【作者】 田丽；

【导师】 冯明光；

【作者基本信息】 浙江大学 ， 微生物学， 2005， 博士

【摘要】 球孢白僵菌.Beauveria bassiana是一种经典的害虫生防真菌,在国内外农林害虫防治中发挥着重要作用。本研究采用符合规范的生物测定方法,系统评价了球孢白僵菌SG8702菌株纯孢粉与亚致死剂量杀虫安混用对小菜蛾的协同增效作用,并就孢子可湿性粉剂的配方筛选及贮存进行了试验,以期为适用新型生防真菌制剂的研制提供依据。 球孢白僵菌与杀虫安对小菜蛾幼虫互作效应评价 按国际规范标准采用喷塔喷雾接种法,对未剂型化孢子粉的水悬液进行了与亚致死浓度的杀虫安（O、5、10、25、50和100 μg/mL）混用对小菜蛾二龄幼虫协同互作的6次生物测定试验,每次试验中接种的孢子剂量一律规范为单位面积孢子附着量（孢子数/mm²）,含高、中、低3个孢子浓度处理,并设相应的无菌对照,每个浓度处理包括3个重复共96～116头幼虫。所获生测数据经时间—剂量—死亡率模拟分析,SG8702菌株对小菜蛾幼虫的毒力很高,接种后LC50从第4天的269个孢子/mm²降低到第8天的107个孢子/mm²当与相容性良好的化学杀虫剂杀虫安以5～100μg/mL的亚致死剂量互作时,白僵菌对小菜蛾的LC₅0降低和LT₅0缩短。菌液中加入25μg/mL的杀虫安,接种后第6天起LC₅0被降低4～5倍;加入50μg/mL,,接种后第4天起LC₅0被降低12～42倍:加入100μg/mL,接种后第3天起LC₅0被降低9～2458倍,显示25～100 μg/mL的杀虫安亚致死剂量能显著增强或加快球孢白僵菌对小菜蛾的作用效果。 孢子可湿性粉剂的配方筛选通过14种润湿剂对SG8702菌株孢子粉的湿润力和生物学相容性的测定和比较,SDS（十二烷基苯磺酸钠）的湿润力最强,但显著抑制孢子萌发;有机硅表面活性剂曾被推荐用于生物真菌制剂中,但供试的11种有机硅表面活性剂对白僵菌孢子的润湿效果并不理想。综合润湿效果与孢子相容性,NP-10可作为孢子可湿剂的润湿剂,添加比例为3%,在此配比下菌剂的润湿时间仅为5.2秒,远低于国家对可湿性粉剂润湿时间小于180秒的标准,而且对孢子活力无显著影响。测定的9种分散剂对孢子萌发率均表现负面影响,其程度因浓度而异。与对照相比,除NPJ在1%和3%浓度下无显著影响外,其余分散剂在1～5%的组合中均显著降低孢子萌发率。供试9种分散剂在不同浓度下对孢子悬浮稳定性的影响差异并不显著,但悬浮稳定性普遍高于不加分散剂的孢子悬浮液。从分散性和生物相容性两方面考虑,NPJ可作为白僵菌孢子可湿剂的分散剂,适宜配比为1%。此外,在两种紫外保护剂的比较试验中,抗坏血酸作为紫外保护剂优于荧光素钠,配比为O.5%左右。更多还原

