Abstract
Bacterial endophytes, a subset of a plant’s microbiota, can facilitate plant growth by a number of different mechanisms. The aims of this study were to assess the diversity and functionality of endophytic bacterial strains from internal root tissues of native legume species grown in two distinct sites in South of Portugal and to evaluate their ability to promote plant growth. Here, 122 endophytic bacterial isolates were obtained from 12 different native legume species. Most of these bacteria possess at least one of the plant growth-promoting features tested in vitro, with indole acetic acid production being the most common feature among the isolates followed by the production of siderophores and inorganic phosphate solubilization. The results of in planta experiments revealed that co-inoculation of chickpea plants with specific endophytic bacteria along with N2-fixing symbionts significantly improved the total biomass of chickpea plants, in particular when these plants were grown under saline conditions. Altogether, this study revealed that Mediterranean native legume species are a reservoir of plant growth-promoting bacteria, that are also tolerant to salinity and to toxic levels of Mn. Thus, these bacterial endophytes are well adapted to common constraints present in soils of this region which constitutes important factors to consider in the development of bacterial inoculants for stressful conditions in the Mediterranean region.
Highlights
The internal biota that exists within plant tissues includes a diverse range of microbes that have a significant influence on many attributes of the plant’s growth and development
This study showed that Mediterranean native legume species harbor highly diverse endophytic communities in their root tissues and that most of these bacteria possess at least one plant growth-promoting feature, and are tolerant to salinity and to toxic levels of Mn
Legume species belonging to the genera Trifolium and Scorpiurus were exclusively found in the Herdade da Mitra site while the species Ornithopus sativus and Lupinus angustifolius were only found in the Alcácer do Sal site
Summary
The internal biota that exists within plant tissues includes a diverse range of microbes that have a significant influence on many attributes of the plant’s growth and development. These bacteria appear to play a key role in the normal as well as the stress functioning of host plants [2,3] In these plant-microbe interactions, the plant host provides diverse protective niches for endophytic organisms while endophytic bacteria can benefit the host plants through the production of phytohormones, such as indoleacetic acid (IAA) and cytokinin, which are responsible for plant growth, development and biomass [4], increasing the uptake of nutrients like phosphorous or nitrogen [5], induce resistance or suppress phytophatogens [6,7], and increase resistance to abiotic stresses [8,9,10]. Legumes are a key component of Mediterranean agro-ecosystems, both within the Mediterranean region as well as other regions of the world with a similar climate [14]
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