海氏桨角蚜小蜂对两种生物型烟粉虱的功能反应研究

本文报道海氏桨角蚜小蜂Eretmocerus hayati在室内对不同寄主密度下的B型和Q型烟粉虱Bemisia tabaci寄生和取食情况,并比较了该蜂对两种生物型烟粉虱功能反应的差异。结果表明,海氏桨角蚜小蜂对两种生物型烟粉虱的寄生率和致死率可分别达到60%和70%以上,平均每日最大致死量可达40头烟粉虱若虫。该蜂对两种生物型烟粉虱的功能反应曲线符合HollingII型,随寄主密度的增加对烟粉虱若虫的寄生和致死数量均增加直至达到每日最大致死数量,而寄生率和致死率则随寄主密度的增加而显著下降。该蜂对两种生物型烟粉虱的功能反应没有显著的差异。     

Relative abundance of Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) and its parasitoids,and the impact of augmentative release of Eretmocerus spp. (Hymenoptera: Aphelinidae) on the population dynamics of the pest in Burkina Faso (West Africa)

Whitefly infestations and parasitism were monitored year-round in overlapping cotton crops sown on three dates in Burkina Faso. The relative abundance of B. tabaci (Gennadius) and its parasitoids, Eretmocerus spp. and Encarsia spp., was recorded in control and insecticide-sprayed plots. Low B. tabaci populations developed during the first half of the rainy season. Pest populations increased when rainfall was ending, and the levels reached were higher in insecticide-treated plots (48 nymphs/leaf) than in control plots (25 nymphs/leaf). Parasitism reached 88.7% in control plots, and 53.7% in insecticide-treated plots. Eretmocerus spp. nymphs were more abundant than Encarsia spp. in both treated and control plots. A positive and significant curvilinear relationship was observed where % parasitism, on a linear scale, rose to a plateau with logarithmic increase in host density. In general % parasitism was correlated with the abundance of pest populations except in March and April where parasitism increased while B. tabaci populations decreased. In a separate experiment, adult Eretmocerus spp. were released into caged cotton plants to study the impact of augmentative releases of the parasites on the population dynamics of the pest. Pest densities increased from 1.47 nymphs/leaf to 39.4 nymphs/leaf in the control, but were reduced to 0.8 and 0.6 nymphs/leaf in the cages where, respectively, 4 and 8 parasitoids were released per plant. It appears that parasitism is an important factor reducing B. tabaci populations during and after the cotton-growing season, and that Eretmocerus spp. are promising biological control candidates against the pest in cotton.     

棉田间作蔬菜防治B型烟粉虱

在室内用"Y"形嗅觉仪以棉花为对照测定了B型烟粉虱对6种蔬菜的选择性,不同蔬菜对B型烟粉虱诱集率的大小为:菜豆花生茴香芫荽芹菜韭菜。除了烟粉虱对菜豆的选择系数为正值外,烟粉虱对其他几种蔬菜的选择系数均为负值。6种蔬菜与棉花间作,结果表明:间作棉花上的烟粉虱成虫数量与对照存在显著差异。除了间作菜豆棉花上的烟粉虱成虫数量比对照增加外,间作花生、茴香、芫荽、芹菜、韭菜的棉花上烟粉虱成虫数量比对照均减少。     

Transmission of Tomato Yellow Leaf Curl Virus by two invasive biotypes and a Chinese indigenous biotype of the whitefly Bemisia tabaci

The global invasion of certain Bemisia tabaci biotypes provides opportunities to compare the competency of virus transmission between invasive and indigenous biotypes. Here we report on the acquisition, retention and transmission of Tomato Yellow Leaf Curl Virus (TYLCV) by the invasive B, Q and indigenous ZHJ2 biotypes of B. tabaci from Zhejiang, China. For all whitefly biotypes, TYLCV DNA was detected within a 30-min acquisition access period (AAP) to infected leaves. The percentage of adults with viral DNA increased with the length of AAP and reached 100% after 10–12 h. Following acquisition, viruliferous B, Q and ZHJ2 adults retained TYLCV DNA for the rest of their lives. Transmission was achieved with one B/Q adult per plant at the frequency of 50–55%, which rose to 100% with 10 insects per plant. In contrast, transmission of the virus was not observed with one ZHJ2 adult per plant in the experiments, and the transmission frequency rose to only 30–45% when whitefly adults increased to 5–10 per plant. These new data will help in the determination of the pest status of the whitefly biotypes as virus vectors in the regions of invasion, and so help in the development of management strategies.     

浅黄恩蚜小蜂寄生对烟粉虱海藻糖含量、酶活和热激蛋白表达水平的影响

本文以烟粉虱Bemisia tabaci Gennadius及其优势寄生蜂浅黄恩蚜小蜂Encarsia sophia (Girault & Dodd)为研究对象,测定了浅黄恩蚜小蜂寄生烟粉虱若虫后6、12、24、48和72 h,寄主体内海藻糖含量、海藻糖酶活性变化以及3种热激蛋白基因的即时表达情况.结果表明,自寄生蜂寄生后烟粉虱体内海藻糖含量先升高后降低,而海藻糖酶活性则先降低后升高,二者的变化拐点均表现在寄生后24 h.此外,寄生能够诱导烟粉虱hsp90过量表达,但同时抑制hsp70的表达.热激蛋白hsp20的表达量先升高后降低,且3种基因均在寄生后12h开始出现表达差异.本研究证明海藻糖和热激蛋白参与了寄生蜂与寄主互作体系,同时探讨了二者在寄生蜂与寄主互作过程中的具体作用,对于揭示寄生蜂-寄主互作机制有一定的参考价值.     

Biological control of potato soft rot caused by Dickeya solani and the survival of bacterial antagonists under cold storage conditions

Dickeya and Pectobacterium are responsible for causing blackleg of plants and soft rot of tubers in storage and in the field, giving rise to losses in seed potato production. In an attempt to improve potato health, biocontrol activity of known and putative antagonists was screened using in vitro and in planta assays, followed by analysis of their persistence at various storage temperatures. Most antagonists had low survival on potato tuber surfaces at 4 °C. The population dynamics of the best low-temperature tolerant strain and also the most efficient antagonist, Serratia plymuthica A30, along with Dickeya solani as target pathogen, was studied with TaqMan real-time PCR throughout the storage period. Tubers of three potato cultivars were treated in the autumn with the antagonist and then inoculated with D. solani. Although the cell densities of both strains decreased during the storage period in inoculated tubers, the pathogen population was always lower in the presence of the antagonist. The treated tubers were planted in the field the following growing season to evaluate the efficiency of the bacterial antagonist for controlling disease incidence. The potato endophyte S. plymuthica A30 protected potato plants by reducing blackleg development on average by 58.5% and transmission to tuber progeny as latent infection by 47–75%. These results suggest that treatment of potato tubers with biocontrol agents after harvest can reduce the severity of soft rot disease during storage and affect the transmission of soft rot bacteria from mother tubers to progeny tubers during field cultivation.