蜡蚧轮枝菌致病性初步研究

通过对蜡蚧轮枝菌V-816菌株致病性的研究,结果表明,该菌对菜青虫、小菜蛾、甘蓝蚜、棉叶螨有较强的致病力.随浓度增加,杀虫效果明显提高,且对幼龄幼虫的致病力较对老龄幼虫的强.温度对该菌的致病力有明显的影响,其致病适温为25～30℃.同时试验表明该菌不侵染七星瓢虫的幼虫.     

蜡蚧轮枝菌对扶桑绵粉蚧的致病性研究

测定了蜡蚧轮枝菌Verticillium lecanii MZ041024菌株对扶桑绵粉蚧Phenacoccus solenopsis Tinsley的致病性。结果表明蜡蚧轮枝菌MZ041024菌株对扶桑绵粉蚧1龄若虫的致病率为83.72%,致死中浓度LC_(50)为1.49×105个/m L,致死中时间LT50是5.21 d;对2龄若虫的致病率为74.42%,致死中浓度LC_(50)为3.66×10~3个/m L,致死中时间LT50是5.55 d;对3龄若虫的致病率为76.74%,致死中浓度LC_(50)为9.82×104个/m L,致死中时间LT_(50)是5.44d;其对雌成虫的致病率为85.37%,致死中浓度LC_(50)为2.80×10~4个/m L,致死中时间LT_(50)是4.87 d。说明蜡蚧轮枝菌MZ041024菌株对扶桑绵粉蚧有较强的致病性。     

菜青虫感染蜡蚧轮枝菌后的组织病理变化

对感病菜青虫Pieris rapae组织切片的观察研究表明, 蜡蚧轮枝菌Verticillium lecanii主要通过昆虫的体壁侵染虫体。菜青虫各龄幼虫在体壁接菌12 h后,附着在虫体表面的孢子即可萌发。2～3龄幼虫,蜡蚧轮枝菌菌丝24 h就可穿透体壁进入血腔,48 h可见脂肪体等器官发生病变; 4～5龄幼虫,36 h菌丝才可穿透体壁,48 h可见虫体内有部分菌丝体。侵入虫体内的菌丝对寄生组织没有选择性。菌丝首先在入侵的血腔中生长,然后侵入脂肪体和肌肉,随菌丝在虫体内的增殖,中肠、马氏管、丝腺等相继被侵染。受侵的组织器管均发生明显的病变,如体壁分离,脂肪体变形、溶解,肌纤维排列松散,中肠上皮细胞脱落并出现许多空泡等。     

影响蜡蚧轮枝菌发酵产孢量和孢子活力的基本因素分析

不同接种浓度、发酵时间、菌株和基质对蜡蚧轮枝菌固体发酵的产孢量都有显著影响,而对孢子活力的影响不明显,萌发率均在90%以上.在5至7天内,随发酵时间的延长产孢量有明显增长;7至10天则变化不大;15天时产孢量和孢子活力均显著降低.随接种孢子浓度每增加1倍,菌株(VLFNL95-01)发酵的产孢量平均提高15.6%,浓度加大至32倍则提高71.9%.3个菌株比较,VLFNL95-01产孢量明显高得多.不同固体基质发酵的结果有显著差异,产孢量最高的(正交3号配方)比其次的(黄豆饼粉+玉米碎粒+磷酸盐)就提高了95.1%.     

蜡蚧轮枝菌固体发酵基质的筛选与组分优化研究

对昆虫病原真菌一蜡蚧轮枝菌菌株Tri—BA81进行5种单一基质和4种合基质固体发酵,初筛出谷子单一基质和谷子＋麦麸＋磷酸盐组合基质为最佳发酵基质,后者的产孢量是前者的3倍多。选取谷子、麦麸、磷酸盐和稻壳为4个组分因子,每个因子分别设有不同质量比例的3个水平,按正交设计（L94^3）进行优化组合筛选研究。结果表明,产孢量最高的正交组合为5号配方,分生孢子产量达1．68×10^10个／g。     

