SCREENING OF BACTERIA ISOLATED FROM THE SOIL FOR BIOCONTROL

ABSTRACT

Biological control applies to the use of microbial antagonists to suppress diseases as well as the use of host specific pathogens. Insecticides, fungicides, herbicides, rodenticides, and plant growth regulators are typical examples of plant disease control agents, many of the chemicals have been associated with health and environmental issues and the agricultural use of certain chemical has been abandoned. This study aimed at screening bacteria isolated from the soil for biocontrol potentials against selected pathogens. Six bacteria were isolated from selected agricultural soils in Benin City, Edo State (Sporasarcina spp, Micrococcus spp, Proteus spp, Alcaligens spp, Bacillus spp (2) and Micrococcus spp) and tested for their antagonistic effect against bacteria isolated from diseased Manihot esculenta leaf (Erwnia spp, Enterobacter hormaechei S36-2, Enterobacter ludwigii GM7, Xanthomonas spp and Bacillus spp). The antibacterial activity was performed using agar well diffusion method, in which different concentrations (25%, 50% and 100%) of the various cell filtrates from the farm were tested against the isolated bacteria pathogen from diseased Manihot esculenta leaf. From the results, most of the potential biocontrol bacterial isolates did not display biocontrol activities against the selected pathogens at lower concentrations, however, at 100% concentration all potential antagonistic bacteria except Bacillus sp (1) displayed antagonism against the pathogens with zones of inhibition ranging from 0.03±0.00 cm to 1.38±0.01cm this was however significantly different from the positive control, Chloramphenicol (0.90±0.45 - 4.90±2.45 cm). This study revealed that most of the bacterial isolates displayed positive potential for antagonism against the pathogens isolated from diseased Manihot esculenta leaf at the highest concentration (100%). More studies should however be conducted to enhance the antangonistic potential of these organisms and determine the applicability and of this findings in vivo and safety of the isolates to plant and human health.