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Erythrina velutina (\"mulungu\") is a legume tree from Caatinga that associates with rhizobia but the diversity and symbiotic ability of \"mulungu\" rhizobia are poorly understood. The aim of this study was to characterize \"mulungu\" rhizobia from Caatinga. Bacteria were obteined from Serra Talhada and Caruaru in Caatinga under natural regeneration. The bacteria were evaluated to the amplification of nifH and nodC and to metabolic characteristics. Ten selected bacteria identified by 16S rRNA sequences. They were tested in vitro to NaCl and temperature tolerance, auxin production and calcium phosphate solubilization. The symbiotic ability were assessed in an greenhouse experiment. A total of 32 bacteria were obtained and 17 amplified both symbiotic genes. The bacteria showed a high variable metabolic profile. Bradyrhizobium (6), Rhizobium (3) and Paraburkholderia (1) were identified, differing from their geographic origin. The isolates grew up to 45 °C to 0.51 mol L-1 of NaCl. Bacteria which produced more auxin in the medium with l-tryptophan and two Rhizobium and one Bradyrhizobium were phosphate solubilizers. All bacteria nodulated and ESA 90 (Rhizobium sp.) plus ESA 96 (Paraburkholderia sp.) were more efficient symbiotically. Diverse and efficient rhizobia inhabit the soils of Caatinga dry forests, with the bacterial differentiation by the sampling sites.

The Eriotheca gracilipes (K. Schum.) A. Robyns) is a forest specie that belongs to the Bombacaceae family and is considered an endemic specie from the Brazilian savanna. The aim of this study was to evaluate the best substrate and temperature for the vigor and germination test of E. gracilipes seeds. The experiment was carried out in a randomized design with a 4 x 7 factorial, with 28 treatments with the combination of four temperatures (20; 25; 30 and 20-30 °C) and seven substrates (coarse vermiculite, medium vermiculite, sand, Basaplant®, paper towel, on and between filter papers), with 4 repetitions of 25 seeds each. It was assessed germination, first count of germination, and germination speed index. In conclusion, for germination and vigor tests of Eriotheca gracilipes seeds it is recommended the paper roll as substrate at temperatures of 20-30, 25 or 30 °C, and the Basaplant® and paper roll at the temperature of 30 °C, respectively.

Microbial inoculants containing plant-growth-promoting bacteria (PGPB) are low-cost tools to improve crop yield. The prospection of new strains should enable the selection of efficient microbial agents for commercial inoculants. This study aimed to isolate and select PGPB for maize in the Brazilian semiarid region. A field trial using two maize genotypes was implemented, and bacteria were isolated from maize stems and roots. The bacteria were grown in semi-solid BMGM or solid Dyg’s media, and they were characterized in vitro with respect to five plant growth-promoting mechanisms. Twenty-seven strains were assessed for growth promotion using potted maize plants. Nine bacterial strains improved plant biomass and/or N accumulation in shoots and were selected for field assessment and identification by 16S rRNA sequencing. Fourteen and 65 bacterial strains were isolated, respectively, in the semi-solid and solid medium. Auxin production without L-Tryptophan and antagonism against F. verticillioides were found for bacteria isolated on solid medium, and other characteristics were found for the strains from semi-solid medium. These strains were classified as Bacillus (5), Brevibacillus (2), Staphylococcus (1), and Paenibacillus (1). Five strains ( Bacillus spp. ESA 593, ESA 597, ESA 599, ESA 600, and Paenibacillus sp. ESA 601) improved maize yield (56–87%) compared with the non-inoculated and non-fertilizated (N) control. In conclusion, the Brazilian drylands maize plants harbor several potential PGPB, and five elite strains were retrieved in the present study. These strains will be used for future network field assays to assure their agronomic performance.