蜡蚧轮枝菌和球孢白僵菌的共发酵

【目的】球孢白僵菌(Beauveria bassiana)和蜡蚧轮枝菌(Verticillium lecanii)是国内外目前研究应用最广泛的杀虫生防真菌,欲扩大其防治范围、增强防治效果、降低生防成本。【方法】采用共发酵技术,通过组合菌株产孢能力和杀虫毒力比较试验,确定蜡蚧轮枝菌和球孢白僵菌共发酵的可行性。【结果】蜡蚧轮枝菌L-31和球孢白僵菌Q-55共发酵的最佳配比为1:1时,按10%总量接种于发酵培养液中(培养液按酵母膏5.0 g/L、葡萄糖20.0 g/L、麦芽糖提取物5.0 g/L、KH2PO43.0 g/L、黄小米200.0 g/L,pH 6.5配制),23.0°C±0.1°C恒温静置发酵12 d,共发酵液的含孢量可达1×109CFU/mL以上,杀虫毒力比较强,其对温室白粉虱和菜青虫可同时显效,处理9 d后的致死中浓度LC50分别为2.09×104±0.12 CFU/mL和3.17×105±0.11 CFU/mL,发酵液浓度为1×108CFU/mL时的致死中时间LT50分别为2.11±0.14 d和4.27±0.43 d,温室小区试验校正防效在80%以上,与其各单一菌株发酵液的防效之间存在显著性差异。【结论】通过两株生防真菌的共发酵研究,为杀虫真菌的扩谱增效以及植物害虫的有效防治提供科学依据和有效途径。     

四株蜡蚧轮枝菌对桃蚜的侵染力及对其生殖力的影响

通过研究来自不同寄主的 4株蜡蚧轮枝菌菌株对桃蚜的侵染致死力、发病强度指数、以及对无翅成蚜生殖力及子代的影响 ,综合探讨病菌的侵染致病力及其潜力。试验 (2 4℃ ,10 0 % RH,5× 10 6孢子 /ml)结果表明 ,蜡蚧轮枝菌对无翅成蚜的侵染致死力和发病指数总体上是一致的 ,但二者在 4菌株间有明显差异 ,强弱依次为 VL FNL 95≥ VLNTV94 >VL ASA87>VLKTV79;对不同虫态 ,二者也有较大差异 ,对无翅成蚜明显高于有翅若蚜和 2～ 3龄若蚜。上述 4菌株对无翅成蚜的感染死亡高峰 ,依次为 4～ 5天、4～ 7天、4～ 8天和 5～ 9天 ,感染死亡分别为 84 .2 1～ 10 0 %、75.0 0～ 10 0 %、4 8.2 8～ 10 0 %和 2 9.6 3～ 77.78%。其中对 2～ 3龄若蚜 ,菌株间差异不很大。前 2个菌株 6天可达最高发病指数 ,虫体表面布满菌丝和分生孢子。与对照相比 ,可明显抑制无翅成蚜的生殖力。处理后 3天 ,产仔蚜量明显减少 ;4～ 5天锐减 ;8天种群产仔蚜量降低 39.59～ 4 8.37%。     

蜡蚧轮枝菌及其在有害生物防治中的应用研究进展

本文介绍了蜡蚧轮枝菌Lecanicillium spp.的致病性、致病机理、与其他农药的相容性及菌株基因工程改良等内容。蜡蚧轮枝菌的寄主范围极其广泛,寄主至少包括43种昆虫、3种螨类、2种线虫和5种植物病原真菌。蜡蚧轮枝菌一般通过穿透寄主体壁侵入寄主,但长孢蜡蚧菌L. longisporum通过体表寄生豌豆蚜Acyrthosiphon pisum和柑橘粉蚧Planococcus citri而致其死亡;蜡蚧轮枝菌分泌的降解酶和毒素也具有很大的开发潜力;在田间先后施用蜡蚧轮枝菌制剂和农药以及充分利用蜡蚧轮枝菌对植物的内寄生作用可能为蜡蚧轮枝菌与农药的协调应用提供新的思路;原生质体融合、诱变以及转基因是菌株基因工程改良的主要手段;最后,指出了蜡蚧轮枝菌开发过程中存在的问题以及未来的发展方向。     