【Abstract】 As a classic fungal biocontrol agent, the entomopathogenic fungus Beauveria bassiana has played an important role in control of insect pests infesting crops or forests worldwide. The present study sought to evaluate quantitatively interactions of B. bassiana SG8702 with sublethal application rates of profurite aminium, a chemical insecticide against lepidopteran pests in China, by means of a standard bioassay protocol and to optimize components as additives to a wettable B. bassiana formulation for better application and storage in ambient environment.Time and concentration dependent interactions of B. bassiana and profurite aminium. Six bioassays were conducted to evaluate interaction between B. bassiana SG8702 and profurite aminium, a chemical insecticide highly compatible with the fungal biocontrol agent, against diamondback moth Plutella xylostella. Second instar larvae were exposed to sprays of B. bassiana alone (assay 1) at the concentrations of 21-38, 157-232 and 822-1133 conidia/mm2 or together with the chemcial at the low application rates of 5, 10, 25, 50 and 100 a.i. ug/ml (assays 2-6). and then maintained at 25°C and 12:12 h light:dark photoperiod for daily monitoring mortalities for 8 days. Based on modeling the resultant time-concentration-mortality data sets, the fungal agent was highly virulent to P. xylostell with an LC50 decreasing from 269 conidia / mm2 on day 4 to 107 on day 8. Lower lethal concentrations or shorter median lethal times resulted from fungal sprays including the tested chemical rates, which never caused higher mortalities than the fungal treatments alone. The fungal action was significantly enhanced by inclusion of the chemical 25 μg/ml in the fungal sprays for 4-5 fold reduction of the LC50 from day 6 after spray, 50 ug/ml for 12-42 fold reduction from day 4 after spray, 100 μg/ml for 9-2548 fold reduction from day 3 after spray, respectively. These rates were equivalent to 5-20% of the chemical rate labeled for fieldapplication. The fungal and chemical interaction clarified above highlights the feasibility of combined formulation or application of B. bassiana and the chemical insecticide for P. xylostella control.Optimized components as additives to wettable formulation. Based on measuring wetting times of 14 wetting agents and assaying their compatibilities to B. bassiana conidia, dodecyl sodium sulfate was found wetting the conidia most rapidly but significantly impairing conidial viabilities. Since organic silicon compounds have been recommended in previous reports, 11 surfactants of such compounds were included in the study but none of them was found being desirable for wetting the conidia. Based on wetting efficiency and compatibility, the surfactant NP-10 was a satisfactory wetting agent for B. bassiana conidia because it took only 5.2 sec to well wet conidia when incorporated into the formulation at 3% and had insignificant influence on the conidial viability. The negative effects of 9 dispersants on conidial germination increased with their proportions in most of the cases although all enhanced the stability of conidial suspension. In comparison to a blank control, the dispersant NPJ was exceptional and had no significant impact on conidial germination at the application rates of 1-3%. Thus, this dispersant was chosen for use in the wettable formulation at a desirable proportion of 1 %. In a comparative assay of two UV protentants, ascorbic acid (vitamin C) at 0.5% protected B. bassiana conidia better from damage by UV radiation than sodium carboxymethyl cellulose.Storage and shelf-life of wettable formulation. For the wettable formulation of B. bassiana conidia including 3% NP-10 as wetting agent, 1% NPJ as dispersant and 0.5% ascorbic acid as UV protectant, a 6-month storage at 25°C in dark resulted in a conidial viability of 80%, which was much higher than the viability of 55% observed from the unformulated conidia stored at the same regime. At the time of 12 months after storage, the formulated and unformulated conidial had viabilities of -60 and 8.7%, respectivelyo This indicates that B. bassiand. conidia in the wettable formulation were more tolearable to ambient storage than those unformulated. Moreover, it was confirmed that a residue rice powder (ground from rice grains from which conidia were grown and harvested) could be used for improving ambient storage of the wettable formulation by partially replacing diatomite as carrier. During an 18-month storage of wettable formulations containing thesame additives but different proportions (0, 20, 40, 60, 80 and 100%) of the rice powder, a carrier consisting of 40% rice powder and 60% diatomite was found favoring protection of conidial viability in the formulation. When B. bassiana was formulated in conjunction with 2.5, 5 and 10% of profurite aminium, however, the conidial viabilities in the combined formulations stored at either 4 or 25°C were greatly affected during a 6-month period of storage. At the time of 3 months after storage at 4°C, incorporation of 2.5, 5 and 10% of the chemical into the formulation resulted in viabilities of 89.7, 82.4 and 80.3% (95.2% in CK); such viabilities dropped to 35, 30.2 and 19.3%( 94% in CK) by the end of the storage. The much worse storage occurred at 25°C with the viabilities leaving 43.6, 19.6 and 14.3% (92.3% in CK) 3 months after storage but becoming undetectable at the end of the following month. Due to the undesired long-term compatibility with B. bassiana, the chemical insecticide could not be formulated together with fungal biocontrol agent although their positive interactions on P. xylostell may support in situ combination for field application.更多还原