Abstract
The antimicrobial effect of chitosan on Penicillium expansum, a major postharvest pathogen of pome fruit, and the possible mechanisms involved in its effect were examined in this study. Chitosan strongly inhibited spore germination and hyphal growth of P. expansum. Light microscopy and transmission electron microscopy observations revealed that chitosan also caused morphological changes in hyphae and conidia, such as abnormal branching and vacuolation. Proteomic changes in P. expansum after chitosan treatment were analyzed by two-dimensional electrophoresis (2-DE) and mass spectrometry (MS) analysis, and 26 proteins were ambiguously identified and categorized based on their putative biological function. Proteins related to DNA or protein biosynthesis, carbohydrate metabolism and energy production were decreased in relative protein abundance, while proteins involved in antibiotics resistance and defense response increased in relative protein abundance. Changes in abundance of these identified proteins were in accordance to the observed physiological and morphological changes of the fungi cells. Altogether, these experimental results provide a detailed illustration of the responses to chitosan in P. expansum, and widen our knowledge on the potential antifungal mechanisms of chitosan.
Highlights
The fungal pathogen Penicillium expansum is the causal agent of a major postharvest disease in pome fruits known as blue mold decay
Effect of chitosan on mycelial growth was estimated by measuring the colony diameter of P. expansum on potato dextrose agar (PDA) supplemented with different chitosan concentrations
After 7 days of incubation, fungal colony grew up to 41.2 mm in diameter on the control PDA, but the colony diameter was only 37.5, 31.4 and 23.9 mm on PDA supplemented with 0.01%, 0.05% and 0.1% chitosan, presenting inhibition rate of 9.0%, 23.8% and 42.0% respectively (Figure 1B)
Summary
The fungal pathogen Penicillium expansum is the causal agent of a major postharvest disease in pome fruits known as blue mold decay. Diverse studies have shown the efficiency of chitosan in controlling postharvest rot of horticultural commodities caused by plant pathogenic fungi, such as Aspergillus flavus (Dias et al, 2018), Botrytis cinerea (Lopes et al, 2014), Ceratocystis fimbriata (Xing et al, 2018), Pilidiella granati (Munhuweyi et al, 2017) and P. expansum (Wang et al, 2014). In addition to its potential to elicit plant defense by increasing the production of defense-related secondary metabolites and promoting the expression of defense-related enzymes (Hadwiger, 2013), chitosan exhibits direct antimicrobial activities against plant pathogens (Xing et al, 2015). The responses to chitosan in plant pathogenic fungi are far from well known, especially the responses occurred at omics level
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