Plant Growth-Promoting Bacteria Associated to the Halophyte Suaeda maritima (L.) in Abbas, Iran

Abstract

Suaeda maritima (L.), regarded as a promising halophyte, is widely distributed along the coastal plains of Abbas, Iran. Suaeda maritima has been highly incorporated with the traditional agriculture to support the Iranian agricultural economy. However, its productivity is limited by a lack of available nitrogen. Application of halotolerant plant growth-promoting rhizobacteria (PGPR) suggested being an alternative biological fertilizer. Increasing the knowledge of halotolerant PGPR associated to the native crops remains important. Nine endemic colonies were isolated from the roots of S. maritima. Those isolates were cultured in different salinity conditions (0, 0.25, 0.5, and 0.75 M NaCl) and maintained at different temperature regimes (30 and 55 °C). The nitrogen fixation ability of the isolated endemic colonies was screened by acetylene reduction assay. Among them, only one showed high acetylene reduction activity and capacity to solubilize phosphates. This bacterium was identified as Bacillus amyloliquefaciens. Seeds inoculated with Bacillus amyloliquefaciens, in conjunction with Azospirillum halopraeferens as a biological control, were tested for seed germination and early growth promotions of S. maritima exposed to high salinities under in vitro conditions. Bacillus amyloliquefaciens showed a high specificity for the wild S. maritima. This is the first report of Bacillus amyloliquefaciens as nitrogen-fixing bacterium associated with the oilseed S. maritima a novel halophyte crop. Through this work, a reliable biological method was found, based on beneficial bacteria, to contribute to maintain or improve the fertility of soils sustaining Suaeda fields.