Desert Plant Seed Endophytes: A Reservoir of Stress-Adapted Bacillus Strains for Enhancing Wheat Salinity Tolerance

Land desertification poses a major ecological challenge and threatens agricultural productivity. This study investigated the seed endophytic microbiomes of desert plants as a potential resource for mitigating salt stress in crops. Using high-throughput sequencing, we characterized the bacterial and fungal communities within seeds of 12 desert plant species. Dominant taxa included <i>Firmicutes</i> (particularly <i>Bacillus</i>), <i>Bacteroidota</i>, <i>Proteobacteria</i>, <i>Ascomycota</i>, and <i>Basidiomycota</i>. Culturable bacteria were subsequently isolated from <i>Haloxylon ammodendron</i> (C.A.Mey.) Bunge (HB) and <i>Hedysarum scoparium</i> Fisch. & C.A.Mey. (HSA) seeds. These isolates were screened for plant growth-promoting (PGP) traits and tolerance to salt (NaCl) and alkali (NaHCO₃). Selected strains, including the high indole-3-acetic acid (IAA)-producing <i>Bacillus</i> sp. HB-4, were used to inoculate wheat (<i>Triticum aestivum</i> L.) under 150 mM NaCl or 150 mM NaHCO₃ stress. Inoculation with strain HB-4 significantly improved wheat growth under stress. This improvement was associated with increased chlorophyll and proline content, enhanced activities of the antioxidant enzymes catalase and peroxidase, and reduced levels of malondialdehyde, a marker of oxidative damage. Our results demonstrate that desert plant seeds harbor taxonomically distinct and functionally resilient endophytes. The successful application of a desert-adapted <i>Bacillus</i> strain to alleviate salt stress in wheat highlights the potential of such microbiomes as a novel source of inoculants for sustainable agriculture in saline-affected regions.