An improved approach for the accurate determination of fungal pathogens in diseased plants

Abstract

A simple and accurate method for the determination of the mass of chitin-containing fungal pathogens in plants is reported. It is based upon the release of glucosamine from fungal chitin by hydrochloric acid hydrolysis. In order to obtain reliable results, four steps were needed: (1) isolation of the chitin-containing fraction from an infected plant, i.e. the cell wall fraction, (2) selection of a suitable hydrolysis, (3) purification of the hydrolysates and (4) glucosamine determination by a specific method. This procedure was then applied, during the course of infection, to different organs (stems, leaves and cotyledons) of melon seedlings inoculated with Colletotrichum lagenarium. The fungal growth curves in stems and leaves were then compared to the curves of proteolytic activity that developed in the infected stems and leaves at the same time. It is shown that this method enables us to correlate biochemical events appearing in plants after infection with the fungal mass they contain.