Materials and methods
This study was conducted in the greenhouse (24 ± 2 °C). Thirty-day-old seedlings of tomato (cv. Sultana-7) were used, one seedling per pot (15 cm diam.). The soil of each pot (1500 g) was a mixture of sand, sandy loam and peat moss (2:1:1), which was previously steam-sterilized (15 Psi at 121 °C) with an autoclave for 30 min.
The two species used in this study namely: T. harzianum (isolate-27) and T. viride (isolate-08) were kindly provided by Prof. Younes Yousef Molan, Department of Plant Protection King Saud University, Riyadh, Saudi Arabia. These two fungal species were, originally isolated along with other species from soil samples collected from different agricultural fields in Riyadh region, Saudi Arabia, using dilution plate method onto Trichoderma selective media (TSM) according to Elad and Chet (1983). The fungal isolate T. harzianum (isolate-27) and T. viride (isolate-08) were purified through subcultures from single spores and identified to species level based on sequences of the Internal transcribed spacer regions 1 and 2 (ITS1 and ITS2) of the ribosomal DNA ( Maymon et al., 2004 and Hermosa et al., 2000).