| Trichoderma species is the important biocontrol microorganism, which has potential to control plant diseases. Many strains Strains of Trichoderma were isolated aiming at the control of soil-borne diseases of peanut, eggplant, capsicum and herbal medicine plants. Trichoderma harzianum T23, which has important potential to control plant diseases, was obtained and its biological characters and control effect were studied, and the antagonistic mechanism employed by T23 was also preliminarily observed in this paper.1. Isolation and selection of Trichoderma strains. 176 Trichoderma strains were isolated through dilution-plating method or pathogen induced method from 151 rhizospheric soil samples collected from varied entironraents. Trichoderma harzianum T23, which has important potential to control plant diseases, was obtained through lab bioassay and field potted plant testing. It was characteristic of wide antagonistic spectrum, high antagonistic efficacy, fast hyphae development and large conidia yield.2. Biological characters of Trichoderma harzianum T23. The impacts of media composition, temperature, PH value, humidity and illumination hour on the spore yield and hyphae development of T23 were tested. The results showed that significant increases in both the development of hyphae and spore yield were achieved on PDA with 12-hour illumination plus 12-hour dark at 25℃~ 30℃ when the PH value is 5~7, and the relative humidity is 90%~100%. On those conditions, the colony diameter was 8. 9cm on 3rd day, and the spore yield was 3.9×10~9 spores/ml on 5th day.3. Control effects of Trichoderma harzianum T23 preparation in field trails. Small plot trials were conducted to reveal the biocontrol of T23 preparation. The results showed that the control effects of T23 preparation against Scelerotium rolfsii of peanut, root rot of Ophiopgon japonicus, root rot of Ligusticum chuanxiong, Verticiilium wilt of eggplant and Scelerotium rolfsii of pepper were 58.83%, 55.61%, 63.90%, 67. 85% and 64. 91%. respectively.The yield of peanut, eggplant, Ophiopgon japonicus and Rhizoma chuanxiong wre increased by 18.58%, 52.98%, 25.69% and 17.45%, respectively.Field demonstrations in lOOhnf of peanut, lOOhm" of Ophiopgon japonicus and lOhm" of Ligusticum chuanxiong treated with T23 preparation showed that the control effects of T23 preparation against Scelerotium rolfsii of peanut, root rot of Ophiopgon japonicus and root rot of Ligusticum chuanxiong were 67.23%, 61.20% and 67.54%, respectively. The yield of peanut, Ophiopgon japonicus and Ligusticum chuanxiong were increased by 15. 00%, 16. 10% and 9. 26%, respectively.4. Antagonistic mechanism of Trichoderma harzianum T23. Antibiosis, mycoparasitism, competition and lysis of pathogen hyphae are the main mechanisms employed by T23. But the mechanisms are varied in the control of different pathogens. It was proved that antibiosis, competition for nutrition and space were the main mechanisms in the control of Fusarium oxysporum, antibiosis and mycoparasitism were the main mechanisms in the control of Scelerotium rolfsii, and mycoparasitism and lysis of pathogen hyphae were the main mechanisms in the control of Rhizoctonia solani. The phenomena that T23 hyphae' s coiling around pathogen hyphae, penetration and subsequent dissolution of the host cytoplasm were also observed.The chitinase in liquid media of T23 was tested. It was illustrated that chitinase activity of T23 is positively correlated with culture time within 7 days, it was 2. 35U on 3rd day, and reached 65. 72U on 7th day. The significant increase in chitinase activity occurred in 4d~5d. |
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