Endophytic diazotrophs native from tree species can produce phytohormones and promote corn germination

ARIAS, ANABELA; IPARRAGUIRRE, JULIA; MASCIARELLI, OSCAR; LUNA, MARÍA VIRGINIA

La Falda- Córdoba

Workshop; II Latin American PGPR Workshop. II Taller Latinoamericano Sobre Rizobacterias Promotoras del Desarrollo Vegetal; 2014

REDBIO

It is well known that bacteria inhabiting the rhizosphere establish a close relationship with plants, helping them to grow through various mechanisms. The group of beneficial microorganisms known as PGPR includes root-colonizing bacteria which significantly stimulate plant growth. Although they are also diazotrophic bacteria, their principal plant growth promoter mechanism is through phytohormone production. That is why these organisms have been the subject of study not only in soil microbiology, but also in developing commercial biological products. The aim of this work was to study the native diazotrophic bacteria from the rhizosphere of two forest tree species, and to test their capacity as plant growth promoters on maize. From a total of 15 strains of endophytic bacteria isolated from two tree species, 4 were selected based on their ability to produce phytohormones. The magnitudes of the bacterial populations were quantified by the method of colony forming units (CFU/ml) in M9 medium and biomass production by turbidimetry (OD at 600 nm). Seeds were inoculated at 250 ml/50 kg. 50 seeds were placed in trays to evaluate germination, while for growth assessment 3 seeds per pot were sown (5 pots per treatment) with two replicates per treatment. The parameters measured were germination, shoot and root length, shoot and root fresh and dry weight, after 20 days. Regarding the in vitro production of phytohormones, the selected strains produced mainly JA, GA3, AIA, SA, ABA, in different concentrations. The WP1 strain was the major producer of GA3, WW7 produced ABA, PTD1 produced IAA and JA, and WW5 strain was the major producer of SA. The process of germination was promoted in corn seeds treated with PTD1 and WW7 strains during the first 120 hours after the start of imbibitions. Treatment with the last two strains was most effective in promoting root development in maize seedlings, coinciding with their ability to synthesize IAA and ABA. The results indicate that these strains may be useful as plant growth promoters to be used as seed inoculants in corn. Those results lead us to potential that the plant host is the selective agent for predominant bacterial genera, which selects the partners from soils or seeds.