A total of 20 isolates of T. harzianum were screened
against R. solani to select the most effective biocontrol
agent. All the isolates were isolated from the rhizosphere
and rhizoplane soils of bean, rice, chilly, tomato, sun-
flower, strawberry, and wheat. The soil dilution plate
technique and root washing methods were used for
isolation of the fungus isolates [17]. In the dilution plate
technique, 10 g of composite soil collected from the
rhizosphere and the rhizoplane of the selected plant
species were taken in a 250-mL Erlenmeyer flask.
Sterilized water was added to flasks (100 mL/flask). The
flasks were agitated on a vortex for 2 min for thorough
mixing and 1-mL sub-samples were transferred fromeach flask to another one containing 9 mL of sterile water.
In this way, a 5-fold serial dilution of the soil suspension
was prepared. Then, 0.1 mL of each dilution was incorporated
into the PDA plate. The isolates of T. harzianum were
purified in acidified water agar using hyphal tip culture
technique; the cultures were maintained in PDA slants at
10 8C for further use