蜡蚧轮枝菌VL17中杀虫成分分离及鉴定北大核心CSCD

蜡蚧轮枝菌（Verticilliumlecanii）VL17菌株是从罹病的蚜虫中分离得到的一种具有高效杀虫活性的内生真菌。根据生物活性跟踪测试,采用不同溶媒萃取法、硅胶柱分离法、高速逆流色谱法、半制备高效液相分离纯化法,从该菌株的代谢产物中筛选出具有杀蚜虫的有效成分。实验结果表明：经察氏液体培养基培养采用乙酸乙酯提取获得粗毒素对萝卜蚜若蚜的毒杀活性最好;该提取物经HSCCC、HPLC分离纯化后收集到4个馏分,其中馏分Ⅲ对萝卜蚜的防治效果最佳,LC50值为0．4748mg／mL;馏分Ⅲ通过IR、MS初步鉴定推测结果为羧酸酯类化合物,分子量约为437。     

蜡蚧轮枝菌毒素对温室中烟粉虱种群控制作用的评价

在室内测定蜡蚧轮枝菌毒素对烟粉虱种群干扰作用基础上,通过分别组建蜡蚧轮枝菌毒素和化学杀虫剂作用下的烟粉虱第5、6代自然种群生命表,采用种群趋势指数（I）和干扰作用控制指数（IIPC）分析法,比较蜡蚧轮枝菌毒素和化学杀虫剂对茄子上烟粉虱的防治效果,评价蜡蚧轮枝菌毒素对烟粉虱的防治作用。结果表明,毒素对烟粉虱室内种群的干扰作用主要表现在对成虫的忌避作用和对若虫的毒杀作用;温室大棚中施用400mg／L的蜡蚧轮枝菌毒素,对烟粉虱第5代和第6代的控制指数IIPC分别为0．064和0．023,连续施用毒素后,第6代种群趋势指数Ⅰ为0．68,烟粉虱种群基本得到控制;温室大棚中施用重量10％吡虫啉可湿性粉剂（稀释1000倍）,对烟粉虱第5代和第6代的控制指数IIPC分别为0．44和1．01,化防区第5代的I为12．95,第6代的I为30．23,分别为对照区的0．44倍和1．01倍,连续使用化学杀虫剂,容易造成烟粉虱再猖獗。重要因子分析揭示毒索比化学杀虫剂更利于温室烟粉虱种群控制。     

Germination of the entomopathogenic fungus Verticillium lecanii on scales of the glasshouse whitefly Trialeurodes vaporariorum

In a series of laboratory experiments, tobacco leaf discs infested with scales of the glasshouse whitefly Trialeurodes vaporariorum, were immersed in suspensions of conidia of three strains of the entomopathogenic fungus Verticillium lecanii. The germination of conidia on the insect was recorded and compared with the germination of conidia applied to Czapek—Dox Complete Medium. Laboratory bioassays were performed to record the mortality of whitefly scales exposed to conidia of all three fungal strains. The rate of germination of conidia on the whitefly scales was much reduced compared to that oh complete medium. Differences were recorded in the rate of germination of the three strains on complete medium, but not on the whitefly scales. There was no correlation between the pathogenicity of the strains to whitefly scales in laboratory bioassays and the rate of germination on the host.     

Effect of Verticillium lecanii on biological characteristics and life table of Serangium japonicum (Coleoptera: Coccinellidae), a predator of whiteflies under laboratory conditions

Effects of entomopathogenic fungus Verticillium lecanii on biological characteristics and life table of Serangium japonicum , a predator of whiteflies against five different conidial concentrations (1×10⁴, 1×10⁵, 1×10⁶, 1×10⁷, and 1×10⁸ conidia/mL) were studied under laboratory conditions. The developmental periods for all immature stages (from eggs, 1st, 2nd, 3rd, 4th instar nymph and pupae up to emergence) among the treatments were significantly different when compared to that of control, and the longest development period was observed as treated with 1×10⁸ spore/mL. However, no significant difference on the percent survival of all immature stages was observed among the treatments and control. Also, there were no significantly different effects of V. lecanii on mean generation time, intrinsic rate, the finite rate of increase and longevity of S. japonicum among the treatments and control.     

