An-Najah Staff

The effect of indigenous Trichoderma isolates against the soil-borne phytopathogen Rhizoctonia solani was investigated in dual culture and bioassay on bean plants. Ap- plication of the bioagent isolates as a conidial suspension (3*107) greatly reduced the disease index of bean plants caused by R. solani in different rates and the most effective Trichoderma harzianum isolate (Jn14) reduced the disease by 65%. In dual culture, the T. harzianum (Jn14) overgrew the pathogen R. solani in an average of 16.75 mm/day at 30 °C. In addition, the results showed that T. harzianum (Jn14) and T. hamatum (T36) were the most effective isolates at 25°C and inhibited R. solani mycelial growth by 42% and 78% respectively, due to fungitoxic metabolites production. The Effect of Trichoderma on bean seedlings growth was obvious; height was nearly doubled (160% - 200%), while fresh and dry weights increased by 133% and 217%, respectively. Ger- mination of bean seeds in treated soil with Trichoderma isolates occurred about four days earlier than those in untreated soils. The results revealed however some variation between isolates which was due to genetic variation, mycelium-coiling rate, sporulation rate, fungitoxic metabolites, induced growth response and temperature effect.