沙里院褐球蚧蜜露对病原真菌蜡蚧轮枝菌侵染力的影响

Effect of Honeydew Excreted by Rhodococcus sariuoni on Infection Ability of Verticillium lecanii

蚧虫在取食和发育过程中排泄大量蜜露,通过研究蜜露对病原真菌侵染蚧虫的影响,可为应用病原真菌防治蚧虫提供科学依据.于2007年4月自山西省太原市苹果树上沙里院褐球蚧Rhodococcus sariuoni Borchsenius雌虫虫体表面采取蜜露,用化学分析方法和氨基酸自动分析仪测定其化学成份;将蜜露稀释为10%、20%、30%、40%、50%共5个浓度,对蜡蚧轮枝菌(Verticillium lecanii)的两个菌株No.V3.4504和No.V3.4505进行培养,比较其对菌株胞外蛋白酶和几丁质酶活性的影响.结果发现,该蚧虫蜜露包含可溶性糖(占69%)、水分(占26%)和18种氨基酸.当蜜露稀释浓度为10%时,菌株No.V3.4504的蛋白酶活性最大,为(4.45±0.18)U/mL;随着蜜露浓度增加,蛋白酶活性呈下降趋势;在蜜露浓度为20%时,菌株No.V3.4505的蛋白酶活性出现最大值,为(8.5±0.71)U/mL;随后,蛋白酶活性持续降低.两菌株几丁质酶的活性与蛋白酶活性有相同的变化趋势.在培养基中分别加入氨基酸Ala、Met、Gly、Pro,发现加入Met使菌株No.V3.4504和No.V3.4505的蛋白酶活性分别增长了256.9%和215.7%.表明低浓度的蜜露和培养基中加入适当Met能提高蜡蚧轮枝菌对蚧虫的侵染力.

Scale insects（Rhodococcus sariuoni Borchsenius）（Hemiptera：Coccidae）usually excrete large amount of honeydew when eating and developing.In this paper,the effect of the excreted honeydew on the infection ability of entomopathogenic fungi [Verticillium lecanii（Zimmermann）GamsZare]was studied for better use of entomopathogenic fungi to control scale insects. The honeydew in the experiment was collected in April,2007 from the female body surface of R.sariuoni in an apple orchard in Taiyuan,Shanxi Province,China.The chemical components of the honeydew were determined using chemical analysis and amino acid automatic analyzer.The honeydew was diluted into five concentrations of 10%,20%,30%,40% and 50%.Two V. lecanii strains,No.3.4504 and No.3.4505,were cultured in these honeydew solutions,respectively to compare their extracellular protease and chitinase activities.The results showed that the honeydew of R.sariuoni contained 69% soluble sugar,26% water and 18 amino acids.Strain No.3.4504 showed that the maximum value of its protease activity,（4.45±0.18）U/mL,cultured in the 10% honeydew solution,while in other 4 honeydew solutions,its protease activities decreased with increasing of honeydew concentrations.Comparatively,the value of strain No.3.4505 was higher,（8.5±0.71）U/mL,in 20% honeydew solution.Then, its protease activity went down with increasing of honeydew concentration.The chitinase activities of the two strains appeared a similar variation trend and their maximum activities all appeared when cultured with 10% honeydew solution.Four kinds of amino acids,Ala,Met,Gly and Pro were respectively added in the culture medium to test their effects on the protease activity of the entomopathogenic fungi.The results indicated that the addition of Met made the protease activities of the two strains increased by 256.9% and 215.7%,respectively,which showed that the honeydew at lower concentrations and appropriate Met in the culture medium could promote the infection of V.lecanii to the host scale insects.Fig 3,Tab 3,Ref 14