Background As a polymicrobial disease, grape sour rot can lead to the decrease in the yield of grape berries and wine quality. The diversity of microbial communities in sour rot-infected grapes depends on the planting location of grapes and the identified methods. The east coast of China is one of the most important grape and wine regions in China and even in the world.
Methods To identify the pathogenic microorganism s causing sour rot in table grapes of eastern coastal areas of China, the diversity and abundance of the bacteria and fungi were assessed based on two methods, including traditional culture-methods, and 16S rRNA and ITS gene high-throughput sequencing . Then the pathogenicity of cultivable microorganisms was determined in laboratory.
Results Based on traditional culture-methods, we identified 15 cultivable bacterial species and 10 fungal species from sour rot-infected grapes. The p athogenicity assay confirmed five cultivated fungi species (three Aspergillus species, Alternaria tenuissima, and Fusarium proliferatum), and four bacteria species (two Cronobacter species, Serratia marcescens and Lysinibacillus fusiformis) as mainly pathogenic on grape. A. tenuissima, and F. proliferatum were the firstly discovered as pathogens on harvesting grape. Moreover, high-throughput sequencing revealed the OTUs numbers of bacteria and fungi were 1343.33 and 1038.67 respectively. Proteobacteria (72.15%) and Firmicutes (26.83%) were dominant phylums among the 19 bacterial phyla identified, while Ascomycota (93.86%) was the dominant fungal phylum. Then, bacteria such as Acetobacter sp., Gluconobacter sp., Bacillus sp., and Lactococcus sp. and fungi such as Incertae sedis sp., Issatchenkia terricola, Colletotrichum viniferum, Hanseniaspora vineae, Saprochaete gigas, and Candida diversa took the vast majority ofmicrobial species in sour rot-infected grapes. Therefore, more accurate and abundant microbial communities in sour rot-infected grapes could be identified using the traditional culture-methods and high-throughput sequencing.