商陆根际真菌Aspergillus fumigatus SL-30杀螺有效成分MI的生物安全性

Biological Safety of the Molluscicidal Ingredient from Aspergillus fumigatus SL-30 Isolated from Rhizosphere of Phytolacca acinosa

目的了解商陆(Phytolacca acinosa)根际真菌Aspergillus fumigatus SL-30杀螺有效成分硫代二酮哌嗪类化合物(MI)的生物安全性。方法将MI用去氯水配制成0.01至0.60 mg/L等一系列浓度,采用浸杀法测定MI杀灭钉螺(Oncomelania hupensis)活性,分别于24、48和72h统计各组钉螺死亡率并计算半数致死浓度(LC50);采用半静态法测定0.5～4.0 mg/L等一系列浓度MI对斑马鱼(Brachydanio rerio)、河虾(Macrobrachium nippoensis)和泽蛙(Rana lim-nochris)蝌蚪的急性毒性,于24、48和72 h观察实验动物的反应并统计死亡情况;采用自然土壤法测定1 mg/kg和10 mg/kg MI对蚯蚓(Eisenia fetida)的影响,于第7和14天各观察1次,统计各处理组蚯蚓的死亡和中毒情况;采用密闭碱液直接吸收法测定10 mg/kg MI对土壤微生物的影响,分别于第2、5、7、10、12和15 d测定并计算每100 g干土的CO2释放量。结果24、48和72 h MI杀灭钉螺的LC50分别为0.101、0.062和0.022 mg/L;斑马鱼、河虾和泽蛙蝌蚪的死亡率均随药物浓度升高而增高,各实验动物24、48和72 h的LC50值分别为1.941、1.755和1.219 mg/L(斑马鱼),3.170、2.720和2.419 mg/L(河虾),2.109、1.751和1.288 mg/L(泽蛙蝌蚪)。MI对蚯蚓的LC50>10.0 mg/kg。MI为10 mg/kg时,15 d内对微生物呼吸的抑制率均低于50%。结论 MI对斑马鱼、河虾和泽蛙蝌蚪的毒性远低于对钉螺的毒性,在有效杀螺浓度范围内,MI对供试水生非靶生物是安全的;MI对蚯蚓和土壤微生物属低毒级。

Objective To study biological safety of the molluscicidal ingredient （MI, a kind of diketopiperazines） in the exocellular broth of Aspergillus fumigatus SL-30＇ which was isolated from the rhizosphere of Phytolacca acinosa. Methods The MI was prepared in concentrations ranging from 0.01 to 0.60 mg/L, at the same time molluscicidal activity against Oncomelannia hupensis was tested by using immersion method, and the LCso in the case of immersion time for 24, 48 and 72 h was calculated. Acute toxicity of the MI with concentration ranging from 0.5 to 4.0 mg/L on Brachydanio rerio, Macrobrachium nippoensis and Rana limnochris was performed by standard laboratory procedure, and mortality rate of the tested animals with treated time of 24, 48 and 72 h was recorded. Effect of the MI on Eisenia fetida was tested using natural soil procedure with the dose of 1 and 10 mg/kg, and the poisoning performance and mortality in the 7th day and 14th day were recorded. Inhibition of the MI at 10 mg/kg on respiration of soil microorganisms was determined by sealed alkaline direct absorption method, and the released amount of CO2 （mg/100 g） in the 2nd, 5th, 7th, 10th, 12th and 15th day was determined. Results Molluscicidal activity of the MI against Oncomelania hupensis was shown with LCso 0.101, 0.062, and 0.022 mg/L in 24, 48 and 72 h, respectively. Mortality rate of Brachydanio rerio, Macrobrachium nippoensis and Rana limnochris all increased with the increase of MI concentration, and the LCso of each kind of tested animals was recorded as follows： 1.941, 1.755 and 1.219 mg/L for Brachydanio rerio, 3.170, 2.720 and 2.419 mg/L for Macrobrochium nippoensis, 2.109, 1.751 and 1288mg/L for Rana limnochris in 24, 48 and 72 h, respectively. The LCsoof MI on Eisenia fetida was 〉10.0 mg/kg. The inhibition rate of MI was less than 50% with a concentration of 10 mg/kg in 15 days. Conclusion The MI shows molluscicidal activity on Oncomelania hupensis with much lower toxicity on Brachydanio rerio,Macrobrachium nippoensis and Rana limnochrisn. The MI is safe to non-target aquatic organisms, and to both Eisenia fetida and soil microorganisms under the effective mollussicidal concentration.