Exploring the microbial communities associated with Botrytis cinerea during berry development in table grape with emphasis on potential biocontrol yeasts

Abstract

Table grapes harbour a wide diversity of microbes, some of which are potential biocontrol agents that may be responsible for the control of fungal pathogens in the phyllosphere. This study evaluated the diversity of microbial communities associated with naturally present Botrytis cinerea inoculum, with special emphasis on populations of potential biocontrol yeasts during berry development in table grapes. Samples were collected from two agro-ecological habitats in South Africa (Northern Province), characterised by low rainfall (site A) and high rainfall (site B). The phenological development samples included those at full bloom, pea size and mature berry stages. Within the group of yeasts known to be natural antagonists, Aureobasidium, Cryptococcus, Rhodotorula and Sporobolomyces could be cultured, while pathogenic fungal genera from asymptomatic samples included Cladosporium, Alternaria, and Aspergillus. Botrytis cinerea could only be cultured at the harvest stage from symptomatic and asymptomatic berries. Overall, the study showed the highest prevalence of Alternaria (35.6%), Cladosporium (27.2%) and Rhodoturula (21.2%). In conclusion, the study reveals a diverse pathogenic and beneficial naturally-known yeast genera in the presence of B. cinerea. Such information and knowledge can be further explored to manipulate potential antagonistic populations to prevent establishment of pathogenic populations and secure dominance of antagonistic populations at the harvest stage.