A remarkable bacterial diversity, including more than hrenty distinct genera, is present within seeds of different Medicogo spp.

LÓPEZ, J. L.; PRINCIPE, A.; ALVAREZ, F.; SALAS, M, E.; LOZANO, M. J.; DRAGHI, W. O.; DEL PAPA, M.F.; JOFRE, E.; PISTORIO, M.; LAGARES, A.

La Falda

Workshop; II Workshop Latinoamericano de PGPR; 2014

Univ. Nac. de Rio IV - Univ. Nac. de Quilmes

The use of biofertilizers to increase crop yields is an -ecologically and economically sound- growing practice in agriculture. Microrganisms present in the rhizosphere and/or within the plants improve in many cases plant growth and plant health. ln the frame of our studies on the microbiota associated to Medicogo spp. we studied and characterized bacterial isolates present within surfacesterilized alfalfa seeds (and within derived young plants) to investigate their diversity and activities associated to the promotion of plant growth. M. sotivo (alfalfa) and M. truncotula seeds from 6 different varieties were surface-sterilized using either sulfuric acid (98% P/P,LA min) or NaCIO (9 g Cl2/1, tO min). After washing and neutralization, exudates obtained from these seeds in sterile PBS during 4 h were plated in LB medium to isolate culturable bacteria. ln parallel, alfalfa plants were obtained from the same surface-sterilized seeds; and grown in a plant chamber within sterile tubes with vermiculíte and cotton caps to preserve sterility along the experiment. One month old plants were harvested and milled in a sterile mortar with PBS. The resulting solution was also plated in LB medium.Bacterial diversity was studied by: a) partial sequencing of 165 rDNAs, and b) analysis of whole-bacteria MALDI-TOF mass spectra. The bacterial collection originated from the seeds was finally characterized to investigate activities associated to plant growth promoting activities (i.e phosphate solubilization; production of chitinases, siderophores, cellulases, indol acetic acid, proteases; and biocontrol tests). A collection of more than 150 different isolates -belonging to at least 20 different bacterial genera- was obtained from the surface sterilized seeds and their plants. lnterestingly, 8 of the identified bacterial genera were recovered both from the exudates and as plant endophytes. This result strongly suggests that bacteria from the seeds are source of early plant colonizing microorganisms. Remarkably, out of t2O isolates studied, 74 presented activities associated to the promotion of plant growth, thus being suitable candidates to be tested in plant assays as bacterial inoculants.