Efficacy of combine use of biocontrol agents on control of Sclerotium rolfsii and Rhizoctonia solani of Capsicum annuum.

摘要

Rhizobacteria Pseudomonas fluorescens CA05, Pseudomonas putida CA28 and Bacillus subtillis CA32 which showed antagonism in a Petri plate assay were tested singly and in combination for their biological control efficacy against Rhizoctonia solani and Sclerotium rolfsii under greenhouse conditions. The bacteria were applied to the seeds before seeding and to the root system prior to transplanting. Two disease assessment criteria were used in this study. All bacterial treatments significantly decreased the disease severity of C. annuum observed up to 30 days after transplanting and the magnitude of the protection was similar when assessed in terms of number of plants which remained healthy during the experimental period. Combining B. subtillis with either Pseudomonads strains gave enhanced control. However, the combined application of two Pseudomonads strains did not improve the plant protection. When the plants were assessed by using a stem-lesion index, none of the Pseudomonads strains either alone or in combination significantly protected the plants from the both pathogens. But the application of B. subtilis alone and in combination with either Pseudomonads strains exerted biocontrol. The R. solani and S. rolfsii populations were dramatically reduced after 30 days of transplanting in bacterial treated pots compared to the controls indicating the biocontrol ability of these rhizobacteria. Therefore, the results show that a combination of B. subtilis with Pseudomonads strains can lead to greater plant protection against R. solani and S. rolfsii than the biocontrol exhibited by these strains used separately. Because of the results observed in this study the importance of disease assessment criteria in evaluating biological control agents is emphasized.