Physico-Chemical Characteristics and Culturable Microbial Communities of Grape Berries Change Strongly during Noble Rot Development

Botrytis cinerea is a well-known pathogen of grapevine. However, under certain microclimatic conditions, Botrytis infection results in noble rot, an essential process in the production of the world-known Tokaji aszu wines in Hungary. We investigated the physico-chemical characteristics and culturable microorganisms associated with grape berries through several noble rot phases in the two main cultivars grown in Tokaj: Vitis vinifera cv. "Furmint" and "Harslevelu". We measured physical and analytical parameters routinely tested in viticulture and analyzed the ITS rDNA sequence data of fungi isolated from the sampled berries. We observed significant differences in the physico-chemical parameters among the noble rot phases as well as sampling dates. The greatest variation in berry texture and microbial structure was observed in the initial phases, with variables converging as the noble rot progressed. By finding a bijection between the examined chemical properties and the factorial parameters (e.g., noble rot phase, collection time, cultivar), an appropriate sweet winemaking material can be designed. Fungal community differed significantly among cultivars, with higher number of species observed in Harslevelu. Our results reveal that there is more to noble rot than only Botrytis cinerea and other microorganisms may play important roles in the aszu process.