Isolation and characterization of endophytic Streptomyces strains from surface-sterilized tomato (Lycopersicon esculentum) roots.
OBJECTIVE
To isolate endophytic Streptomyces strains from tomato and examine their antimicrobial activity.


METHODS
Endophytic Streptomyces strains were isolated using surface-sterilization methods and identified by morphological characteristics. Antimicrobial activities were measured by the agar plate sensitivity method. Antifungal activity in vivo was measured by seedling mortality in infested soils.


RESULTS
Twenty-one per cent of endophytic streptomycete isolates produced antibacterial metabolites and 41% produced antifungal metabolites in S medium. Sixty-five per cent of the most frequently isolated strains inhibited the growth of Rhizoctonia solani by the antibiosis assay but only 32% produced metabolites active against R. solani in S medium. Growth promotion and enhanced disease resistance of seedlings inoculated with Streptomyces sp. strain S30 were observed in tomato but not in cucumber seedlings.


CONCLUSIONS
Endophytic Streptomyces spp. strains were successfully isolated using stringent methods and strain S30 promoted growth and enhanced resistance to R. solani in tomato seedlings.


CONCLUSIONS
Endophytic streptomycetes showing antifungal activity in vitro and in vivo may indicate the potential for their use as biocontrol agents particularly of R. solani disease of tomato seedlings.
State Key Laboratory for Biocontrol and Department of Biochemistry, School of Life Sciences, Zhongshan (Sun Yatsen) University, Guangzhou 510275, P.R. China.
L
L
Cao
Z
Z
Qiu
J
J
You
H
H
Tan
S
S
Zhou
D000900:Anti-Bacterial Agents / Q000096:biosynthesis / Q000494:pharmacology; D000898:Antibiosis; D001419:Bacteria / Q000187:drug effects / Q000254:growth & development; D002681:China; D018553:Cucumis sativus / Q000382:microbiology; D005658:Fungi / Q000187:drug effects / Q000254:growth & development; D018551:Solanum lycopersicum / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D010572:Pest Control, Biological / Q000379:methods; D018517:Plant Roots / Q000382:microbiology*; D012232:Rhizoctonia / Q000187:drug effects / Q000254:growth & development; D036226:Seedlings / Q000382:microbiology; D013242:Sterilization; D013302:Streptomyces / Q000302:isolation & purification* / Q000502:physiology*
D000900:Anti-Bacterial Agents