Burkholderia spp. as potential antagonistic to Rhizoctonia solani AG-1 IA on soybean seeds

Soybean crops are affected by various diseases that cause significant economic damage. The fungus Rhizoctonia solani is among the phytopathogens that cause major harm to the crop, producing symptoms such as damping-off, root rot, hypocotyl rot, leaf blight, and aerial blight. Biological control offers a sustainable alternative by providing antagonism to pathogenic microorganisms. The bioprospecting of bacteria isolated from extreme environments, such as mangroves, has been minimally explored, even though it could improve the chances of finding strains with high biotechnological potential. This study aimed to isolate bacterial from mangrove soils and assess their potential for controlling R. solani AG-1 IA in soybean seeds. Soil samples were collected from the coasts of the Brazilian states of São Paulo and Rio de Janeiro and taken to the laboratory for bacterial isolation. Initially, a screening of the strains was performed in vitro by direct confrontation with R. solani in Petri dishes. Of the 157 bacteria isolated, only five were selected for the in vivo assay, as they showed high levels of inhibition of R. solani AG-1 IA at low concentrations. The efficacy of the strains in controlling R. solani was determined using two inoculation methods: soaking and coating the soybean seeds in the bacterial growth culture. Application of Burkholderia cepacia, and B. glumae by soaking the seeds in bacterial cultures showed better results compared to seed coating, significantly reducing disease severity. In greenhouse conditions, B. cepacia PR10 was more effective in controlling the phytopathogen and also stimulated the development of soybean plants. In conclusion, B. cepacia, and B. glumae emerged as potential antagonists for controlling R. solani AG-1 IA.