Bacterial species causing leaf and fruit spots and stem lesions of grapevine (Vitis vinifera L.) in Iran

Grapevine (Vitis vinifera L.) is one of the most economically important and widely cultivated fruit crops worldwide. In the summers of 2018 and 2019, a new disease of grapevine was observed in vineyards of Bojnurd (North Khorasan province) and Gorgan (Golestan province) in Iran. The affected grapevines displayed cankerous lesions on the stems, sunken spots on the fruit, and irregular, dark-brown spots surrounded by a yellow halo on the leaves. A total of 40 infected samples yielded 45 bacterial isolates, which revealed two distinct groups: 18 isolates with creamy colonies and 27 isolates with yellow colonies. Based on the colony morphology, phenotypic and pathogenicity features, as well as analysis of 16S rRNA and housekeeping genes sequences the isolated strains were identified as Pseudomonas viridiflava and Pantoea agglomerans. To confirm the disease-causing ability of the isolates, grapevine seedlings and detached fruits were inoculated. The isolates reproduced the symptoms and were re-isolated from the inoculated plants, thus proving their pathogenicity. To the best of our knowledge, this is the first report worldwide of the occurrence of leaf and fruit spots and stem lesions of grapevine caused by P. viridiflava and P. agglomerans.