Biological Control of Sclerotinia sclerotiorum the Causal Agent of Potato White Mold by Different Trichoderma spp. and Coniothyrium minitans

The identity of outbreak of stem drying and early death on potato in vast area of potato fields of Hamedan province was studied. As a result، the causal agent of the disease was isolated and identified as Sclerotinia sclerotiorum. Considering the serious damage of this pathogen that can not be easily controlled by cultural and chemical control methods، alternative approaches such as biocontrol method using five species of Trichoderma including T. ceramicum، T. koningii، T. koningiopsis، T. virens، T. viridescens and one isolate of Coniothyrium minitans were evaluated against this pathogen. All mentioned biocontrol agents caused some control on the pathogen in vitro. In assessment of the effect of volatile metabolites on pathogen growth rate، the most inhibition percent was realized about T. koningiopsis with 56% and in case of extracellular compounds، the most inhibition percent in concentrations of 15 and 30% were showed T. ceramicum as 69% and 53%، respectively. In dual culture، T. koningiopsis، T. viridescens and T. ceramicum prevented sclerotia formation as such. They also grew and sporulated on the pathogen mycelia. In assessment of the affect of spore suspension of the biological agents on myceliogenic germination of sclerotia، the most inhibition was observed in T. ceramicum and T. koningiopsis and the less inhibition was in T. virens and Coniothyrium minitans. T. ceramicum، T. koningiopsis and T. viridescens are recently described Trichoderma spp. and this study is the first assessment of their biocontrol effect on plant diseases in Iran.