The Efficiency of Streptomyces antibiotics as a Biocontrol Agent for Damping Off Disease of Sunflower (Helianthus annuus)

In pot experiments, a local isolate of the Actinomycete Streptomyces was used as a biocontrol agent against Macrophomina phaseolina, the causative agent of damping-off in sunflowers (Helianthus annuus L.). Seeds and soil treatments with S. antibiotics resulted in a significant decrease in the percentage of infected plants. Disease severity of damping off of the seedlings reached (31%), As compared to untreated seeds planted in soil contaminated with M.phaseolina, which was(40.12%) and (0.40) respectively, However, seed treatment with the biocontrol agent was superior to soil treatments in causing more reduction in both percent infection and disease severity of seedlings damping off reached (20.63%) and (0.21) respectively, and also improving growth characters of the plants. The ability of S. antibiotics to produce the hormone (IAA) was confirmed, and IAA was separated and purified by TLC. Quantitative determination by HPLC showed that the IAA concentration was 7.59 mg/L.