| Soybean cyst nematode (SCN), Heterodera glycines, is an obligate endo-parasitic nematode, which is distributed in all the soybean growth areas of the wolrd and is one of the most important plant pathogen in soybean. In this study, the potential biocontrol fungus strains were isolated from cysts, second-stage-juvenile (J2) and eggs of SCN populations from Zhejiang, Shanxi and Anhui, and the rhizosphere soil of soybean. The effects to SCN, biological characters, and application to control SCN of the potential fungus strains were evaulated and characterized. The main results are sommarized as follows:1.145 fungus strains were isolated and screened from cysts, J2 and eggs of SCN, and the rhizosphere soil of soybean.33of which with different colony and morphology were selected for evaluation of biocontrol of SCN. It was found that isolates, HZ-4, HZ-9, HZ-L9, TG-1, TG-15, TG-L37 and AH-8, had effect on the motality of J2; and strains, HZ-L9, HZ-9, HZ-L26, AH-1, AH-L6, TG-L5 and TG-16, could inhibit egg hatching in cysts and females. The fermentation liquor of strain HZ-L9 and HZ-9 had the most efficient inhibition on the egg hatching, inhibition rate at 10 x dilution of the fermentation liquor of the two strains can reach 79.4% and 80.6%, respectively.2. Based on morphological and molecular characters, HZ-L9 and HZ-9were identified as Trichoderma virens and Trichoderma hamatum, respectively. The toxicity tests of strain HZ-L9 and HZ-9 to SCN were tested. Both of the strains had good effects on the motality of J2 of SCN, and lethality rate reached84.2% and 83.3%at the concentration of 108cfu/ml spore suspension,respectively. In addition, It was found that the two strains had good effect on the motality of important nematode speceis in agriculture and forestry, such as Meloidogyne incognita, Ditylehchus destructor, Aphelenchoides besseyi, and Bursaphelenchus xylophilus, for instance, strain HZ-9 at the concentration of 108cfu/ml spore suspension, the lethallty rate was 85.6% for Bursaphelenchus xylophilus, and even reached 58.3% for M. incognita.3.The greenhouse experiments for control SCN with strain HZ-L9 and HZ-9 showed that both strains had good effects on control SCN. The inhibation rate of cysts was increased and nematode infection rate in roots was decreased with increasing the concentration of spores of the two strains. When the concentration of spores of the two strains reached 109cfu/ml, the inhibation rates of cysts were reached 88.3% and 86.4%, and nematode infection rate in roots decreased by 80.8% and 81.3%, respectively. In addition, we also found that both strains can promote the growth of soybean.4. Biological studies indicated that:For strain HZ-L9, the optimum temperature for growth and sporulation were 25℃ to 30℃ and at 30℃, respectively;Light conditions have no significant effect on growth of mycelium, but the highest sporulation was in 24 h illumination; the suitable pH for growing and reproduction is pH 6; Carbon sources have no significant effect on the growth of hyphae, while glucose and fructose benefit sporulation; Ammonium sulfate and beef extract were optimum nitrogen sources for mycelial growth, and yeast extract benefits for sporulation. As to strain HZ-9, the optimum temperature for growing was from 25℃ to 28℃ and for sporulating was at 28℃; The effects of light and pH on strain HZ-9 were similar to that of strain HZ-L9; Soluble starch benefitedfor growth, while galactosum benefitedfor sporulation; Yeast extract was the optimum nitrogen source for growing and reproduction. |
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