Diversity of bacterial endophytes in 3 and 15 year-old grapevines of Vitis vinifera cv. Corvina and their potential for plant growth promotion and phytopathogen control.

This study represents the first investigation on ecology of endophytic bacteria isolated from 3 and 15 year-old vine stems of Vitis vinifera cv. Corvina. The analysis was performed by means of culture-dependent techniques. The obtained results showed that new grapevine endophytic genera are being discovered. Moreover, Bacilli and Actinobacteria are frequently isolated from 3 year-old plants, whereas Alpha- and Gamma- Proteobacteria classes are more prevalent in the 15 year-old plants. Shannon-Wiener (H) index and analysis of rarefaction curves revealed greater genus richness in young grapevine plants. Furthermore, results evidenced an increase of genotypic group number within specific genera (e.g., Rhizobium and Pantoea). Among isolated strains from 3 and 15 year-old stems, respectively, 34 and 39% produce siderophores; 22 and 15% secrete ammonia; 22 and 21% produce indole-3-acetic acid; 8.7 and 41% solubilize phosphate. Besides, two strains isolated from 15 year-old grapevines showed 1-aminocyclopropane-1-carboxylate deaminase activity. Antifungal activity analysis evidenced that two Bacillus strains possess growth antagonistic effect toward all the tested fungal strains. Therefore, the present study extends our knowledge of the diversity of the endophytic bacteria by providing new insights into the complexity of the grapevine microbiome.