Bacillus velezensis strain Ag75 as a new multifunctional agent for biocontrol, phosphate solubilization and growth promotion in maize and soybean crops

Abstract

Soybean and maize are some of the main drivers of Brazilian agribusiness. However, biotic and abiotic factors are of great concern, causing huge grain yield and quality losses. Phosphorus (P) deficiency is important among the abiotic factors because most Brazilian soils have a highly P-fixing nature. Thus, large amounts of phosphate fertilizers are regularly applied to overcome the rapid precipitation of P. Searching for alternatives to improve the use of P by crops is essential to reduce the demand for P input. The use of multifunctional rhizobacteria can be considered one of these alternatives. In this sense, the objective of the present work was to select and validate bacterial strains with triple action (plant growth promoter, phosphate solubilizer, and biocontrol agent) in maize and soybean, aiming to develop a multifunctional microbial inoculant for Brazilian agriculture. Bacterial strains with high indole acetic acid (IAA) production, phosphate solubilization, and antifungal activity against soil pathogenic fungi (Rhizoctonia solani, Macrophomina phaseolina, and Fusarium solani) were selected from the maize rhizosphere. Then, they were evaluated as growth promoters in maize under greenhouse conditions. Based on this study, strain 03 (Ag75) was selected due to its high potential for increasing biomass (root and shoot) and shoot P content in maize. This strain was identified through genomic sequencing as Bacillus velezensis. In field experiments, the inoculation of this bacterium increased maize and soybean yields by 17.8 and 26.5%, respectively, compared to the control (25 kg P2O5). In addition, the inoculation results did not differ from the control with 84 kg P2O5, indicating that it is possible to reduce the application of phosphate in these crops. Thus, the Ag75 strain has great potential for developing a multifunctional microbial inoculant that combines the ability to solubilize phosphate, promote plant growth, and be a biocontrol agent for several phytopathogenic fungi.

Identification of bioactive compounds of Bacillus velezensis HNA3 that contribute to its dual effects as plant growth promoter and biocontrol against post-harvested fungi

“…Our results are in accordance with previous reports that Bacillus species particularly Bacillus velezensis strains have potential plant growth-promoting activity ( 55 ). Growth of soybean plants promoted after inoculating with Bacillus velezensis Ag75 ( 19 ) Bacillus velezensis S141 improved soybean growth and stimulated nodulation in the root ( 56 ). In addition, Bacillus velezensis CMRP 4490 enhanced the growth of soybean plants and improved seed germination ( 57 ).…”

“…This bacterium allocates the majority of its gene clusters toward the synthesis of diverse bioactive compounds ( 17 ). This genetic propensity underpins its multi-functional characteristics, granting it a wide array of beneficial functions ( 19 ). Bacillus licheniformis K11 inhibits the growth of phytopathogen Phytophthora sp., enhances the growth of pepper plants and produces indole acetic acid (IAA) and lytic enzymes ( 20 ).…”

“…Bacillus licheniformis K11 inhibits the growth of phytopathogen Phytophthora sp., enhances the growth of pepper plants and produces indole acetic acid (IAA) and lytic enzymes ( 20 ). Bacillus velezensis Ag75 multi-functional agent promotes maize and soybean growth, solubilizes phosphate, and suppresses the growth of pathogenic fungi including Rhizoctonia solani , Fusarium solani , and Macrophomina phaseolina ( 19 ). Bacillus sp.…”

Transcriptome profiling of genes regulated by phosphate-solubilizing bacteria Bacillus megaterium P68 in potato (Solanum tuberosum L.)

“…PSB could increase the effective phosphorus in the soil and be of help in plant uptake, thus promoting plant growth. Mosela et al (2022) applied PSB, increased yields by 17.8% in maize and 26.5% in soybean. Zaheer et al (2019) isolated PSAZ17 from sandy soil and applied it to chickpea field experiment, compared with CK, it could increase grain yield by 1,127 kg·ha −1 and increase phosphorus content in grain by 25.69%.…”

Large effect of phosphate-solubilizing bacteria on the growth and gene expression of Salix spp. at low phosphorus levels

“…Bacillus spp. are well-known and well-documented PSM and have been tested many times for their use as potential biofertilizers of crop plants ( Tahir et al., 2018 ; Ahmad et al., 2019 ; Miljaković et al., 2020 ; Mosela et al., 2022 ). In the present experiment, among the 15 most effective strains that solubilized phosphates, Bacillus spp.…”