Abundance and diversity of tomato rhizosphere microbes in different land uses and their effect on bacterial wilt disease in Uganda

Abstract

Agricultural production is associated with changes in microbial diversity. This often leads to microbial unevenness and multiplication of soil borne diseases such as wilts, which are tedious to control and trend managed through use of biocontrols. Microbiome composition and land use management have been mentioned as core factors in effectiveness of biocontrols. Therefore, this study determined the diversity and abundance of microbes in the tomato rhizosphere and its effect on severity and biocontrol of bacterial wilt disease in soils from different land uses . Tomatoes were grown in a screen house at Namulonge using unsterilized soils from cultivated, fallow and forest land use types and were inoculated with Ralstonia solanacearum (positive control) but also include a non-inoculated set (negative control). Four biocontrols were used namely; Bacillus subtilis, Bacillus amyloliquefaciens, Peanibacillus polymyxa and Stenotrophomonas rhizophila. Data were collected on plant growth and yield parameters, and bacterial wilt disease incidence. Rhizosphere microbiome data were obtained using amplicon sequencing. Results showed that B. subtilis and P. polymyxa increased plant height in all land use types. Biocontrols B. amyloliquefaciens and S.rhizophila resulted into the highest dry biomass in cultivated land use, B. amyloliquefaciens and P. polymyxa in fallow and P. polymyxa and B. subtilis in forest land use type. In cultivated land use, biocontrols B. amyloliquefaciens, B. subtilis and S. rhizophila reduced bacterial wilt incidence by 31 % and P. polymyxa by 28 %. Fallow land use type had the highest microbial diversity and forest land use had the highest microbial abundance. The major phyla were Proteobacteria, Actinobacteria and Acidobacteria in Forest, Fallow and cultivated land uses respectively. Bacillus and Paenibacillus bacteria were more abundant in cultivated while Stenotrophomonas bacteria were more abundant in forest land use type