Screening Of Antagonistic Trichoderma To Sunflower Yellow Wilt And Study On The Biocontrol Mechanisms

Verticillium wilt is a serious vascular diease caused by a soil borne pathogen Verticillium dahliae Kleb. in sunflower. Aiming at production of sunflower still exist the difficulty of the disease control, and little control technology research of sunflower Verticillium wilt at home and abroad. Trichoderma as a universal biocontrol fungus has attracted a lot of attention. In this study, the experiment is focus on screening of Antagonistic Trichoderma to Verticillium dahliae and study on the biocontrol mechanisms. The results showed as follows:1. In this experiment,80 strains of Trichoderma isolated from potato and sunflower stalks and roots collected from different locations which more than 200 samples. Through the plate screening method, the potted experiment and the field text, the results indicate that the strain XM-7 that possed stronger potential ability to biocontrol were selected through the antagonistic tests against Verticillium dahliae. In the field experiment, the strain PT-15 also showed significant control effect achieved 80.28%, which is better than chemicals flusilazole, there were no significant difference with strain XM-7, but this strain performance instability in the potted experiment and confrontation test. The results showed that, in contrast, XM-7 was relatively stable, combined with the potted experiment and the field text, the strain XM-7 possed stronger potential ability to biocontrol.2. By means of molecular biology and morphology methods, isolates XM-7 was identified as Trichoderma citrinoviride.3. Trichoderma citrinoviride XM-7 biological characteristics research results showed that the PDA culture medium was the best medium for the XM-7. The optimum mycelium growth temperature of XM-7 was 30℃, and the optimum spore temperature was 25℃, and pH5-6 was the optimum pH for XM-7 mycelium growth, and pH7 was the most favorable for the conidiation. Soluble starch and mannosc is optimum carbon source for XM-7 mycelial growth, glucose and sucrose is the carbon source for XM-7 sporulation and the optimum nitrogen source was beef extract, illumination has little influence to XM-7 mycelium growth and sporulalion, different trace elements have a certain impact on the mycelial growth and sporulation of the XM-7.4. Preliminary results of biocontrol mechanisms indicated that the hyperparasitism of Verlicillium dahliae by Trichoderma cilrinoviride on sunflower was obvious; XM-7 at the sunflower amount of colonization in rhizosphere soil in 28d after inoculation, achieveed more than 50%; different treatments have some effect on the defense enzymes of sunflower leaves and roots, compared with the control, reatment of biocontrol strains significantly increased the activity of PPO, POD, CAT and SOD activity in sunflower leaves and roots.