A remarkable bacterial diversity, including more than twenty distinct genera, is present withinseeds of differentMedicagospp.

LOPEZ, JL.; PRÍNCIPE , A.; ÁLVAREZ , F.; SALAS, ME.; LOZANO, MJ.; DRAGHI, WO.; DEL PAPA, MF.; JOFRE, E.; PISTORIO, M.; LAGARES, A.

La Falda, Córdoba, Argentina

Workshop; II Latin American PGPR workshop.; 2014

The use of biofertilizers to increase crop yields is an-ecologically and economically sound-growingpractice in agriculture. Microrganisms present in the rhizosphere and/or within the plants improvein many cases plant growth and plant health. In the frame of our studies on the microbiota associatedtoMedicagospp. we studied and characterized bacterialisolates present within surface-sterilizedalfalfa seeds (and within derived young plants) to investigate their diversity and activities associatedto the promotion of plant growth.M. sativa(alfalfa) andM. truncatulaseeds from 6 differentvarieties were surface-sterilized using either sulfuric acid (98% P/P, 10 min) or NaClO (9 g Cl2/l, 10min). After washing and neutralization, exudates obtained from these seeds in sterile PBS during 4 hwere plated in LB medium to isolate culturable bacteria. In parallel, alfalfa plants were obtained fromthe same surface-sterilized seeds; and grown in a plant chamber within sterile tubes with vermiculiteand cotton caps to preserve sterility along the experiment. One month old plants were harvestedand milled in a sterile mortar with PBS. The resulting solution was also plated in LB medium.Bacterialdiversity was studied by: a) partial sequencing of 16S rDNAs, and b) analysis of whole-bacteria MALDI-TOF mass spectra. The bacterial collection originated from the seedswas finally characterized toinvestigate 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 andtheir plants. Interestingly, 8 of the identifiedbacterial genera were recovered both from the exudates and as plant endophytes. This resultstrongly suggests that bacteria from the seeds are source of early plant colonizing microorganisms.Remarkably, outof 120 isolates studied, 74 presented activities associated to the promotion of plantgrowth, thus being suitable candidates to be tested in plant assays as bacterial inoculants.