Biological Control of Sclerotium rolfsii by Using Indigenous Trichoderma spp. Isolates from Palestine

The bioagent, Trichoderma species are known antagonists of other fungi, and have been shown to be very efficient biocontrol agents of several soil borne plant pathogenic fungi. Forty-seven local Trichoderma isolates were isolated from one hundred sixty nine soil samples from irrigated fields in the West Bank by using dilute plate techniques on Tri- choderma selective media (TSM).The antagonistic potential of the local isolates against the phytopathogenic Sclerotium rolfsii was investigated in dual culture and bioassay on bean plants. Application of testing isolates as a conidial suspension (3*10 6 ) greatly reduced the disease index of bean plants in different rates by a percentage of 67% .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. The results showed that Jn14 and T36 were the most effective isolates at 25 °C and inhibited S. rolfsii mycelial growth at a percent- l age of 79% due to fungitoxic metabolites production. Sporulation of the isolates reached a peak at 30 °C and decreased at 35 °C. The maximum absolute conidia production was 1.5*10 9 conidia / 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 in plant by 133% - 217% respectively. Germination of bean seeds treated with Trichoderma isolates occurred about four days earlier than those in untreated soil.