Bacillus strains with potential for growth promotion and control of white mold in soybean

Abstract

Plant growth-promoting rhizobacteria (PGPR) are known to stimulate the biocontrol of phytopathogenic bacteria and fungi, induce plant growth, and increase the yield of important economic crops. In this study, we evaluated in vivo, the ability of Bacillus strains to control soybean white mold disease and promote the growth of soybean plants under greenhouse conditions. Initially, 27 Bacillus strains were analyzed by PCR for the presence of genes encoding antimicrobial molecules, followed by in vitro tests of the positive strains against four phytopathogenic fungi, Sclerotinia sclerotiorum, Macrophomina phaseolina, Rhizoctonia solani, and Colletotrichum truncatum. The bacterial strains that returned positive results for antimicrobial genes were evaluated in vivo for their growth promoting capacity in soybean cultivars Potencia RR and M6210 IPRO, and white mold control in soybean plants. The results showed that eight strains presented the genes bamD, ituD, and fenF, while the bacAB gene was observed in 16 of all tested Bacillus strains. Brie y, the inoculation of the strain VBN02 in increased the fresh biomass of shoots and roots by 111.9% and 79.39% compared with the control. The greenhouse experiment showed that the inoculation of the strain VBN02 was the best treatment for increasing fresh shoot biomass of the soybean M6210 IPRO and Potencia RR cultivar in the single inoculation in relation to the control (111.9% and 103.57%, respectively). Co-inoculation of soybean inoculant and VBE01 was the superior treatment for increasing fresh shoot and root mass in both the cultivars. Two other strains, VBE05 and VBE01, reduced the disease progression of white mold by 39.1% and 37.5%, respectively. In conclusion, our results showed that the Bacillus strains have potential for biocontrol of white mold and for promoting the growth of soybean plants.