BACTERIUM (Bacillus amyloliquefaciens) AS A BIOCONTROL AGENT AGAINST FUNGAL DISEASES OF SORGHUM

Abstract

Sorghum (Sorghum bicolor L.) is among the main primary foods in arid and semi-arid lands and it is grown for both food and also as a forage crop. Its production is constrained by both biotic and abiotic factors. To ensure continuous production this study aimed at addressing sustainable management strategies to foliar fungal diseases of sorghum in western parts of Kenya. The first section of the experiment was set under field conditions in different sites and seasons with an attempt of ascertaining the effects of Bacillus amyloliquefaciens bacterium on incidences of foliar diseases on selected sorghum genotypes. This study was set in split plot arrangement under Randomized Complete Block design with genotypes as the main plot and treatments as the subplots replicated thrice. The second experimental phase aimed at determining the inhibitory potentials of the strains of Bacillus amyloliquefaciens on single fungal pathogens isolated in vitro. The study design involved the use of three replicating in a randomized complete block study design. The experiment was followed by a greenhouse experiment that tested the effectiveness of different concentrations of the bacterium in treating sorghum covered -kernel disease. Randomized complete block trial was also conducted using different rates of inoculation of Bacillus amyloliquefaciens. Field, lab, and greenhouse research was performed separately to assemble data. Field trials were used to record instances and the degree of sorghum foliar diseases. The percentage of mycelial inhibition in the laboratory acted as the main indicator whereas the percentage of the greenhouse was converted to the percentage of coveredkernel disease severity. The statistical processes employed to analyze all the data collected were done through the use of GENSTAT software, version 14 and the results were presented within the form of plates, figures, tables and box-and-whisker groupings. It was found that three foliar diseases (anthracnose, leaf spot and leaf blight) occurred in both sites through two seasons. The reasons were that the outbreak and severity of anthracnose were significantly more in Kibos than Sega. Varieties did not show a significant difference in their tolerance to disease pressure (p > 0.05) while treatments displayed a distinct efficacy in reducing disease pressures compared to control (p <0.05) where dressing seeds with bacterium proved to be more efficient in managing foliar diseases. Treatments with Bacillus amyloliquefaciens recorded an improved plant growth and reduced disease severity and the response was directly proportional to increase in rates of the bacterium. Bacillus amyloliquefaciens bacterium is a growth enhancer and also reduces disease severities and therefore should be incorporated into integrated disease management system to ensure sustainable crop production. Further studies should be conducted to characterize genetic compositions of genotypes with respect to treatments that will aid in further crop improvement.