Rhizobia can colonize the roots of grasses in the Brazilian semiarid region; however, studies to isolate these bacteria for growth promotion of maize via unconventional isolation approaches have not been conducted. This study aimed to isolate, characterize (biochemically and molecularly) and assess the potential of cowpea nodulating/maize associated rhizobia for plant growth promotion. Extracts of surface-disinfected maize root were inoculated onto cowpea seeds in axenic conditions. Rhizobia were isolated and classified by sequencing of the 16 S rRNA and nodC genes, and recA and atpD were specifically assayed for Bradyrhizobium. The in vitro ability of rhizobia to produce auxin and siderophores, solubilize calcium phosphate, exhibit antagonism against the growth of the pathogen Fusarium verticillioides, and undergo endophytic colonization were evaluated. The ability of rhizobia to promote the growth of both potted cowpea and maize and to promote the growth and yield of maize under field conditions was also evaluated. Thirteen isolates were obtained, including six Rhizobium, four Agrobacterium, and three Bradyrhizobium isolates, which exhibited high genetic variability and low similarity with the type strains. All bacteria showed at least one plant growth promotion mechanism. Six bacteria stood out regarding the promotion of maize growth, and one bacterium showed the best performance in cowpea. The results of the field assay with maize indicated that Bradyrhizobium sp. ESA 114 and Rhizobium sp. ESA 116 induced the same maize grain yields as those observed in plants inoculated with the commercial strain of Azospirillum brasilense Ab-V5. Maize harbors a community of putative facultative endophytic rhizobia that are genetically diverse and have the potential to be used in inoculant production.

根瘤菌可以在巴西半干旱地区定居于草的根部。然而，尚未进行通过非常规分离方法分离这些细菌以促进玉米生长的研究。这项研究旨在分离，表征（生物化学和分子生物学）并评估of豆结节/玉米相关的根瘤菌对促进植物生长的潜力。在无菌条件下，将表面消毒的玉米根提取物接种到cow豆种子上。根瘤菌通过16 S rRNA和nodC基因测序分离和分类，并专门测定recA和atpD的根瘤菌。在体外评估了根瘤菌产生植物生长素和铁载体，溶解磷酸钙，拮抗病原性镰刀菌（Fusarium v​​erticillioides）生长并进行内生菌落定殖的能力。还评估了根瘤菌在田间条件下促进盆栽cow豆和玉米生长以及促进玉米生长和产量的能力。获得了13种分离株，包括6个根瘤菌，4个农杆菌和3个根瘤菌分离株，表现出高的遗传变异性和与菌株的相似性低。所有细菌均显示出至少一种植物生长促进机制。在促进玉米生长方面，有六种细菌脱颖而出，其中一种细菌在cow豆中表现最佳。玉米田间试验的结果表明，根瘤菌属属。ESA 114和根瘤菌sp。ESA 116诱导的玉米籽粒产量与在商业上接种巴西固氮螺旋体Ab-V5的植物中观察到的相同。玉米拥有一个推定的兼性内生根瘤菌群落，这些根瘤在遗传上是多样的，并且有可能被用于孕育剂的生产。