Salt stress affects plant growth and crop yield reduction, thus how to improve the salt tolerance of plants is full of challenges. Plant growth-promoting rhizobacteria (PGPR), as an environment-friendly treatment to improve salt stress tolerance of plants is widely accepted and has big potential in field application. In this study, a halotolerant actinomycete Streptomyces sp. KLBMP5084 obtained from the root of halophyte Limonium sinense was evaluated for antifungal activity in vitro and applied for the growth promoting of tomato seedlings under salt stress. Results demonstrated that the fermentation broth and the volatile organic compounds (VOCs) of strain KLBMP5084 could inhibit a variety of plant pathogenic fungi, including tomato early blight disease pathogenic fungi Alternaria solani. In particular, the KLBMP5084 inoculation significantly enhance the growth of tomato seedlings compared with the control after irrigating with 200 mM NaCl, with increased fresh weight, shoot length, and the number of fibrous roots. Further, the antioxidant enzymes activity, soluble sugar and proline contents in leaf and stem were also effectively increased, and malondialdehyde (MDA) was decreased. KLBMP5084 inoculation also increased the contents of K⁺ and Ca²⁺, reduced the Na⁺ accumulation in leaf. A total of 191 genes were also observed differentially expressed after KLBMP5084 treatment under salt stress in leaves by transcriptome analysis. Genes involved in the photosynthesis-antenna proteins pathway, isoquinoline alkaloid biosynthesis, zeatin biosynthesis and protein processing of endoplasmic reticulum pathway were enriched to the highest degree, indicating their significance and effects in response to salt stress in tomato seedlings. Collectively, these findings indicate that strain Streptomyces sp. KLBMP5084 has the potential as the biological fertilizer for promoting the tomato seedlings growth under salinity stress.

盐胁迫影响植物的生长和农作物减产，因此如何提高植物的耐盐性充满了挑战。促进植物生长的根际细菌（PGPR）作为一种提高植物耐盐性的环境友好处理方法已被广泛接受，在野外应用中具有巨大潜力。在这项研究中，卤虫放线菌链霉菌属。从盐生植物柠檬草的根中获得的KLBMP5084在体外评估了抗真菌活性并用于盐胁迫下促进番茄幼苗的生长。结果表明，菌株KLBMP5084的发酵液和挥发性有机化合物（VOCs）可以抑制多种植物病原真菌，包括番茄早疫病病原真菌Solnaria solani。特别地，与用200 mM NaCl灌溉后的对照相比，接种KLBMP5084可以显着增强番茄幼苗的生长，同时增加了鲜重，枝条长度和纤维根的数量。此外，叶和茎中的抗氧化酶活性，可溶性糖和脯氨酸含量也得到有效提高，丙二醛（MDA）降低。接种KLBMP5084也会增加K ⁺和Ca ^2+的含量，减少了叶片中Na ^+的积累。通过转录组分析，还观察到在盐胁迫下在叶中经KLBMP5084处理后共有191个基因差异表达。参与光合作用-天线蛋白质途径，异喹啉生物碱合成，玉米素生物合成和内质网途径蛋白质加工的基因被高度丰富，表明它们在番茄幼苗中响应盐胁迫的意义和作用。总的来说，这些发现表明菌株Streptomyces sp。KLBMP5084有潜力作为生物肥料来促进盐胁迫下番茄幼苗的生长。