Botrytis michiganensis: A New Botrytis Species Causing Blossom Blight on Highbush Blueberries

Highbush blueberries (Vaccinium corymbosum) are an important fruit crop worldwide, and Michigan is one of the largest producers within the United States. Botrytis blossom blight and fruit rot are major diseases in this region. Although Botrytis cinerea has long been considered the primary causal agent, a recent study identified a novel species in Michigan. In this article, we describe a new species, B. michiganensis, as an additional pathogen causing blossom blight. This study aimed to characterize B. michiganensis through multilocus phylogenetic analysis (G3PDH, HSP60, RPB2, NEP1, and NEP2), morpho-cultural traits, and fungicide sensitivity. Phylogenetic analyses, using both individual and concatenated gene sequences, placed B. michiganensis in a distinct clade closely related to B. fabiopsis, B. caroliniana, and B. galanthina. The isolates exhibited diverse cultural and morphological characteristics on potato dextrose agar, ranging from white to gray fluffy/cottony mycelia. None of the isolates produced conidia on artificial media but developed typical Botrytis-like conidiophores and conidia on inoculated plant tissues, characterized by hyaline to pale brown, elliptical to ovoid conidia and branching conidiophores. Pathogenicity tests on blueberry tissues, green grapes, and white rose petals confirmed its ability to cause Botrytis blossom blight and fruit rot, with disease severity comparable to B. cinerea. Fungicide sensitivity assays revealed that B. michiganensis isolates were sensitive to all tested fungicides except cyprodinil. These findings provide new insights into the Botrytis species complex affecting blueberries and highlight the need for further diversity studies.