Colletotrichum fructicola is the dominant and one of the most aggressive species causing bitter rot of apple in Uruguay

Abstract

Forty-one isolates obtained from apple fruit exhibiting the typical symptoms of bitter rot in Uruguay were characterized based on molecular, phenotypic and pathogenicity data. Four species were identified based on the analysis of ITS, GAPDH and BTUB2 genes. The dominant species was Colletotrichum fructicola (33/41 isolates) followed by C. theobromicola (6/41 isolates), both belonging to the C. gloeosporioides species complex. The other species, with one isolate each, were C. melonis and Colletotrichum sp. both belonging to the C. acutatum species complex. Surprisingly, C. gloeosporioides and C. acutatum, commonly reported as the cause of bitter rot, were not found. Phenotypical traits were useful to assign the isolates to a species complex, but not to identify phylogenetic species. Isolates of all four species were able to cause the typical bitter rot disease, but the two species of the C. gloeosporioides species complex were the most aggressive based on lesion size.