Exploring the beneficial interactions between plant and endophytes could be an effective strategy in the implementation of sustainable agricultural practices to enhance crop productivity. In this study, we aimed to evaluate holistically the plant growth promoting (PGP) abilities rendered by seed-transmitted endophytic bacteria isolated from in vitro grown calli of two rice cultivars. Nine bacterial endophytes, designated as PB001-PB009, were isolated and identified at the genus level through 16S rRNA gene sequence analysis. Biochemical investigations disclosed that they possess several PGP traits, such as phosphate solubilization, indole acetic acid biosynthesis, ammonia production, nitrogen fixation, amylase production and siderophore production. Results in gnotobiotic conditions revealed an increase in fresh weight, dry weight, root length and shoot length of seedlings germinated from endophyte-primed seeds than the control (uninoculated) set in a non-host and two host rice cultivars. In net house experiments, plants germinated from Micrococcus sp. PB001, Pseudomonas sp. PB002, Methylobacterium sp. PB005 and Methylorubrum sp. PB009 primed seeds showed an increase of upto 34.06 %, 38.77 %, 182.87 %, 16.59 % and 33.52 % in chlorophyll content, number of tillers/plant, number of grains/plant, grain size and grain weight, respectively than control plant sets in the non-host rice cultivar, further validating inter-cultivar PGP abilities of these endophytes. Metabolite profiling unfolded the abundance of few metabolites that are involved in pathways associated with PGP traits, in seedlings germinated from the endophyte-primed seeds. Together, the study documents the effect of seed-transmitted endophytic bacteria on intra- and inter-cultivar PGP by modulating certain sets of metabolites in rice plant, and is promising in developing bioinoculant formulations employing these selected endophytes for enhancement of rice productivity.

探索植物与内生植物之间的有益相互作用可能是实施可持续农业实践以提高作物生产力的有效策略。在这项研究中，我们旨在全面评估由两个水稻品种的离体愈伤组织分离的种子传播的内生细菌所产生的植物生长促进（PGP）能力。通过16S rRNA分离并鉴定了9种细菌内生菌，命名为PB001-PB009基因序列分析。生化研究表明，它们具有几种PGP特性，例如磷酸盐增溶，吲哚乙酸的生物合成，氨的产生，固氮，淀粉酶的产生和铁载体的产生。优生条件的结果表明，与在非宿主和两个宿主水稻品种中设置的对照（未接种）相比，由内生植物引发的种子发芽的幼苗的鲜重，干重，根长和苗长增加。在网房实验中，从Micrococcus sp。萌发的植物。PB001，假单胞菌属。PB002，甲基杆菌属。PB005和甲基橡胶sp。PB009引发的种子的叶绿素含量，分till /株数，籽粒/株数，籽粒大小和粒重分别比对照植物高出34.06％，38.77％，182.87％，16.59％和33.52％。非寄主水稻品种，进一步验证了这些内生植物的品种间PGP能力。在由内生菌引发的种子发芽的幼苗中，代谢物谱分析揭示了少数与PGP性状相关的途径中涉及的代谢物的丰富性。总之，该研究通过调节水稻植物中的某些代谢物，记录了种子传播的内生细菌对品种内和品种间PGP的影响，并且有望开发出利用这些选定的内生菌来提高稻米生产力的生物抑制剂配方。