Biological control of Sclerotinia sclerotiorum (Lib) De Bary cause the cucumber white stem rot by rhizospheric Actinobacteria

Actinobacteria have attracted high interests as potential biocontrol agents due to their antagonistic properties against wide range of plant pathogens particularly fungi. Sclerotinia sclerotiorum (Lib) De Bary, the causal agent of cucumber white stem rot, is one of the most destructive phytopathogens throughout the world which has three important characters as wide host range, severe pathogenicity and prolonged survival of the Sclerotia in unfavorable environmental conditions. Considering the serious damage of this pathogen that cannot be easily controlled by chemical methods, alternative approaches such as biocontrol method using several species of actinobacteria were evaluated against this pathogen. Antifungal bioactivity of 109 isolates of actinobacteria collected from soils of Alborz province of Iran was investigated against S. sclerotiorum through agar dual culture bioassays. Among them, Streptomyces UTS13, UTS19 and UTS49 revealed reasonable inhibitory capabilities in dual culture procedure. In physiological studies the isolates showed enzymatic activities of chitinase, and protease. The results showed that UTS13 reduced the disease upto 50% in greenhouse conditions and significantly increased plant growth compared with the control. UTS13 isolate was identified with molecular features as Streptomyces albidoflavus UTS13. Future perspective includes production of commercial biocontrol products and resistant transgenic plants having antifungal properties originated from biologically active genes of S. albidoflavus UTS13. This investigation introduced S. albidoflavus UTS13 as an effective biological agent with wide spectrum of antagonistic activities against Sclerotinia sclerotiorum.