Impact of double inoculation with Bradyrhizobium japonicum E109 and Azospirillum brasilense Az39 on soybean plants grown under arsenic stress

ARMENDARIZ, ANA L.; TALANO, MELINA A.; OLMOS NICOTRA, MARÍA FLORENCIA; ESCUDERO, LETICIA; BRESER, MARÍA LAURA; PORPORATTO, CARINA; AGOSTINI, ELIZABETH

PLANT PHYSIOLOGY AND BIOCHEMISTRY

ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER

Año: 2019 vol. 138 p. 26 - 35

0981-9428

Inoculation practice with plant growth-promoting bacteria (PGPB) has been proposed as a good biotechnological tool to enhance plant performance and alleviate heavy metal/metalloid stress. Soybean is often cultivated in soil with high arsenic (As) content or irrigated with As-contaminated groundwater,which causes deleterious effects on its growth and yield, even when it was inoculated with rhizobium.Thus, the effect of double inoculation with known PGPB strains, Bradyrhizobium japonicum E109 andAzospirillum brasilense Az39 was evaluated in plants grown in pots under controlled conditions andtreated with As. First, the viability of these co-cultivated bacteria was assayed using a flow cytometryanalysis using SYTO9 and propidium iodide (PI) dyes. This was performed in vitro to evaluate thebacterial population dynamic under 25 μM AsV and AsIII treatment. A synergistic effect was observedwhen bacteria were co-cultured, since mortality diminished, compared to each growing alone. Indoleacetic acid (IAA) produced by A. brasilense Az39 would be one of the main components involved in B.japonicum E109 mortality reduction, mainly under AsIII treatment. Regarding in vivo assays, under Asstress, plant growth improvement, nodule number and N content increase were observed in doubleinoculated plants. Furthermore, double inoculation strategy reduced As translocation to aerial parts thusimproving As phytostabilization potential of soybean plants. These results suggest that doubleinoculation with B. japonicum E109 and A. brasilense Az39 could be a safe and advantageous practiceto improve growth and yield of soybean exposed to As, accompanied by an important metalloidphytostabilization.