Efficacy of Plant Growth-Promoting Rhizobacteria, Acibenzolar-<i>S</i>-Methyl, and Soil Amendment for Integrated Management of Bacterial Wilt on Tomato

Abstract

Greenhouse experiments were conducted to study the effect of plant growth promoting rhizobacteria (PGPR; Bacillus pumilus SE 34, Pseudomonas putida 89B61, BioYield, and Equity), acibenzolar-S-methyl (Actigard), and a soil amendment with S-H mixture (contains agricultural and industrial wastes such as bagasse, rice husk, oyster shell powder, urea, potassium nitrate, calcium super phosphate, and mineral ash) on bacterial wilt incidence caused by Ralstonia solanacearum (race 1, biovar 1) in susceptible tomato (Lycopersicon esculentum cv. Solar Set). In experiments with PGPR, Pseudomonas putida 89B61 significantly reduced bacterial wilt incidence when applied to the transplants at the time of seeding and 1 week prior to inoculation with Ralstonia solanacearum. BioYield, a formulated PGPR that contained two Bacillus strains, decreased disease significantly in three experiments. Equity, a formulation containing more than 40 different microbial strains, did not reduced wilt incidence compared with the untreated control. With inoculum at low pathogen densities of 1 × 10 5 and 1 × 10 6 CFU/ml, disease incidence of Actigard-treated plants was significantly less than with nontreated plants. This is the first report of Actigard-mediated reduction of bacterial wilt incidence in a susceptible tomato cultivar. When PGPR and Actigard applications were combined, Actigard plus P. putida 89B61 or BioYield reduced bacterial wilt incidence compared with the untreated control. Incorporation of S-H mixture into infested soil 2 weeks before transplanting reduced bacterial wilt incidence in one experiment. Combination of Actigard with the S-H mixture significantly reduced bacterial wilt incidence in tomato in two experiments.