Interaction of different biocontrol agents and PGPR bacteria with other beneficial microorganisms in the development of leguminous plants

LEÓN, MARIANA; ANTHERO DE MIRANDA TEIXEIRA, R; YARYURA, PABLO; SAGGIN JÚNIOR, ORIBALDO J.; RIBEIRO DA SILVA, ELIANNE M,; STRALIOTTO, R.; CORREA, OLGA S.; KERBER, NORMA L.; PUCHEU, NORMA L.

Rosario, Santa Fe, Argentina

Congreso; V Congreso Argentino de Microbiología General,; 2008

SAMIGE

Abstract Side effects cause by the introduction of biocontrol agents to the soil was evaluated. Compatibility with other beneficial microorganisms and possible synergistic effects on the development of soybean (Glycine max L Merril) and common bean (Phaseolis vulgaris L.) were evaluated. Co-inoculation with biocontrol agents (BA), arbuscular mycorrhizal fungi (AMF) and nitrogen fixing bacteria (NFB) was carried out. A total of five strains were used in this study: Bacillus amyloliquefaciens BNM122, Pseudomonas fluorescens BNM296, Bacillus cereus BNM343, Burkholderia cepacia BNM345 (Banco Nacional de Microorganismos, IBYF-CONICET, Argentina), and Burkholderia brasiliensis M130-BR11340 (Agrobiología collection, Embrapa, Brasil). Assays were carried out in pots filled with tyndalized soil. Treatments consisted on individual inoculation of pre-germinated seeds (root:1.5 cm) with each one of the five selected strains. At sowing time, inocula of AMF (Gigaspora margarita plus Glomus clarum), plant specific NFB (Rhizobium etli BR322-BR520 for bean or Bradyrhizobium japonicum BR29-BR96 for soybean) were added to all pots. Plants were grown for 60 days in a greenhouse under controlled conditions. The registered and analyzed parameters were: fresh and dry weigh of aerial biomass, plant height at 30 and 60 days after sowing, mycorrhizal colonization, mycorrhizal spore number (MSN) and the number and weigh of nodules. In bean plants the treatment with strain BNM345 showed an increase of 53 and 66 % in fresh and dry weigh of plants compared with the non-inoculated control. No differences were found in the rest of treatments and parameters measured. In soybean plants despite no differences in aerial biomass were registered, the inoculation with BNM345 increased the MSN and also the number and weigh of nodules. Also, strain BNM343 increased the MSN although a reduction in the fresh weigh of nodules was observed as occurred in the rest of the treatments. Strain BNM343 deserves further studies in order to verify its positive effect on mycorrhization, a well known PGPR mechanism. Inoculation with strain BNM345 showed a beneficial effect for the two leguminous plants, suggesting a direct stimulation in both AM and NFB colonization. Inoculation with the other bacterial strains did not report any beneficial effect on none of the two leguminous plants and in addition, the soybean nodulation was reduced.