouse experiments revealed reduced FHB severity and fungal DNA contents in several genotypes following chitosan pre-treatment and strong genotype-dependent effects. Field experiments at two locations indicated that chitosan treatment can reduce FHB severity under natural infection conditions, though the effects varied depending on genotype and environment. The cultivar Marthe consistently showed enhanced resistance across independent experiments. In addition, Chitosan pre-treatment induced ethylene production in barley leaves, suggesting activation of stress-related signalling pathways. However, ethylene release was attenuated after a second chitosan exposure, indicating a modulation of stress responses. Gene expression analysis of defence-related and Fusarium-responsive genes indicated a mitigated stress response in chitosan-induced barley. This may reflect reduced fungal success and suggests that chitosan induction of resistance might result in a physiologically cost-efficient defence mechanism in barley. CONCLUSIONS: Chitosan is a strong inducer of barley disease resistance with potential for integration into FHB management. Our results demonstrate that elicitor-induced resistance is a quantitative and genotype-dependent trait, and that cultivar-specific responses are likely transferable from controlled to field conditions. Identifying genotypes, such as Marthe, with consistent responsiveness to bioactive stimulants, offers breeding potential for optimised elicitor-induced resistance. This could support more sustainable FHB management strategies in barley in the future.