Evaluation of the efficacy of different concentrations of chitosan for biocontrol of pathogenic fungi on Citrus

BACKGROUND AND OBJECTIVES The annual report shows that a significant amount of fruit and vegetables are lost due to postharvest decay. Orange is one of the most popular citrus fruits. Molds are the main cause of its spoilage and reduce the quality of the products. Currently, synthetic fungicides are the first choice of treatment worldwide. Chitosan is known as a biological control agent due to its non-toxicity, biodegradability, and biocompatibility, and it’s approved by the European Union RegEu۲۰۱۴۱۵۶۳ for plant protection. This study was carried out to isolate and identify the main pathogenic fungi in oranges and to evaluate the inhibitory effect of different concentrations of chitosan as a biocontrol agent.MATERIALS AND METHODSContaminated oranges were collected from the markets in Mohammadshahr City, Karaj, Iran. We isolated and selected five pathogenic fungi that were characterized macroscopically and microscopically by the slide culture method. The pathogenicity test was done in several stages to confirm the pathogenicity of the isolations. The isolated fungi were characterized based on genomic amplification and sequencing of the internal transcribed spacer region (ITS). In the next step, an aqueous chitosan solution with concentrations (۲, ۲.۵, ۳, and ۳.۵% w/v) is prepared by dissolving the specified amount in ۱% acetic acid. After adjusting the pH to ۵.۶, the antimicrobial property of these solutions was tested against a suspension of ۱۰۶ conidia/ml of each pathogenic fungus using the well diffusion test.RESULTS AND DISCUSSIONThe contaminated oranges were used for the isolation of pathogenic fungi, and these strains were tested for their ability to cause decay in healthy oranges. Five strains with the strong pathogenicity were characterized morphologically. Molecular identification indicates that the fungal strains belong to Penicillium italicum, Penicillium rastrickii, Aspergillus ustus, Alternaria terricola, and Alternaria alternata, respectively. The well diffusion test shows, the best concentration of chitosan was ۳ percent (w/v), and we had the largest diameter of the zone of non-growth in this concentration.CONCLUSION This study suggests that a proper concentration of chitosan can be considered a potential biocontrol agent for the management of postharvest citrus diseases caused by some pathogenic fungi.

کلیدواژه ها:

Orange Fruit ، Citrus ، Postharvest ، Pathogen ، Chitosan