Analysis of yeast flora associated with grape sour rot and of the chemical disease markers.

The frequency and the density of the species associated with grape sour rot in different cultivars were determined. The most frequent species in the rotten grapes, Candida krusei, Kloeckera apiculata, and Metschnikowia pulcherrima, and a less frequent species, Issatchenkia occidentalis, when inoculated with Saccharomycopsis crataegensis were able to induce in vitro the symptoms of the disease. The gas chromatographic determination of the volatile compounds in the headspace was used to evaluate the metabolic role of the different species associated with the disease. These analyses made it possible to presume that, whereas some species, such as Candida krusei and Hanseniaspora uvarum, can be considered responsible for these modifications and in particular for the ethyl acetate production, others, such as Saccharomycopsis crataegensis, can promote the development of the former species.