Biocontrol of Rhizoctonia solani in Tobacco (Nicotiana tabacum) Seed Beds Using Pseudomonas fluorescens

摘要

Pseudomonas fluorescens isolates were screened from the rhizosphere soil of tobacco-growing fields of Andhra Pradesh and Karnataka. Antagonistic activity of isolates was observed against Rhizoctonia solani. In order to obtain a fluorescent Pseudomonasstrain having capacity to reduce the disease symptoms produced by R. solani, six P. fluorescens strains with moderate and high fungal growth inhibition capacity were tested in vitro. Tobacco seed beds pre-inoculated with R. solani at 108 cfu mP1 concentration were treated with six promising isolates of P. fluorescens obtained from tobacco rhizosphere. Despite the differences found in the dynamics of colonization and colonization capacity, all evaluated strains induced tobacco growth and reduced diseasesymptoms produced by R. solani. Present investigation clearly indicates that establishment of P. fluorescens strains in tobacco rhizosphere is a feasible alternative for the management of R. solani symptoms. P. fluorescens when applied as a biocontrol agent on tobacco seed beds showed appreciable increase in the biometric parameters of tobacco seedlings.