Biostimulation of beneficial bacteria in the rhizosphere of Solanum tuberosum

N-acylhomoserine lactones (NAHL) are signal molecules synthesized by several phytopathogenic bacteria. In Pectobacterium carotovorum, the virulence on potato plants and tubers is modulated by such signals. The inactivation of NAHL signals therefore permits to reduce the aggressiveness of the bacterial pathogen, hence the severity of the disease symptoms. One of the antivirulence strategies investigated in our laboratory consists in the application of gamma-caprolactone (GCL) to stimulate the growth of indigenous, NAHL-degrading bacteria in the rhizosphere of Solanum tuberosum. When this treatment was applied to hydroponic cultures of S. tuberosum in green houses for tuber production, a significant increase of the ratio of NAHL-degrading bacteria among total cultivable bacteria was observed in several independent experiments and the implicated bacteria belonged to the Rhodococcus and Delftia genera. This work highlights the opportunity to manage the NAHL-degrading bacteria in a complex environment such as rhizosphere.