| Congresso Brasileiro de Microbiologia 2023 | Resumo: 1265-1 | ||||
Resumo:Fusarium oxysporum is a soilborne fungi and some strains are pathogenic to different plant species inducing either root-rots or tracheomycosis. While Alternaria alternata is a pathogenic fungus, saprophytic, capable to produce several mycotoxins in infected plants and/or in agricultural commodities, such as black rot of tomato, olive, carrots; and black and grey rot of citrus fruits. Management of these diseases through chemical methods causes environmental damage and induction of resistance in pathogens. Moreover, the consumers have demanded for no-contamination of perishable agricultural product with pesticide residues that impose potential harmful effects on their health. In this context, the use of chitosan as a natural antimicrobial and plant resistance inducer is an ecofriendly alternative against phytopathogenic fungi. Chitosan is a cationic amino polysaccharide composed of β-1, 4-D- glucosamine linked to N-acetyl-D-glucosamine residues, naturally present in fungal cell wall and commercially extracted from the thermochemical deacetylation of crustacean chitin. The aim of this study was to compare the growth-inhibitory effect, in vitro, of the fungal chitosan (FuCh) and crustacean chitosan (CrCh) against F. oxysporum and A. alternata. FuCh was extracted from Cunninghamella elegans biomass by alkali-acid treatment; and CrCh was obtained from Sigma-Aldrich Co. (St. Louis, USA), both chitosan presents around 75% deacetylation degree. Effects of FuCh and CrCh on radial mycelial growth were evaluated using the poisoned substrate technique (dilution in PDA medium) to obtain final chitosan concentrations of 5000 and 10000 μg/mL. Radial mycelial growth (mm) was measured using calipers every 24 h during 8 days or until the fungal growth reached the Petri dish border. Chitosan was replaced with sterile distilled water and 0.5% acetic acid in the positive control. Microbial growth was observed in all positive control. Results were expressed as percentage of mycelial growth inhibition (MGI%) compared to mycelial growth observed in control assays. CrCh at 10000 μg/mL showed a better MGI% against F. oxysporum (49.57%) and A. alternata (28.42%) but not statistically different from F. oxysporum (43.09%) when exposed to FuCh at 5000 μg/mL. MGI% values were directly proportional to the CrCh concetration, while the lower FuCh concentration resulted in greater MGI% values for both strains. The results obtained in this study demonstrate the antimicrobial activity of different chitosan (FuCh and CrCh) to control the mycelial growth of A. alternata and F. oxysporum. This biotechnological alternative is important for the establishment of a sustainable agriculture and to avoid the use of psticides.
Palavras-chave: antifungal effects, phytopathogenic fungi, polymer Agência de fomento:CNPq, Conselho Nacional de Desenvolvimento Científico e Tecnológico – Brazil e Fundação de Amparo a Ciência e Tecnologia do Estado de Pernambuco | |||||