The search for sustainable agriculture has increased interest in using endophytic bacteria to reduce fertilizer use and increase stress resilience. Stress-adapted plants are a potential source of these bacteria. Some species of these plants have not yet been evaluated for this, such as pangolão grass, from which we considered endophytic bacteria as potential plant growth promoters. Bacteria from the root, colm, leaves, and rhizospheric soil were isolated, and 132 strains were evaluated for their in vitro biological nitrogen fixation, IAA and siderophores production, and phosphate solubilization. Each mechanism was also assessed under low N availability, water stress, and low-solubility Fe and P sources in maize greenhouse experiments. All strains synthesized IAA; 63 grew on N-free media, 114 synthesized siderophores, and 46 solubilized P, while 19 presented all four mechanisms. Overall, these strains had better performance than commercial inoculant in all experiments. Still, in vitro responses were not good predictors of in vivo effects, which indicates that the former should not be used for strain selection, since this could lead to not testing strains with good plant growth promotion potential. Their heterologous growth promotion in maize reinforces the potential of stress-adapted plant species as potential sources of strains for inoculants.

Semiarid-adapted species often harbor endophytic populations that help mitigate host plant stress. Thus, we evaluated the diversity and plant growth-promoting potential of endophytic bacteria from highly drought-resistant (HDR) (Opuntia undulata, O. stricta, and O. ficus-indica) and less-drought-resistant (LDR) (all O. cochenillifera) forage cactus cultivars. Purified isolates were characterized using BOX-PCR and grouped into 186 strains. We investigated the presence of acdS and nifH, indole-3-acetic acid (IAA), siderophore production, calcium phosphate solubilization, and osmotic stress adaptation in vitro, and these characteristics led to 25 groups at 100 % similarity. Representatives from each group were sent for 16S sequencing. Of the 186 strains, 24 were positive for acdS, 41 for nifH, 30 produced IAA, 75 produced siderophores, 15 solubilized phosphorus, and 66 supported at least one level of osmotic stress. Twelve genera were identified with 95-100 % identicality to the NCBI gene bank, including Acinetobacter, Bacillus, Burkholderia, Citrobacter, Desertihabitans, Enterobacter, Leclercia, Priestia, Pseudomonas, Ralstonia, Staphylococcus, and Stenotrophomonas. The HDR group had a higher proportion of acdS- and nifH-positive strains and more in vitro growth-promoting mechanisms. Although these results indicate a higher occurrence of bacteria with potential stress-reduction effects in the more resistant genotypes, this must be confirmed in plants under stressful environments.