Abstract: Trichoderma strains effectively controlling the seedling blight of Panax quinquefolium L. were screened using dual-culture antagonistic activity assay and a plot experiment and identified by internal transcribed spacer (ITS) sequence analysis and morphological characteristics. The result showed that all test Trichoderma strains could inhibit R. solani on a PDA plate, among which strain HB20111 had the highest inhibition ratio of 99.33%. In the plot experiment, strain HB20111 significantly controlled the seedling blight of P. quinquefolium L., with a significant difference compared to other treatments (P<0.05). For seed dressing used in the first year, the control efficiency, weight gain rate of a single plant and weight gain rate of total plants reached 71.81%, 33.54% and 92.75%, respectively.And for root adhesion treatment in the second year, the values of the three parameters were 91.04%, 158.06% and 1369.34%, respectively. The strain HB20111 was identified as T. atroviride, with typical single branched conidiophores as its other morphological characteristics were consistent with T. atroviride and ITS sequence was 100.0% homologous with that of T. atroviride. HB20111 is expected to substitute chemical fungicide in the production of P. quinquefolium L. due to fast growth, strong sporulation ability, and high control efficiency.

Key words: Trichoderma artroviride HB20111, Panax quinquefolium L., seedling blight, control efficiency, species identification