Detection of Colletotrichum acutatum latent infections in strawberry petioles and leaves

Abstract

Colletotrichum acutatum is the most significant agent of anthracnose strawberry fruit rot. Besides being a necrotrophic pest, it can spend a part of its life cycle as an epiphyte, in a form of latent infection. The presence of the fungi on symptomless plant tissue is considered one of the main ways of distribution of this economically harmful pathogen in the world. Investigation of latent C. acutatum infection was carried out on artificially inoculated strawberries. The initiation of fungi sporulation on symptomless petioles and leaves was carried out by exposing them to the herbicide paraquat (0.25%) and low temperatures, which caused plant tissue decay in different ways. Surface sterilization with 0.5% NaOCl precedes the exposure of plant material to paraquat. The freezing procedure was carried out by exposure of plant material to the temperature of -20?C for 2h. After the freezing, one group was rinsed in Tween 20 (18 ?l/l), and another group underwent surface sterilization in 0.0525% NaOCl with an addition of Tween 20 (18 ?l/l). After 6 days of incubation, the appearance of acervuli and conidia was detected in 93.33 to 100% plant parts exposed to paraquat treatment and freezing procedure. In inoculated parts which were not exposed to herbicides or low temperatures, the presence of acervuli was detected in 3.33% tested petioles and 6.67% leaves.