梨花迁粉蝶微孢子虫对家蚕的侵染力与胚传性

Infectivity and transmissibility of Nosema sp. CP isolated from Catopsilia pyranthe( Lepidoptera: Pieridae ) in the domestic silkworm( Bombyx mori)

【目的】对梨花迁粉蝶Catopsilia pyranthe分离的微孢子虫进行形态与分子鉴定,探究其对非天然宿主家蚕Bombyx mori的侵染力与胚传性。【方法】从田间采集的梨花迁粉蝶中分离得到梨花迁粉蝶微孢子虫液,测定其孢子的形态、大小、体积、长短轴比,同时对该孢子虫的16S r DNA进行PCR克隆测序与分析。将梨花迁粉蝶微孢子虫Nosema sp.CP与家蚕微孢子虫N.bombycis分别对2龄起蚕、4龄起蚕进行添食感染比对,测定家蚕食下两种微孢子虫的感染率和胚种传染能力。【结果】本研究分离的梨花迁粉蝶微孢子虫形态为长椭圆形,具双核;其16S r DNA序列与已报道的梨花迁粉蝶微孢子虫的序列一致性大于99%,为梨花迁粉蝶微孢子虫。梨花迁粉蝶微孢子虫和家蚕微孢子虫对家蚕综合感染率分别是68.8%和98.3%;在继代蚁蚕中,感染梨花迁粉蝶微孢子虫和家蚕微孢子虫的雌蛾所产蚕卵次代蚁蚕检出有孢子虫的检出率分别为100%和100%,卵壳的孢子虫的检出率分别为92.9%和100%;梨花迁粉蝶微孢子虫和家蚕微孢子虫对家蚕的胚种传染力分别为9.6%和23.2%。【结论】本研究分离得到的微孢子虫为梨花迁粉蝶微孢子虫,具有微孢子虫Nosema属的典型特征。梨花迁粉蝶微孢子虫能感染危害家蚕,也具有家蚕胚种传染性,但感染率和胚传率均明显低于家蚕微孢子虫,是蚕业生产中必须防控的对象。

【Aim】To identify the morphological and molecular characteristics of microsporidium Nosema sp. CP isolated from Catopsilia pyranthe,and then to assess the infectivity and transmissibility of this Nosema sp. CP in the domestic silkworm,Bombyx mori. 【Methods】After purification of Nosema sp. CP spores isolated from wild C. pyranthe butterflies,the shape,sizes and axial ratios of the spores were measured under the microscope,respectively. The DNA fragments of 16 S rDNA from this microsporidian species were amplified by PCR and then sequenced to confirm its classification status. The Nosema sp.CP isolated and N. bombycis was fed respectively to B. mori larvae of day-1 2nd instar and day-1 4th instar to survey the infectivity and transmissibility via embryo during different developmental stages of B.mori. 【Results】Oblong shape and diplokaryotic nuclei of the isolated microsporidia in this study were visualized under the microscope. Molecular analysis of 16 S rDNA sequence showed more than 99%identity to that of the previously reported microsporidian spores isolated from C. pyranthe. The total infection rates of Nosema sp. CP and N. bombycis to B. mori were 68. 8% and 98. 3%,respectively. In the second generation of B. mori after vaccination,the detection rates of sporozoans of Nosema sp. CP and N. bombycis in newly-hatched larvae were 100% and 100%,and those of their eggshells were 92.9% and 100%,respectively. The embryo transmissibilities of Nosema sp. CP and N. bombycis to B.mori were 9. 6% and 23. 2%,respectively. 【Conclusion】The microsporidia isolated in this study are Nosema sp. CP and have typical characteristics of Nosema diplokaryotic nuclei. The Nosema sp. CP isolated can infect B. mori and has transmissibility via embryo in this insect. However,in B. mori both the infection rate and transmission rate of Nosema sp. CP isolated in this study are lower than those of N.bombycis. Thus,it is necessary to prevent and control the prevalence of Nosema sp. CP in sericultural industry.