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Thirteen strains of Streptomyces were evaluated as potential biological agents for control of
fusarium wilt, caused by Fusarium oxysporum f. sp. melonis. Eight strains of Streptomyces were
obtained from soil surrounding roots of cucurbit plants in Varamin area and 5 strains obtained
from surroundng of roots of capsicum in a glasshouse. Both the dual culture and cellophane
overlay techniques indicated that all strains of Streptomyces tested, inhibited the growth of
F.oxysporum f. sp. melonis. The inhibition varied among strains of Streptomyces, ranging from
13.3 to 99%. Plant survival in pots whit the seed treated with mixing Streptomyces strains (in
treatments of Streptomyces alone (100%), Streptomyces+Pathogen (39.28%), healthy control
(100%)) was significantly greater than that in pathogen treated control ((0%). Population
changes in F. oxysporum f. sp. melonis as well as in Streptomyces were studied during the
glasshouse experiments.