Induction of Systemic Acquired Resistance in Cucumber Plant Against Cucumber Mosaic Cucumovirus by Local Streptomyces Strains

摘要

Nine Streptomyces strains were screened for their potential to protect Cucumis sativus from Cucumber Mosaic Virus (CMV). Foliage treatment with the Streptomyces culture filtrates resulted in 50-85% reduction of the mosaic symptoms. S. violatus, S. nasri H35, Streptomyces sp., S. aureofaciens and S. violaceuisniger showed the highest five antiphytoviral activities. The filtrate of the five Streptomyces strains showed more antiphytoviral activity when applied before virus inoculation compared to theirapplication after viral inoculation. The most favourable incubation period for the highest antiphytoviral activity detected in the filtrates were attained after incubation for 6 h. On the other hand, soaking of seeds for 2 h in the actinomycetes filtrates resulted in the highest viral inhibition, although there is no direct relationship between the percentage of inhibition and the time of soaking. Generally, S. violaceusniger filtrate recorded the highest percentage of viral inhibition (85%). Studies onthe ultrastructural changes in cucumber plants showed that viral inoculation led to distortion of spongy and vascular bundle cells as a results of presence of large vacuoles inside these cell. Treatment of inoculated cucumber plants with either Streptomyces strains gave a moderate recovery of cells.