Salicornia bigelovii is a promising halophytic cash crop that grows in seawater of the intertidal zone of the west-north coast of the UAE. This study assess plant growth promoting (PGP) capabilities of halotolerant actinobacteria isolated from rhizosphere of S. bigelovii to be used as biological inoculants on seawater-irrigated S. bigelovii plants. Under laboratory conditions, a total of 39 actinobacterial strains were isolated, of which 22 were tolerant to high salinity (up to 8% w/v NaCl). These strains were further screened for their abilities to colonize S. bigelovii roots in vitro; the most promising ones that produced indole-3-acetic acid, polyamines (PA) or 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase (ACCD) were selected for rhizosphere-competency under naturally competitive environment. Three outstanding rhizosphere-competent isolates, Streptomyces chartreusis (Sc), S. tritolerans (St), and S. rochei (Sr) producing auxins, PA and ACCD, respectively, were investigated individually and as consortium (Sc/St/Sr) to determine their effects on the performance of S. bigelovii in the greenhouse. Individual applications of strains on seawater-irrigated plants significantly enhanced shoot and root dry biomass by 32.3-56.5% and 42.3-71.9%, respectively, in comparison to non-inoculated plants (control). In addition, plants individually treated with Sc, St and Sr resulted in 46.1, 60.0, and 69.1% increase in seed yield, respectively, when compared to control plants. Thus, the synergetic combination of strains had greater effects on S. bigelovii biomass (62.2 and 77.9% increase in shoot and root dry biomass, respectively) and seed yield (79.7% increase), compared to the control treatment. Our results also showed significant (P < 0.05) increases in the levels of photosynthetic pigments, endogenous auxins and PA, but a reduction in the levels of ACC in tissues of plants inoculated with Sc/St/Sr. We conclude that the consortium of isolates was the most effective treatment on S. bigelovii growth; thus confirmed by principal component and correlation analyses. To this best of our knowledge, this is the first report about halotolerant rhizosphere-competent PGP actinobacteria thriving in saline soils that can potentially contribute to promoting growth and increasing yield of S. bigelovii. These halotolerant actinobacterial strains could potentially be exploited as biofertilizers to sustain crop production in arid coastal areas.

中文翻译：

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耐盐海洋根际放线菌利用海水灌溉促进海蓬子生长和种子生产。

海蓬子是一种很有前途的盐生经济作物，生长在阿联酋西北海岸潮间带的海水中。本研究评估了从 S. bigelovii 根际分离的耐盐放线菌的植物生长促进 (PGP) 能力，将其用作海水灌溉 S. bigelovii 植物的生物接种剂。在实验室条件下，共分离出39株放线菌，其中22株能够耐受高盐度（高达8% w/v NaCl）。进一步筛选这些菌株在体外定殖 S. bigelovii 根的能力；选择最有前途的产生吲哚-3-乙酸、多胺（PA）或1-氨基环丙烷-1-羧酸（ACC）脱氨酶（ACCD）的酶来评估自然竞争环境下的根际能力。分别对三种出色的根际活性菌株：Chartreusis Streptomyces Chartreusis (Sc)、S. tritolerans (St) 和 S. rochei (Sr) 产生生长素、PA 和 ACCD 进行了单独和联合体 (Sc/St/Sr) 的研究，以确定它们对温室中 S. bigelovii 性能的影响。与未接种的植物（对照）相比，在海水灌溉植物上单独施用菌株可显着提高地上部和根干生物量，分别提高 32.3-56.5% 和 42.3-71.9%。此外，与对照植物相比，单独用 Sc、St 和 Sr 处理的植物种子产量分别增加了 46.1%、60.0 和 69.1%。因此，与对照处理相比，菌株的协同组合对 S. bigelovii 生物量（地上部和根干生物量分别增加 62.2% 和 77.9%）和种子产量（增加 79.7%）具有更大的影响。我们的结果还表明，接种 Sc/St/Sr 的植物组织中光合色素、内源生长素和 PA 的水平显着增加（P < 0.05），但 ACC 的水平降低。我们得出的结论是，分离菌群是对 S. bigelovii 生长最有效的治疗方法；从而通过主成分分析和相关分析得到证实。据我们所知，这是第一份关于耐盐根际活性 PGP 放线菌在盐渍土壤中繁衍生息的报告，该放线菌可能有助于促进 S. bigelovii 的生长和增加产量。这些耐盐放线菌菌株有可能被用作生物肥料，以维持干旱沿海地区的作物生产。