In this study, six Trichoderma strains viz. Trichoderma virens IMI-392430, T. pseudokoningii IMI-392431, T. harzianum IMI-392432, T.
harzianum IMI-392433, T. harzianum IMI-392434 and T. viride FPDTV and one commercial formulation of Trichoderma (Bio derma) were evaluated alone and in combination with F. solani, to assay their efficacy in suppressing root rot disease and promoting growth and yield ofW. somnifera. A pot trial experiment was conducted at the forest protection division nursery, Bangladesh Forest Research Institute (BFRI), Chattogram, Bangladesh from July 2014 to December 2014. Application of T. harzianum IMI-392433 alone (T12) or in combination with F solani (T5) significantly (p = 0.05) decreased the area under disease progress curve (AUDPC) (300.9 and 52.4) compared to F. solani (Tl) treatment. The highest seed germination rate (90.4 %) and the highest growth and yield were also recorded in the same treatment; while F. solani treatment (Tl) alone significantly decreased these values. The correlation matrix showed that root yield of W. somnifera had significant and positive correlation with plant height (r = 0.734**), number of leaf (r = 0.725 **), number of primary branch (r = 0.863 **), number of secondary branch (r = 0.878**), fresh shoot weight (r = 0.749**), dry shoot weight (r = 0.708**), number of flower at maximum flowering time (r = 0.734**), number of pod (r = 0.774**), number of seed (r = 0.642**), hundred seeds weight (r = 0.688**), seed yield/plant (r =
0.817**), root length (r = 0.711**), root diameter (r = 0.970**) and fresh root weight (r = 0.819**). The significant and negative correlation (r = – 0.619 **) was observed with the root yield/plant and area under disease progress curve (AUDPC). These results revealed that T. harzianum IMI-392433 has growth promoting effects and this strain may be used as an effective biocontrol agent to control root rot disease of W. somnifera.