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

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

La Falda

Workshop; II Workshop Latinoamericano sobre PGPR; 2014

UNRC - UNQui - Univ. Antioquia

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. ln the frame of our studies on the microbiotaassociated to Medicogo spp. we studied and characterized bacterial isolates present within surfacesterilized alfalfa seeds (and within derived young plants) to investigate their diversity and activitiesassociated to the promotion of plant growth. M. sotivo (alfalfa) and M. truncotula seeds from 6different varieties were surface-sterilized using either sulfuric acid (98% P/P,LA min) or NaCIO (9 gCl2/1, tO min). After washing and neutralization, exudates obtained from these seeds in sterile PBSduring 4 h were plated in LB medium to isolate culturable bacteria. ln parallel, alfalfa plants wereobtained from the same surface-sterilized seeds; and grown in a plant chamber within sterile tubeswith vermiculíte and cotton caps to preserve sterility along the experiment. One month old plantswere harvested and milled in a sterile mortar with PBS. The resulting solution was also plated in LBmedium.Bacterial diversity was studied by: a) partial sequencing of 165 rDNAs, and b) analysis ofwhole-bacteria MALDI-TOF mass spectra. The bacterial collection originated from the seeds wasfinally characterized to investigate activities associated to plant growth promoting activities (i.ephosphate 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 bacterialgenera- was obtained from the surface sterilized seeds and their plants. lnterestingly, 8 of theidentified bacterial genera were recovered both from the exudates and as plant endophytes. Thisresult strongly suggests that bacteria from the seeds are source of early plant colonizingmicroorganisms. Remarkably, out of t2O isolates studied, 74 presented activities associated to thepromotion of plant growth, thus being suitable candidates to be tested in plant assays as bacterialinoculants.