Efficacy of Bacillus spp. and Trichoderma harzianum against bacterial wilt of tomato

Bacterial wilt caused by Ralstonia solanacearum is considered as the most destructive disease of potato, tomato, chili and other members of solanaceous and musaceae family.Pathogen has worldwide distribution and also reported from Pakistan.In Past, different control strategies such as crop rotation, resistant cultivars, and pesticides opted but failed.Thus, this study was to look at the potential of indigenous biocontrol agents (BCAs) against R. solanacearum.Soil samples were obtained from the rhizosphere of asymptomatic solanaceous plantations.To isolate Bacillus spp., heated serial dilutions (60 o C) were plated and individual colonies were isolated.Dual culture assays revealed two putative bacterial isolates (AR and NSR) showing percent growth inhibition against R. solanacearum.Bacillus subtilis, Trichoderma harzianum also inhibited the growth of R. solanacearum whereas Bacillus thuringenesis was unable to restrict the growth of R. solanacearum.Moreover, NSR and Bacillus subtilis showed compatibility with T. harzianum.In a pot experiment, tomato roots were pierced prior to inoculation with individual and consortia of biocontrol agents (BCAs) by soil drenching method.Seven days of post inoculation with BCAs, tomato seedlings were challenged by R. solanacearum.The results revealed that both individual and consortia of BCAs minimized wilt compared to the positive control.This pilot study unraveled the efficacy of indigenous bacterial and fungal antagonists in controlling R. solanacearum which needed to be tested under field conditions.In future, BCA application not only act as bulwark against pathogens but will also be helpful in reducing the injudicious use of pesticides.