【作者】 李敏；

【导师】 李元喜； 张帆；

【作者基本信息】 南京农业大学 ， 农业昆虫与害虫防治， 2013， 硕士

【摘要】 烟粉虱(Bemisia tabaci Gennadius)自100多年前被记载以来,已是广泛分布于亚热带和热带地区温室农业系统中的重要害虫之一。生物防治作为最重要防治手段,越来越受到人们的重视。浅黄恩蚜小蜂(Encarsia sophia Girault&Dodd)是烟粉虱的主要寄生性天敌之一。为揭示寄生蜂寄生对其寄主的生理调控机制,室内对浅黄恩蚜小蜂寄生与未被寄生寄主烟粉虱若虫体内三种保护酶活力和三种营养物质含量变化进行了测定,结果如下：(1)根据浅黄恩蚜小蜂对寄主烟粉虱进行寄主检测或者产卵过程中,寄主体表会产生穿刺孔的现象,通过识别穿刺孔来初步判断烟粉虱若虫是否被浅黄恩蚜小蜂寄生。利用该方法,可以较为快捷方便地确定烟粉虱是否被寄生。(2)与对照相比,被浅黄恩蚜小蜂寄生后,3龄和4龄烟粉虱体内POD(Peroxidase)和SOD(Superoxide dismutase)活力的变化明显,均是先升高后降低,然后趋于稳定；CAT(Catalase)活力变化不大。被寄生12小时内,POD活力先升高达到最大值后下降。其中,3龄烟粉虱若虫被寄生3h和9h后的POD活力显著高于对照(P<0.05),分别为未被寄生的2.53倍和1.63倍。4龄寄主被寄生6h和9h后的POD活力显著高于对照,分别为对照组的的2.39倍和1.78倍。3龄寄主被寄生12,24,48,72h后,POD活力跟对照相比没有显著差异。被寄生24h和48h后,4龄寄主POD活力显著低于对照。被寄生24内,SOD活力先升高然后降低至与对照没有显著差异。其中,3龄烟粉虱若虫被寄生3、6、9和12h后,SOD活力均显著高于对照,分别为对照的1.48倍,1.67倍,1.68倍和1.31倍。4龄寄主被寄生6、9和12h后,SOD活力分别为对照的1.50倍,1.49倍和1.60倍。被寄生24、48和72h后,3龄和4龄寄主SOD活力与对照相比均无显著差异。(3)未被寄生的2龄,3龄和4龄烟粉虱三种营养物质相比较,糖原含量3龄最高,蛋白质和脂类含量4龄最高,三种营养物质均是2龄最低,且与另外两个龄期相比均有显著差异。小蜂寄生使烟粉虱体内糖原含量增高,被寄生72h后,3龄和4龄烟粉虱糖原含量分别为12.08μg/头、10.72μg/头,显著高于未被寄生的烟粉虱糖原含量(10.02μg/头、9.39μg/头)。被寄生后,烟粉虱的蛋白和脂类含量有降低的趋势。被寄生72h后,4龄烟粉虱体内蛋白质含量下降了19.54%,与对照相比差异显著,2龄和3龄烟粉虱体内蛋白含量变化不大。被寄生48h后,3龄和4龄烟粉虱若虫脂类含量开始降低,被寄生72后,显著低于未被寄生烟粉虱的含量。2龄烟粉虱若虫被寄生72h后,其体内脂类含量略有降低。结果说明：被浅黄恩蚜小蜂寄生24h内,3龄和4龄烟粉虱若虫保护酶系统中SOD活力和POD活力升高,CAT活力基本上没有变化。推测被浅黄恩蚜小蜂寄生后可引起烟粉虱若虫体内自由基含量升高,寄主需要通过提高SOD和POD的活性来清除这些多余的自由基,从而降低自由基的毒害,浅黄恩蚜小蜂可以短时间内调控寄主体内的生理环境,为其后代的发育提供了一个相对安全的生理环境。浅黄恩蚜小蜂的寄生使寄主烟粉虱体内糖原含量增高,脂类和蛋白质含量降低,说明其寄生可以调控寄主体内的营养物质含量；3龄和4龄寄主体内三种营养物质均显著高于2龄寄主,这有可能是浅黄恩蚜小蜂选择寄生3龄和4龄寄主的原因之一更多还原

