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.