Endophytic actinomycetes of cucumber:isolation,antagonistic activity and identification

The aim of the study is screening anti-microorganism endophytic actinomycetes for plant disease control.The results showed that 77 strains of endophytic actinomycetes were isolated from roots,stems and leaves of cucumber seedlings.Seventy two percent of endophytic actinomycete strains were isolated from roots,the quantity and variety of which were much higher than those from strems and leaves.Most of the isolates were Streptomyces(cluster: lavendularectus and griseofuscus).Antagonistic activities of the endophytic actinomycetes against 12 pathogenic fungi and 6 bacteria strains were tested in vitro.The strains with antifungal and antibacterial activity were 46.8% and 39.0%,respectively,which were mainly isolated from roots and belonged to lavendularectus of Streptomyces.Furthermore,the cell-free filtrate of fermentation broth of strain gCLA4 isolated from leaves of cucumber seedling,showed notable inhibition effect on 12 pathogenic fungi and most tested bacteria strains.Identification of strain gCLA4 by morphological,cytochemical characters and 16S rDNA sequence showed it belonged to Streptomyces lavendularectus.