Non-halophilic endophytes associated to the euhalophyte Arthrocnemum macrostachyum and their plant growth promoting activity potential

Abstract

Numerous microbial taxa establish natural relations with plants, and especially endophytes can be relevant in the development and growth promotion of their host. In this work we explore the diversity of non-halophilic microorganisms inhabiting the endosphere of the halophyte Arthrocnemum macrostachyum.A total of 1,045 isolates were recovered using standard non-saline media, which clustered into 22 operational phylogenetic units (OPUs) including seven putative new species and thirteen OPUs not previously detected as endophytes. The more abundant isolates corresponded to close relatives of Kushneria indalinina/K. marisflavi, Providencia rettgeri, Pseudomonas zhaodongensis and Bacillus safensis, which made up to ∼ 62% of the total isolates. We also isolated OPUs not detected by the culture-independent approach reinforcing the need of culturing to reveal the microbial diversity associated to plants. Additionally, the plant growth promoting activity was evaluated by representative strains of the more abundant OPUs (total = 94 strains) including also some previously isolated halophiles from the same plants. Under both saline and non-saline conditions, some strains principally those affiliated to Paenibacillus borealis, Staphylococcus equorum, Salinicola halophilus and Marinococcus tarijensis, presented growth promoting activity in Arabidopsis thaliana, which was evaluated as an increment of weight and root length.