Temperature Requirements Can Affect the Microbial Composition Causing Sour Rot in Grapes

Sour rot (SR) is a late-season non-Botrytis rot affecting grapevines, resulting from a complex interplay of microorganisms, including non-Saccharomyces yeasts and acetic acid bacteria. Nonmicrobial factors contributing to disease development encompass vectors (e.g., Drosophila spp.), the presence of wounds or microcracks on grape berry surfaces, and environmental conditions during berry ripening. The microbial complexes within SR-affected grapes exhibit variability among different bioclimates and seasons, with certain microorganisms predominating under specific conditions. This study examined the influence of environmental conditions on the microbiome composition associated with SR-affected grape bunches, utilising data from 41 locations across three distinct Italian bioclimates. We selected nine yeast and two bacterial species frequently isolated from sour-rotted grapes for analysis. The growth responses of these microorganisms to temperature were assessed by categorising them into four ecophysiological clusters. Furthermore, we analysed the distribution of these microorganisms and their respective ecophysiological clusters across the three bioclimates. The results indicate that the microbiomes involved in SR can vary according to the bioclimatic conditions of the grape-growing area. Further research is required to comprehend the ecological requirements of these microorganisms, define their ecological niches to understand their geographical distribution and epidemiology, and enhance SR management strategies.