Changes in the production of molecular signals involved in the rhizobial colonization of legumes roots in plants inoculated with a microbial consortium

TONELLI MARIA LAURA; MAGALLANES NOGUERA CYNTHIA; FABRA ADRIANA

Cordoba

Congreso; XI CONGRESO ARGENTINO DE MICROBIOLOGÍA GENERAL; 2015

In previous studies we demonstrated that in peanut and soybean plantsinoculated with the microbial consortium composed by a biocontrol agent(Bacillus sp. CHEP5) and a microsymbiont (Bradyrhizobium sp. SEMIA 6144 orBradyrhizobium japonicum E109) in presence or absence of Sclerotium rolfsii andCercospora sojina, respectively, the symbiotic behavior of both microsymbiontswas improved. Moreover, the disease incidence or severity caused by the fungalpathogens was reduced when plants were inoculated simultaneously with themicrosymbiont and the biocontrol bacteria.Taking into account these results, the objectives of this work were a) to determine changes in the composition of flavonoids secreted by roots when the legumes grow in presence of fungal pathogens and beneficial bacteria, b) to evaluate the ability of bacterial mixed cultures to form biofilms.The flavonoids profiles from the legume root exudates were determined by HPLC.Preliminary results indicated differences in peanut root exudates composition,revealing an important production of daidzein and crysin in control plants.Meanwhile, in root exudates from plants inoculated with the microsymbiont or themicrobial consortium it was detected the production of genistein. In root exudates from soybean plants challenged with the pathogen it was detected the production of crysin and luteolin, while in those inoculated only with the microsymbiont or the microbial consortium it was identified crysin.On the other hand, results obtained from the in vitro biofilm formation assayrevealed that the bacterial consortium showed a greater biofilm formation indexcompared to pure microsymbiont culture. However, the biofilm formation index ofBacillus sp. CHEP5 growing in pure culture was higher than in mixed cultures.From these results it is suggested that legumes flavonoids production is affected by the presence of the microbial consortia. Moreover, the ability to form biofilms appears to be increased in bacterial mixed cultures, compared to microsymbionts pure cultures. Since the production of biofilm confers a greater capability to colonize plant roots, this could turn in higher root microsymbiont colonization, explaining the improved symbiotic behavior under this condition.