Uso da quitosana no controle de fitopatógenos

Abstract

Fungicides, often used in conventional farming systems, can damage humans, animals and the environment. Chitosan, which is a substance extracted from the crustacean shell, has shown to be a harmless and cheap alternative. This study aimed to test the inhibitory effect of chitosan on the mycelial growth of Fusarium sp., Rhizoctonia sp. and Trichoderma sp. Different concentrations of chitosan (1.0%; 2.0%; 4.0%; 8.0% and 16.0%) were supplemented to 1% acetic acid Potato Dextrose Agar (PDA). The fungi were inoculated in the center of the plates, incubated at 25°C, with and without a 12-hour photoperiod. The measurements were performed daily, in two transverse diameters, until the mycelium of the fungi reached the edges of the Petri dish. The mycelial growth of Fusarium sp. was significantly inhibited by chitosan at concentrations 1.0%; 2.0%; 4.0% and 8.0%; on the 4th, 5th and 6th evaluation days, in a 12-hour photoperiod. However, for Rhizoctonia sp. there was no reduction of mycelial growth. Trichoderma sp. presented the greatest mycelial reduction, in both light conditions, in all the concentrations evaluated, on days one, two and three. It can be concluded that the mycelial growth of Fusarium sp. and Trichoderma sp. were inhibited by chitosan. Also, that the association of chitosan with Trichoderma sp. is not indicated as biocontrol agents of phytopathogens.