The functional diversity of endophytic and rhizospheric microorganisms associated with the promotion of plant growth includes increased availability of plant nutrients, phytohormone synthesis and phytopathogen suppression. We used the hypothesis that the unknown root and rhizospheric community associated with the Butia purpurascens palm, an endemic species of the Cerrado, could be composed of microbiota with great functional diversity. Thus, the potential of the isolates of this community for four functional traits was evaluated: solubilization of calcium phosphate (CaHPO) and iron phosphate (FePO), synthesis of indoleacetic acid (IAA) and suppression of seed- and fruit-spoilage fungi of B. purpurascens. A total of 166 bacterial isolates, most belonging to the phylum Proteobacteria (94%), and 46 fungal isolates (Ascomycota) were tested. None of the isolates showed the four functional traits tested, but 72% presented two traits (CaHPO solubilization and IAA synthesis). Fifteen fungi (27% of the isolates) presented only the trace for IAA, whereas the capacity for antibiosis was observed in only eight bacteria. CaHPO-solubilization capacity was evidenced by all bacterial isolates and by some fungal isolates. The functional trait for IAA production was present in all isolates, and production levels were significantly above 100 μg mL for some bacteria. Isolates of the genus Bacillus efficiently suppressed the growth of spoilage fungi tested, with relative inhibition rates reaching levels higher than 60% when using Bacillus subtilis. These results attest to the multifunctionality of the endophytic and rhizospheric isolates of B. purpurascens for the promotion of plant growth. This is the first study that sought to identify the root endophytic and rhizospheric microbiota associated with the B. purpurascens palm for the bioprospection of species with functional traits related to the promotion of plant growth, thus opening the way for in vivo tests in plants of commercial or ecological interest.

Interactions between plants and microorganism are complex and can affect the establishment of plant communities and change ecosystem properties. These interactions are of interest for researchers and have many ecological and biotechnological applications. The present study is the first report on the microbial diversity associated with Butia purpurascens Glassman, and the goal was to isolate and identify the genetic diversity of endophytic and rhizospheric growable microorganisms from B. purpurascens using molecular biology techniques. Endophytic and rhizospheric microorganisms were isolated from the roots and rhizospheric soil of the purple yatay palm. DNA was extracted, and the 16S region for bacteria and internal transcribed spacer (ITS) region for fungi were amplified and sequenced. The resulting sequences were compared with known sequences from GenBank by similarity search using BLASTn. The rhizosphere and roots of B. purpurascens harbor a diverse set of microorganism groups. Fourteen (14) genera of endophytic and 12 genera of rhizospheric bacteria were identified that belonged to three phyla (Proteobacteria, Firmicutes and Actinobacteria), and 11 endophytic and six rhizospheric genera of fungi were identified that belonged to the phylum Ascomycota. The most frequent isolated genera were Enterobacter and Pseudomonas for endophytic bacteria, Gibberella and Codinaeopsis for endophytic fungi, Bacillus and Enterobacter for rhizospheric bacteria, and Ceratocystis for rhizospheric fungi. Differences were observed between the endophytic and rhizospheric microbial communities of B. purpurascens, with some microorganisms only detected in one environment. Further studies with a higher number of individuals are required to confirm these results.

The excessive use of agrochemicals negatively impacts the environment, making the development of sustainable technologies for the reduction of contaminants in soil necessary. Hexazinone is the herbicide most used for sugarcane crops and persists in the environment. Moreover, its main route of degradation in the soil is through microorganisms. Therefore, six microorganisms were selected that presented growth in the presence of the herbicide; SCR1 - Microbacterium arborescens; SCR2 - Bacillus pumilus; SCM3 - Stenotrophomonas maltophilia; SCM4 - Bacillus cereus; SCM5A - M. arborescens; and SCM5B - B. safensis. A test was performed to evaluate the ability of each lineage in phosphate solubilization. For the Ca3(PO4)2 solubilization test, the strains that showed the best results were B. pumilus and S. maltophilia. Subsequently, the inoculants were prepared and the concentrations after plating were 2.71 × 109 CFU mL-1 for B. pumilus, 1.02 × 109 CFU mL-1 for S. maltophilia, and 1.14 × 1010 CFU mL-1 for a combination of the two strains. These were satisfactory values for use as inoculants.

Field experiments testing the effect of phosphate-solubilizing rhizobacteria (PSRB) should consider the cropping history and the method used to inoculate the strains. We evaluated the hypothesis that PSRB previously isolated from soybean seedlings could be effective in promoting growth in this oilseed crop in soils with different cultivation periods. We also evaluated whether this growth promotion could be influenced by cultivation histories or the inoculation method (via seeds or soil). Thus, we conducted an experiment in five fields cultivating Glycine max during two seasons (2019/2020 and 2020/2021), to test the effectiveness of PSRB (SAF9-Brevibacillus sp., SAF11-Brevibacillus sp., and SAC36-Bacillus velezensis) compared with results observed for the inoculant BiomaPhos (mix of Bacillus subtilis and Bacillus megaterium). The present study was based on the evaluation of vegetative growth, nutritional and yield parameters, and microbial biomass carbon (MBC). PSRB were more effective than, or showed similar effectiveness to, BiomaPhos for most of the evaluated vegetative, nutritional, and yield characteristics. In the fields tested in the summer 2019/2020 crop, SAC36 and SAF9 strains stood out as growth promoters, whereas in the 2020/2021 crop, SAF11, SAC36, and BiomaPhos were notable. There did not seem to be a direct relationship between long histories of soybean cultivation as a monoculture and low yield in the field. However, yield seems to be associated with soil nutritional characters such as Ca, Mg, K, P, cation exchange capacity, and organic matter levels. PSRB inoculation positively affected nodulation (NN) and nodule dry mass (NDM) in the evaluated fields in the 2019/2020 crop, and the aerial part dry mass (APDM), NN, NDM, yield, and MBC of the evaluated fields in the 2020/2021 crop. In contrast, the inoculation method was observed to have a strong effect on APDM, NN, root dry mass, and MBC, as the plants inoculated via seed showed higher mean values than those in the plants inoculated via soil. This study demonstrated the growth-promoting potential of new phosphate-solubilizing strains, which may eventually be incorporated by the biostimulants market to freely compete with BiomaPhos.

Aloe verais among the world’s economically most important medicinal plants, but as the growth of this plant and, consequently, the accumulation of metabolites is slow, we tested the hypothesis that root endophytic bacteria isolated from A. veraplants can promote growth and increase the accumulation of aloin in the gel and latex. For this, we inoculate seedlings with four endophytic bacteria and a combination of them. We confirmed the hypothesis and identified two strains with potential for the formulation of inoculants to improve the cultivation of A. vera. The bacterium 149H Paraburkholderiasp. increases the number of leaves and the accumulation of biomass, but on the other hand, 35V Enterobacter ludwigiiinoculation increased the content of aloin in the gel and in the latex. Further research should focus on the association of these two strains in a single inoculant, to both promote growth and increase the synthesis of metabolites.