Studies On Biocontrol Mechanism Of Trichoderma Species On Trees Diseases

The experiment was carried out with Trichoderma harizanum agent T88. The antifungul activitys of its metabolite ,mycoparasitis activities, the lytic enzymes during the mycoparasitism and induction of defense response in Poplar were studied by dual culture, electronic microscopy and enzyme assay in order to account for the biocontrol mechanisms of T88 on tree diseases. It was important and actual to applied T88 to biocontrol on tree disease. The main results were as follows:1. The volatile and non-volatile antibiotics were produced by Trichoderma harizanum (T88). The volatile antibiotic inhibited the growth of tested pathogens in varying degrees. The inhabition rate of pathogen C.chrysosperma reached 23.61% in 24 hours. The longer culture was, the stronger the inhabition was. The non-volatile antibiotic also inhabited the dry weight of mycelium of pathogens, when the culture contained 50% or 100% filtrates of T88. The dry weight of mycelium of C.chrysosperma reduced individually 49.33%, 96.38% in the autoclaved culture and 59.28%, 96.6l%in the dried autoclaved culture.2. Trichoderma harziamm agent T88 exhibited different modes in the process of myccoparasism on different plant pathogenic fungi. T88 appeared to inhibit pathogen by mycoparasism with evidence of either by coiling around hyphal of R or by forming hooks.and by parallel and waved growth or by penetrating hyphal cells of C.chrysosperma. T88 in dual culture with Dothiorella gregaria leaded to hyphal cells of concentration and disruption.3. Trichoderma harziaman T88 which was grown in the medium contained the chitin and Fulin powder produced chintinase and B-l,3-glucanase to degrade the chitin and B-l,3-gIucose. The decoloured area appeared in the centre of medium . chitinease activities and B-l,3-glucanase activities in the interaction zone were higher than that in single cultures, the chitinase activities was 76.92U/mgPro and the B-l,3-glucanase activities was 18.20 U/mgPro .4. Trichoderma harzianum T88 produced enzymes when it was grown with all of the carbon sources examined. The level of production of enzymes varied depending on the carbon source. The chitinase activities and B-l,3-glucanase activities were the highest in the culture contained the cell-wall of R. the chitinase activities and 6-1,3-glucanase activities were 43.55 U/mgPro, 24.52 U/mgPro. No enzyme activities was detected in the culture contained 2% glucose..5. The effect of culture time on enzyme production of T88 was studied. The chitinase activities and B-1,3-glucanase activities were increased by induction of cell-wall of R and these enzymes activities were the highest in second day after inoculation. And then the enzyme activities were decreased gradually.6. The culture filtrates of Trichoderma harzianum T88 were precipitated with ammonium sulfate (90% saturation). The crude enzyme showed inhibition against the growth of mycelium of R and C.chrysosperma, and appeared the inhibition zone around the hole. Moreover, the inhibition of 200ul crude enzyme was stronger than that of lOOul.7. The branches of Poplar were cultured in the sterile water and inoculated with T88 , and T88 stimulated the plant defense system. The enzyme activities associated with defense response were increased , including POD, PAL, chitinase and 6-1,3-glucanase .