Morphological Diversity and Mycelial Compatibility of Botrytis pseudocinerea and Botrytis cinerea Isolated in Latvia

Botrytis is one the most economically important fungal taxa, comprising pathogens that infect a wide range of crops and causing gray mould. Two morphologically indistinguishable species, Botrytis cinerea and B. pseudocinerea, are significant pathogens found in close association in the same niches all over the world. Both species cause the same diseases in many plants; however, their mycelial compatibility in Latvia has not been reported. The aim of this study was to compare the morphological characteristics of B. cinerea and B. pseudocinerea isolates and determine their compatibility based on culturing on potato dextrose agar (PDA) media. A total of 113 isolates with the characteristic colony morphology of Botrytis spp. were obtained from four different host plants: tomato (Solanum lycopersicum), faba bean (Vicia faba), strawberry (Fragaria × ananassa), and cranberry (Vaccinium macrocarpon). The obtained isolates were divided into ten groups based on their morphological traits and hosts, and representatives from each group were chosen for further analyses. Botrytis spp. were identified at the species level using the DNA sequences of three protein-coding genes (RPB2, DNA-dependent RNA polymerase II; HSP60, heat shock protein 60; and G3PDH, glyceraldehyde 3-phosphate dehydrogenase). All ten isolates (five B. cinerea and five B. pseudocinerea) were pathogenic on wounded leaves and stems of ten-week-old tomato plants, and the pathogen was re-isolated and identified to fulfill Koch’s postulates. A high degree of phenotypic diversity was observed between and within B. cinerea and B. pseudocinerea. Mycelial compatibility was found to vary depending on the species, particular isolate, and host plant. This is the first report of B. pseudocinerea as a causal agent of gray mould on tomatoes in the Baltic region.