Host Defenses Associated with Fruit Infection by Colletotrichum Species with an Emphasis on Anthracnose of Blueberries

Abstract

Defense mechanisms in fruit against invasion by fungal pathogens fall into several categories, including fruit physiological factors, passive defense responses, and active defense responses. Colletotrichum spp. are common fruit rot pathogens on a variety of crops. The infection strategy of Colletotrichum pp. varies depending upon the host and the tissue type being colonized and range from hemibiotrophy to necrotrophy. Anthracnose fruit rot caused by C. acutatum is the most important postharvest disease of blueberries (Vaccinium corymbosum). In order to better understand host resistance mechanisms in blueberry fruits, the resistant cultivar Elliott was compared with the susceptible cultivar Jersey. Higher levels of hydrogen peroxide and differentially expressed defense-related genes were found in ‘Elliott’ than in ‘Jersey’ fruit after inoculation. Furthermore, higher levels of anthocyanins and flavonols, including two distinctive compounds, were observed in Elliott fruits and two unique flavonols were present in Elliott. Additionally, pH and sugar content were implicated as being involved in host resistance in blueberry fruits. The results from these studies provide a significant contribution to the understanding of the multiple factors that contribute to anthracnose fruit rot resistance in blueberry. Accepted for publication 15 August 2013. Published 25 November 2013.