【Abstract】 The sweet potato whitefly, Bemisia tabaci (Gennadius) was described over100years ago and has become one of the most important pests in subtropical and tropical agriculture as well as in greenhouse production systems. Biological control could be an attractive alternative management for whiteflies. Encarsia sophia (Girault&Dodd) is one of the most important parasitoid species parasitizing B. tabaci. To explore the mechanism of physiological and biochemical effects of wasp parasitization on its hosts, activities of three Antioxidant-Related Enzymes’ and levels of three nutrition in the nymphs of host Bemisia tabaci parasitized and unparasitized by Encarsia sophia were examined. The main results are as following.(1) According to a pin hole left on B. tabaci after host detection or oviposition by E. sophia, we can determine whether E. sophia really oviposited host through observing the pin hole. We can quickly make sure B. tabaci was parasitized by this method.(2) Changes of POD (Peroxidase) and SOD (Superoxide dismutase) activity showed similar tendencies in two different instars of B. tabaci nymphs after parasitized by En. sophia. It increased to a peak, and then decreased to a stable level. CAT (Catalase) activity in parasitized nymphs changed very few compared with that in control. Within12h, POD activity of parasitized nymphs increased to a peak, and then decreased. POD activity of3rd whitefly nymphs at3h and9h after parasitized were as2.53times and1.63times, respectively, as that in non-parasitized ones. POD activity of4th whitefly nymphs at6h and9h after parasitization were as2.39and1.78times, respectively, as that in non-parasitized ones. POD activities begun to decrease until24h post-parasitization and then kept at a stable level for3rd nymphs parasitized at12,24,48and72h. While the POD activity of the4th instar nymphs parasitized at24h and48h were significantly lower than those in non-parasitized ones. After being parasitized, SOD activity increased to a peak at24h, and then decreased and kept at stable level. SOD activity of3rd whitefly nymphs at3,6,9and 12h after parasitized were as1.48times.1.67times.1.68times and1.31times, respectively, as those of non-parasitized ones. SOD activity of4th whitefly nymphs at6,9and12h after parasitized were as1.50times,1.49times and1.60times, respectively, as that of non-parasitized ones at corresponding times. SOD activities of parasitized3rd and4th instar nymphs at24,48and72h were not significantly different from that in control group.(3) Comparison of nutrition content was carried out among the three instars of B. tabaci nymphs, we find that3rd instar B. tabaci had the highest glycogen content and4th instar had highest lipid and protein content. All these three nutrition contents in2nd instar B. tabaci nymphs were the slightest, which were significantly lower than that in3rd and4th instars. At72h after being parasitized the content of glycogen in3rd and4th instars of B. tabaci were12.08μg/individual,10.72μg/individual, respectively, and were significantly higher than that in unparasitized hosts (10.02μg/individual,9.39μg/individual). The contents of lipid and protein of parasitized B. tabaci were decreased. At72h after being parasitized, the content of protein in4th instar B. tabaci decreased19.54%, and was significantly lower than that in unparasitized ones. The content of protein for2nd and3rd instars was not significantly different between parasitized and unparasitized nymphs of B. tabaci. The content of lipid in3rd and4th instars B. tabaci began to decrease after parasitized for48h. At72h after parasitized, the content of lipid in3rd and4th instar B. tabaci nymphs were significantly lower than that in unparasitized ones. The content of lipid in2nd instar B. tabaci nymphs decreased after parasitized for72h.The results suggest that the POD and SOD activities of3rd and4th instar nymphs increased to a top and then decreased after E. sophia parasitized within24hours, and CAT activity changed little. These results indicated that ROS may be involved in whitefly nymphs’defense responses to E. Sophia infection. The higher POD and SOD activities would help parasitoids degrade excess ROS and maintain the ROS balance. Then the enzymes activities almost decreased to the normal ones. It seems that the physiology environment of the host was suitable for the offspring of the parasitoid.The content of glycogen was higher and the content of lipid and protein were lower in the B. tabaci parasitized by E. sophia. That3rd and4th instars have more abundant nutrition is one of the possible reasons that E. sophia prefers parasitize the3rd and4th instars to2nd ones.更多还原