The North American cranberry fruit rot fungal community: a systematic overview using morphological and phylogenetic affinities

Cranberry fruit rot (CFR) is caused by many species of fungi, with the contribution of any given species to the disease complex varying among plantings of Vaccinium macrocarpon within a site, sites within regions, and among regions and years. This study assessed the morphological and molecular variability of five widespread CFR-causing fungi: Phyllosticta vaccinii, Coleophoma empetri, Colletotrichum acutatum, Colletotrichum gloeosporioides and Physalospora vaccinii. Although the majority of isolates had morphological characteristics consistent with published descriptions, some were atypical. For example, non-chromogenic isolates of C. acutatum were recovered from British Columbia and white isolates of Physalospora vaccinii were recovered in addition to the more common dark isolates. On the basis of sequence analysis of the ITS and large subunit rDNA (LSU), it appears that Phyllosticta vaccinii, C. empetri, C. gloeosporioides and C. acutatum are genetically uniform on cranberry in North America. This suggests the possibility that these fungal species were introduced to cultivated cranberries and concomitantly moved with planting material to new locations. In contrast, white isolates of Physalospora had ITS and LSU sequences distinct from those of their dark counterparts, with phylogenetic analyses suggesting that these isolates represent either different species or distinct members of highly divergent populations. Taxonomic placement of all species based on phylogenetic relationships was consistent with morphological placement, with the exception of Physalospora vaccinii. Unlike other Physalospora species, CFR isolates of Physalospora vaccinii were not allied with the Xylariomycetidae; instead, these fungi were members of the Sordariomycetidae. A deeper taxonomic analysis is needed to resolve this inconsistency in familial affiliation.