大丽轮枝菌微菌核的萌发条件及致死温度

微菌核是大丽轮枝菌在土壤中的主要存活结构和初侵染源,在土壤中可存活14年之久,其数量及存活状况直接影响着大丽轮枝菌型黄萎病的发生为害程度。以棉花黄萎病菌Verticillium dahliae XJ2008菌株为试材,研究了微菌核萌发的最佳条件、致死温度及土壤温度对微菌核存活的影响。结果表明,20℃、pH8.0是微菌核萌发的最佳条件。大丽轮枝菌微菌核具有很强的耐高温特性,随着处理时间的延长,微菌核的萌发率呈下降趋势,在55℃及以上处理时其萌发率下降迅速,而在50℃及以下处理时其萌发率下降相对较慢,在55℃处理360min可使微菌核完全致死,而在40℃、45℃和50℃处理1,440min,仍然有少量的微菌核存活,但其萌发率随着时间的推移呈下降趋势。土壤微菌核模拟试验结果表明,土壤温度对微菌核有很强的致死作用,40℃条件下处理4d后土壤中的微菌核已全部死亡。该研究结果为通过覆膜增温防治作物黄萎病提供了理论依据。     

The potential of some adjuvants in promoting infection with Verticillium lecanii: laboratory bioassays with Myzus persicae

The potential of 14 adjuvants, including mineral oils, vegetable oils, stickers, spreaders, surfactants and nutrients, in promoting the virulence of the entomopathogenic fungus Verticillium lecanii were compared relative to a commercial formulation of the pathogen. The rate of infection over time with each adjuvant relative to the commercial formulation was tested using the peach potato aphid Myzus persicae. The proportion of infected aphids was modelled binomially with a logistic rate function assumed for the proportion infected over the time period of the experiment. Four of the adjuvant treatments, Codacide, skimmed milk, glycerol and Cutinol together with the commercial control had similar logistic slope parameters and were modelled using parallel regressions. The parallel regressions model showed significant differences between the intercepts with both glycerol and Cutinol significantly better than V. lecanii alone. Glycerol had a more positive intercept than Cutinol but the difference was not statistically significant. Although highly variable, the numbers of progeny produced by the treated aphids were significantly reduced by all the treatments relative to untreated control aphids. Glycerol and Cutinol were the only treatments that significantly reduced the number of progeny relative to the V. lecanii control.     

Time-dose-mortality modelling and virulence indices for six strains of Verticillium lecanii against sweetpotato whitefly, Bemisia tabaci (Gennadius)

Bioassays of six strains of Verticillium lecanii (Zimmermann) Viégas were conducted with the sweet potato whitefly, Bemisia tabaci. For inoculation, batches of third‐instar whitefly nymphs on sweetpotato seedlings were immersed in conidial suspensions of five dosages at concentrations from 10³ to 10⁷ conidia/ml. Each dosage was used to inoculate 150–250 nymphs. The nymphs were maintained at 25°C, under 95% RH, photo phase of 16 : 8 (L : D) and observed daily for mortality. The resulting data were analysed over 8 days by a complementary log‐log (CLL) time‐dose‐mortality model, based on the Hosmer–Lemeshow test, analysing the time‐dose trends for five concentrations of six strains of V. lecanii simultaneously. The parameters from the model were used to estimate the virulence indices (the values of LC₅₀) of six strains against B. tabaci. Based on the time‐dose‐mortality relationships fitted and the virulence indices, the virulence of the six strains of V. lecanii for B. tabai was compared. Results indicated that the strain Vl6063 imported from Canada and the domestic strains V3450 and Vp28 derived from B. tabaci and a scale insect, respectively, were more virulent than the others with LC₅₀ values of 2.57 × 10⁵, 6.03 × 10⁵ and 6.03 × 10⁵, respectively.