Efficiency of Some Bio-control Agents and Plant Extracts Against Beans (Phaseolus vulgaris L.) Damping-off and Root Rot diseases under Greenhouse and Field Conditions

Abstract

Damping-off and root-rot diseases in bean caused by Rhizoctonia solani Kuhn are considered the most destructive diseases. Rhizoctonia solani isolates were pathogenic and varied in their virulence on bean plants (Nebraska cv.) in vivo. The isolate No. 7 of R. solani obtained from Sakhawas the most aggressive one, which gave the highest percentages of pre- and post-emergence damping-off (66.7 and 26.7%), respectively. All Bio-agents viz. Trichoderma harzianum, T. aureoviride, Bacillus subtilisand B. amyloliquefaciens, plant extracts of garlic, onion and neem, biocides viz. Bio-Arc and Bio-Zeidin addition to chemical fungicide (Rizolex-T as positive control) were evaluated against bean damping-off and root-rot diseasesin vitro and in vivo. All tested antagonistic fungal and bacterial bioagents and plant extracts at different concentrations significantly reduced the linear growth of R. solani in vitro and decreased the incidence of R. solani damping-off and root-rot diseases under greenhouse and field conditions.Trichoderma harzianum, T. aureovirideandB. subtiliswere the most effective bio-agent, whilegarlic and onion at 5 and 7% concentration were the most effective plant extracts against damping-off and root-rot diseasesmeanwhile, B. amyloliquefaciens and neem extract were the lowest effective treatments compared to the control treatment. Under field conditions during the 2019 and 2020 growing seasons, all tested treatments significantly reduced damping-off, root-rot diseases and increased the percentage of survived plants as well as improved bean plant growthparameters (plant height, number of branches/plant), yield and yield components (No. of pods/plant, weight of pods/plant and 100 seed weight) compared to the control treatment. Also, the effects of antagonistic bioagents, plant extracts at 5%, biocides and chemical fungicide on the activity of lytic enzymes (β-1,3-glucanase and protease) and oxidative enzymes (peroxidase and polyphenoloxidase) were determined in the leaves of bean plant.