Rhizosphere associated bacteria trigger accumulation of terpenes in leaves of Vitis vinifera L. cv. Malbec that protect cells against reactive oxygen species.

It has been proposed that plant growth promoting rhizobacteria (PGPR) stimulate plant growth and development by inducing the biosynthesis of secondary metabolites, like terpenes, which reduce stress incidence. Three bacteria previously isolated from grapevine roots and adjacent soil (Microbacterium imperiale Rz19M10, Kocuria erythromyxa Rt5M10 and Terribacillus saccharophilus Rt17M10) were tested as PGPR. After 30 days since root inoculation of in vitro grown Vitis vinifera cv. Malbec plants, the monoterpenes α-pinene, terpinolene and 4-carene, and the sesquiterpene nerolidol were detected only in bacterized-plant leaves. Also, the concentrations of the diterpenes α and γ-tocopherol, and the sterols sitosterol and lupeol were significantly enhanced compared to controls. The leaf extracts of bacterized plants showed photoprotective properties since they decreased the oxygen consumption (that is photo-oxidation) of the amino acid tryptophan in a sensitized solution, thus indicating an increment of the antioxidant capacity of the tissues. In addition, experiments with α-pinene and nerolidol standards showed the capability to intercept reactive oxygen species in the sensitized solution. Moreover, bacterized plants infected with the pathogen Botrytis cinerea showed a reduction in the lesion diameter compared with non-bacterized plants. The results suggest that M. imperiale, K. erythromyxa and mainly T. saccharophilus are able to induce a systemic response that trigger increases on monoterpenes, sesquiterpenes, tocopherols and membrane sterols. These compounds enhance the antioxidant capacity in leaf tissues that may help grapevine to cope with stresses.