Genetic Diversity and Differential Host Pathogenicity Among Colletotrichum Causing Pepper and Tomato Anthracnose

Anthracnose fruit rot is one of the most serious diseases affecting the production of tomato (Solanum lycopersicum) and pepper (Capsicum annum) in the United States. The disease is typically incited by Colletotrichum coccodes, C. gloeosporioides or C. dematium. Anthracnose has been typified as a disease of ripe fruit. However, Colletotrichum isolates causing disease on immature pepper fruit are becoming increasingly prevalent in Ontario and Midwestern, Southeastern and Mid-Atlantic production areas. Diverse tomato and pepper fruit rotting fungal isolates from infected fruit grown in the Mid-Atlantic region and previously described Colletotrichum exemplar strains were cultured from the U.S. National Fungus Collections. Pathogenicity of respective isolates on mature and immature tomato and pepper fruit was determined. Genomic DNA was extracted and nucleotide sequences of the rDNA-ITS region were determined. Phylogenetic analysis using maximum likelihood identified 15 clades among the 160 isolates evaluated. Based upon ITS similarity, isolates were assigned to Colletotrichum aggregate groups. Both tomato and pepper isolates grouped within the C. acutatum, C. gloeosporioides, C. truncatum and C. dematium/C. destructivum aggregates. Multi-locus phylogenetic analysis using nucleotide sequence markers for GADPH, H3, ACT, CHS, and ITS data were utilized to determine species identities and determine lineage of isolates from different production regions and hosts. Opportunities to characterize fungal infection strategies and fruit defense responses will be discussed.