Isolation, Characterization and Selection of Bacteria that Promote Plant Growth in Grapevines (Vitis sp.)

Certain bacteria can promote and stimulate plant growth, increasing the production of biomass and reducing damage caused by phytopathogens. With that in mind, this research effort set out to select these plant growth-promoting bacteria in order to evaluate their effects on the growth of grapevines (Vitis sp.). The bacteria were isolated from several vineyard soil samples, and evaluated based on their production of IAA (Indole-3-Acetic Acid), siderophores and cellulase, as well as their phosphate solubilization and nitrogen fixation capabilities. In vivo testing included six separate treatments with the following bacterial isolates- C12, O7, B3, I3, a control group and a blended group. The tests were performed in a greenhouse with bacterial suspension inoculation placed around the roots of Paulsen 1103 rootstock cuttings. The data collected included the following- number of leaves per plant, branch lengths, chlorophyll content, fresh and dry mass, and Carbon, Hydrogen, Nitrogen and Sulfur concentrations. Forty-six separate bacteria were isolated, of which 100% produced IAA, 65.21% produced siderophores, 63.04% solubilized phosphate, 34.78% produced cellulase, and 30.43% showed nitrogen fixation. The in vivo testing also revealed significant increases in the length of the branch and in percentages of Carbon and Nitrogen. The C12 isolate exhibited the highest increase in branch length (76.704 cm), whereas the O7 and C12 were identified as Bacillus amyloliquefaciens and Bacillus thuringiensis, respectively.