An-Najah Staff

The bioagent, Trichoderma species are known antagonists of other fungi, and have been shown to be very potent biocontrol agents of several soil borne plant pathogenic fungi under both greenhouse and field conditions. One hundred sixty nine soil samples from irrigated fields in the West Bank were collected for the recovering of Trichoderma fungal species using Trichoderma selective media (TSM). Forty-seven local Trichoderma isolates were isolated. The antagonistic potential of the local isolates against the phytopathogenic Rhizoctonia solani and Sclerotium rolfsii was investigated in dual culture and bioassay on bean plants. Application of testing isolates as a conidial suspension (3*106) greatly reduced the disease index of bean plants caused by Rhizoctonia solani and Sclerotium rolfsii in different rates by a percentage of 65% and 67%, respectively. The results revealed that the variation of antagonistic potential between isolates was due to the variation in mycelium-coiling rate, sporulation, fungitoxic metabolites, induced growth response and temperature effect. In dual culture, most effective isolate (Jn14) overgrew the pathogens R. solani and S. rolfsii at 30 and 25 oC respectively. In addition, results showed that Jn14 and T36 were the most effective isolates at 25 °C and inhibited R. solani and S. rolfsii mycelial growth at a percentage of 79% and 94.7% respectively due to fungitoxic metabolites production. Sporulation of the isolates reached a peak at 30 °C and decreased at 35 °C. The maximum absolute spore production were 1.5*109 spore / ml by the isolate Jn14 at 30 °C. The Effect of Trichoderma on bean seedlings growth was obvious; height was nearly doubled (160% - 200%), while fresh and dry weight were increased by 133% - 217% respectively. in plant. Germination of bean seeds treated with Trichoderma isolates occurred about four days earlier than those in untreated soil.