Interactions Between Vascular Arbuscular Mycorrhizal Fungi And Streptomyces As Biocontrol Agent For Tomato Damping-Off Disease Caused By Rhizoctonia SolaniKuhn

The most popular and important plant Lycopersicon esculentum Mill or Tomato was attacked by several fungal pathogens and several biocontrol agents can be used. Mycorrhizal fungi are mutuality associated with many plant rootswhile actinomycete isolates of the genus Streptomyces enhanced plant growth and decreased plant pathogen development. Thus, interaction between Mycorrhizae and Streptomyces has been attracting attention due to the excellentbenefitto the plantsby decreasing fungal infectionand damping-off disease caused by Rhizoctonia solani. Out of 4 isolates of R. solani, the most pathogenic isolatewas R. solani LB4 (% of plant survival, 30%), thus it was selected for more detail study. From rhizosphere soil of tomato,15 actinomyceteisolates were obtained. The 15 isolates in addition to Streptomyces exfoliates LP10 were screened for inhibitory effect against R. solani. Out of the 15 isolates, 6 were inhibitory forR. solaniusing agar disc diffusion method but thehighest diameters of the inhibition zone (27 mm) was forStreptomyces exfoliates LP10. Production of varying levels of growth hormone (IAA) and lytic enzymes (Chitinase and β-1,3 Glucanase)by Streptomycesisolates were also determined and S. exfoliates LP10 was the most active isolate, thus it was selected in addition to mycorrhizal fungi for antifungal activity against R. solaniLN4 on infected tomato plants. Plant fungal infection by R. solani LN4 decreased the numbers of the survived plants to 30%. Fungal infection decreased plant growth and mineral contents in 2 months old tomato plants. Proline was enhanced in diseased plants and decreased by the presence of biochontrol agents. Inoculation with biochontrol agents enhanced seedling growth, biomass of shoot and root after 2 months after infection with R. solani LB4 which may be attributed to hormone (IAA) and lytic enzymes (Chitinase and β-1,3 Glucanase) production by theStreptomyces isolate or the antagonistic activity and enhancing phosphorus uptake by mycorrhizal fungi. In conclusion it can be revealed that mycorrhizal fungi, S. exfoliates LP10 or their interactions effectively reduced R. solani LP4 infectionon tomato roots under in vivo conditions and in whole fungal infection was significantly reduced by the used biocontrol treatments. The findings from this study clearly indicated the possibilities of using mycorrhizal fungi associated with actinomycete isolates as bio-inoculums for growth promotion and biocontrol of fungal infections of tomato.