Abstract
BackgroundChitosan has shown potential for the control of Fusarium head blight (FHB) disease caused by Fusarium graminearum. The objective of this study was to compare the effect of chitosan hydrochloride applied pre- or post-fungal inoculation on FHB and to better understand its’ mode of action via an untargeted metabolomics study.ResultsChitosan inhibited fungal growth in vitro and, when sprayed on the susceptible wheat cultivar Remus 24 hours pre-inoculation with F. graminearum, it significantly reduced the number of infected spikelets at 7, 14 and 21 days post-inoculation. Chitosan pre-treatment also increased the average grain weight per head, the number of grains per head and the 1000-grain weight compared to the controls sprayed with water. No significant impact of chitosan on grain yield was observed when the plants were sprayed 24 hours post-inoculation with F. graminearum, even if it did result in a reduced number of infected spikelets at every time point. An untargeted metabolomic study using UHPLC-QTOF-MS on wheat spikes revealed that spraying the spikes with both chitosan and F. graminearum activated known FHB resistance pathways (e.g. jasmonic acid). Additionally, more metabolites were up- or down-regulated when both chitosan and F. graminearum spores were sprayed on the spikes (117), as compared with chitosan (51) or F. graminearum on their own (32). This included a terpene, a terpenoid and a liminoid previously associated with FHB resistance.ConclusionsIn this study we showed that chitosan hydrochloride inhibited the spore germination and hyphal development of F. graminearum in vitro, triggered wheat resistance against infection by F. graminearum when used as a pre-inoculant, and highlighted metabolites and pathways commonly and differentially affected by chitosan, the pathogen and both agents. This study provides insights into how chitosan might provide protection or stimulate wheat resistance to infection by F. graminearum. It also unveiled new putatively identified metabolites that had not been listed in previous FHB or chitosan-related metabolomic studies.
Highlights
Chitosan has shown potential for the control of Fusarium head blight (FHB) disease caused by Fusarium graminearum
Chitosan inhibits the growth of F. graminearum in vitro Both solid and liquid culture antifungal activity tests were performed to evaluate the response of F. graminearum to a range of concentrations of chitosan incorporated into Potato Dextrose Agar (PDA) or Potato Dextrose Broth (PDB)
Chitosan reduces the severity of FHB when applied pre‐ or post‐fungal inoculation After verifying that chitosan could inhibit the growth of F. graminearum in vitro, the objective of the research was to validate that it could be used to control FHB disease caused by F. graminearum in wheat, either as a preventative or curative treatment
Summary
Chitosan has shown potential for the control of Fusarium head blight (FHB) disease caused by Fusarium graminearum. Wheat production is threatened by fungal diseases that are estimated to detrimentally affect grain yields by 15-20% per annum [1, 2]. Fusarium head blight (FHB), called Fusarium ear blight or scab, is one of the major fungal diseases affecting global wheat production. F. graminearum and F. culmorum both cause significant yield losses and contaminate grain with harmful mycotoxins, including trichothecenes and zearalenone [3]. Fusarium species can infect the seeds and seedlings of new plants growing in the field, causing Fusarium seedling blight (FSB) [4, 5] and Fusarium root rot (FRR) diseases [6]
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