Effect of Chitosan on Growth and Toxin Production by Alternaria alternata f. sp. lycopersici

Abstract

<jats:p>The antifungal activity of chitosan, a bioplymer of β-1-4 gluscosamine, against <jats:italic>Alternaria alternata</jats:italic>, causal agent of black mold of tomato, was investigated. Chitosan was incorporated into potato dextrose broth (PDB) at concentrations of 100, 200, 400, 800, 1600, 3200, and 6400 μg·ml<jats:sup>–1</jats:sup>, growth and toxin production by the fungus were assessed after a 15-day incubation period. Chitosan significantly affected both growth and toxin production at higher concentrations. However, at lower concentrations, toxin production was affected more than the growth, as evidenced by minimum inhibitory concentrations (MIC) of chitosan derived for toxin production and mycelial growth. Excess sporulation of the fungus was observed in the presence of chitosan, but the spore viability was affected. Chitosan induced aggregation of fungal cells, abnormal shape, excess branching, and hyphal contortion. It also induced leakage of proteins from the fungal cells. The virulence of the toxin in culture filtrate of the fungus from different concentrations of chitosan was assayed by administering on tomato discs. Phospholipid content, electrolyte leakage, xylanase, and pectin methylesterase activity were measured in the culture filtrate administered tomato tissue. Decreased trend in causing electrolyte leakage, phospholipid degradation, and activation of xylanase and pectin methylesterase were observed with increasing concentrations of chitosan. The results showed that chitosan inhibits fungal growth at higher concentrations than toxin production. Further toxin produced at lower concentrations of chitosan was less virulent. Thus chitosan has potential as an antifungal agent.</jats:p>

Structural Characterization of Oligochitosan Elicitor from Fusarium sambucinum and Its Elicitation of Defensive Responses in Zanthoxylum bungeanum

“…By degradation of chitosan with a high molecular weight, oligochitosan with a low molecular weight and DP and excellent water solubility was obtained [30]. Oligochitosan has been shown to be more effective than chitosan in inhibiting the growth of various plant pathogenic fungi and eliciting various defense responses in plants, which can slow the development of plant diseases and directly or indirectly decrease disease severity [31,32,33,34]. TOCH was further purified to determine the effective fraction in TOCH that inhibited the infection of the pathogen.…”

Identification of yeast genes that confer resistance to chitosan oligosaccharide (COS) using chemogenomics

“…Chitosan inhibits both hyphal growth and spore germination [14] and reduces toxin production by plant pathogenic fungi [15]. Recently, chitosan has been shown to increase conidiation in filamentous fungi at concentrations where hyphal growth was impaired [8].…”

Evaluación in vitro de productos químicos no convencionales para el control de Penicillium citrinum

“…Finalmente, Hernández et al (2007) y Reddy et al (1998) mencionan que la excesiva esporulación del hongo sugiere una concentración sub-letal del tratamiento lo que da lugar a un proceso de estrés provocando la activación de mecanismos de defensa del patógeno asegurando la supervivencia hasta encontrar las condiciones favorables para su desarrollo. La eficacia de la combinación de los tratamientos puede ser atribuida en la capacidad de los compuestos de afectar el desarrollo del micelio y en consecuencia la formación estructuras de dispersión.…”