Señales producidas por Rhizobium leguminosarum en la interacción con frijol común (Phaseolus vulgaris L.) SIGNALS PRODUCED BY Rhizobium leguminosarum IN THE INTERACTION WITH COMMON BEAN (Phaseolus vulgaris L.)

Legume-Rhizobium interaction depends on a complex signal exchange that continues throughout the entire symbiotic process, out of which just the correct combination will give rise to an efficient symbiosis. These plants secrete flavonoids that are recognized by compatible bacteria inducing their nod genes, which encode proteins that synthesize and export lipochitooligosaccharides called Nod factors. These factors activate infection process and initiate cell division in the root until making up the nodule and also participate in nitrogen biological fixation. There is evidence that the use of nod gene inducers increases some legume nodulation. The objective of this work was to study the production of some signal molecules induced by genistein isoflavon in a R. leguminosarum strain as well as to evaluate induction impact on inoculum effect upon common bean plants. Inoculum lipid fraction was isolated with n-butanol and analyzed by thin layer chromatography, high performance liquid chromatography and gas chromatography coupled to a mass spectrometer. Regarding the inocula induced with genistein, a higher amount of lipooligosaccharides (Nod factors) and high-molecular- weight fatty acids were detected, showing significant differences with non-induced controls. Concerning such signal molecule enrichment, genistein-induced inocula had a positive effect on "Cubacueto 25-9" bean plants, with a higher amount of nodules and chlorophyll content than non-inoculated plants (control).