The Root Microbiome of <i>Salicornia ramosissima</i> as a Seedbank for Plant-Growth Promoting Halotolerant Bacteria

• Main Authors: Maria J. Ferreira, Angela Cunha, Sandro Figueiredo, Pedro Faustino, Carla Patinha, Helena Silva, Isabel N. Sierra-Garcia
• Format: Article
• Language: English
• Published: MDPI AG 2021-03-01
• Series: Applied Sciences
• Subjects: halophytes; phytobiome; rhizosphere; endophytic bacteria; saline stress
• Online Access: https://www.mdpi.com/2076-3417/11/5/2233

Root−associated microbial communities play important roles in the process of adaptation of plant hosts to environment stressors, and in this perspective, the microbiome of halophytes represents a valuable model for understanding the contribution of microorganisms to plant tolerance to salt. Although considered as the most promising halophyte candidate to crop cultivation, <i>Salicornia ramosissima</i> is one of the least-studied species in terms of microbiome composition and the effect of sediment properties on the diversity of plant-growth promoting bacteria associated with the roots. In this work, we aimed at isolating and characterizing halotolerant bacteria associated with the rhizosphere and root tissues of <i>S. ramosissima</i>, envisaging their application in saline agriculture. Endophytic and rhizosphere bacteria were isolated from wild and crop cultivated plants, growing in different estuarine conditions. Isolates were identified based on 16S rRNA sequences and screened for plant-growth promotion traits. The subsets of isolates from different sampling sites were very different in terms of composition but consistent in terms of the plant-growth promoting traits represented. <i>Bacillus</i> was the most represented genus and expressed the wider range of extracellular enzymatic activities. Halotolerant strains of <i>Salinicola</i>, <i>Pseudomonas</i>, <i>Oceanobacillus</i>, <i>Halomonas</i>, <i>Providencia</i>, <i>Bacillus</i>, <i>Psychrobacter</i> and <i>Brevibacterium</i> also exhibited several plant-growth promotion traits (e.g., 3-indole acetic acid (IAA), 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, siderophores, phosphate solubilization). Considering the taxonomic diversity and the plant-growth promotion potential of the isolates, the collection represents a valuable resource that can be used to optimize the crop cultivation of <i>Salicornia</i> under different environmental conditions and for the attenuation of salt stress in non-halophytes, considering the global threat of arable soil salinization.