Antifungal activity of chitosan against Alternaria alternata and Colletotrichum gloeosporioides

Abstract

Chitosan and its derivatives have been reported as a promising alternative for control of postharvest fungal pathogens. The objective of this study was to evaluate in vitro and in situ antifungal activity of chitosan against Alternaria alternata and Colletotrichum gloeosporioides isolated from decayed apple fruits. The fungi were tested in vitro using PDA medium with three concentrations of chitosan (1, 2 and 3 mg/ml). Fungal growth of the test pathogens was significantly affected by all chitosan doses (P lt 0.05) after 7 days of incubation at 25°C. Water solution of 3 mg/ml of chitosan inhibited completely the conidial germination of A. alternata and C. gloeosporioides after 18 h incubation at 25°C. The results obtained from biocontrol assay indicate that the inhibition of postharvest decay of A. alternata and C. gloeosporioides was significantly influenced by chitosan concentrations. Disease incidence in chitosan-treated fruit after 7 days incubation at 25°C was significantly lower than in the positive control for both fungi tested (P lt 0.05). A. alternata and C. gloeosporioides used in this study were progressively inhibited in vitro and in situ with increasing concentrations of chitosan from 1 to 3 mg/ml.

Istraživanja pokazuju da su hitosan i njegovi derivati dobra alternativa u kontroli skladišnih fitopatogenih gljiva. Cilj ovog rada bio je da ispita antifungalnu aktivnost hitosana prema Alternaria alternata i Colletotrichum gloeosporoides, izolovanih sa inficiranih plodova jabuke, u in vitro i in situ uslovima. Rast gljiva je testiran in vitro koristeći PDA podlogu sa različitim koncentracijama hitosana (1, 2 i 3 mg/ml). Porast oba patogena je bio značajno smanjen (P lt 0.05) u svim koncentracijama hitosana nakon 7 dana inkubacije na 25°C. Vodeni rastvor hitosana koncentracije 3 mg/ml je u potpunosti inhibirao klijanje konidija A. alternata i C. gloeosporoides nakon inkubacije od 18 sati na temperaturi od 25°C. Rezultati ogleda in situ ukazuju da inhibicija propadanja plodova inficiranih sa A. alternata i C. gloeosporoides zavisi od koncentracije rastvora hitosana. Pojava bolesti na plodovima jabuka tretiranih rastvorom hitosana nakon 7 dana inkubacije na 25°C bila je značajno smanjena za obe vrste gljiva (P lt 0.05) u odnosu na pozitivnu kontrolu. Rast A. alternata i C. gloeosporoides je bio progresivno inhibiran in vitro i in situ sa povećanjem koncentracije rastvora hitosana, od 1 do 3 mg/ml.