Multilocus-Derived Genetic Variability and Pathogenicity of <i>Colletotrichum</i> Species from the Mid-Atlantic United States Associated with Anthracnose in Pepper

Colletotrichum species are important fungal pathogens that cause fruit rots leading to pre and postharvest losses of a broad range of Solanaceae crops, including bell and non-bell pepper and fresh-market and processing tomato. We performed a phylogenetic and pathogenic characterization of Colletotrichum isolates collected in the Mid-Atlantic United States from mature and immature Capsicum annum and Solanum lycopersicum fruits. A total of 149 Colletotrichum sp. isolates were obtained, distributed among 18 different gapdh locus-based haplotypes, and 11 recognized Colletotrichum species according to a multilocus-based analysis. Pathogenicity tests demonstrated that of 61 tested isolates, 59 were pathogenic on mature bell pepper (red) fruits under controlled conditions. C. scovillei isolates caused disease on immature bell pepper (green) fruits during artificial inoculations. Additionally, other selected Colletotrichum isolates displayed variable aggressiveness on mature pepper fruit. Represented among the pathogenic isolates, there were three species of Colletotrichum not yet reported as pathogens of Capsicum anywhere in the world, C. melonis, C. changpingense and C. chlorophyti. Four additional Colletotrichum species, C. fioriniae, C. aenigma, C. fructicola, and C. sojae are also reported for the first time causing disease on Capsicum sp. in the United States. These results demonstrate the extreme heterogeneity of Colletotrichum species causing fruit rot in immature and mature bell peppers and mature tomato in the Mid-Atlantic United States, and their pathogenic differences on pepper under controlled conditions. Accurate identification of the pathogenic species of Colletotrichum causing fruit rot is a critical step for making informed disease management decisions in pepper and tomato production.