从稻纵卷叶螟分离的一株微孢子虫的生物学特性与分子系统发育分析

Biological Characters and Molecular Phylogenetic Analysis of a Microsporidium Strain Isolated from Cnaphalocrocis medinalis

从来自广西壮族自治区的稻纵卷叶螟体内分离到1株微孢子虫,编号为CmM1。CmM1微孢子虫的孢子形状为卵圆形,大小为(1.71±0.16)μm×(2.82±0.22)μm;在生活史的各发育阶段均为双核,以二分裂方式增殖,发育周期为120 h;可以与家蚕微孢子虫(Nosema bombycis,Nb)抗血清产生阳性凝聚反应;超微结构具双核,极丝11～13圈。以上生物学性状显示CmM1微孢子虫具有微粒子属(Nosema)的基本分类特征。对CmM1微孢子虫的SSU rRNA基因序列进行PCR扩增与测序,并构建系统发育树及进行序列相似性和遗传距离的分析,进一步证实CmM1微孢子虫属于Nosema属,与家蚕微孢子虫的亲缘关系很近。将该微孢子虫暂命名为Nosema sp.CmM1。调查CmM1微孢子虫对稻田中的稻纵卷叶螟的自然感染率为3.68%～5.14%。CmM1微孢子虫对家蚕的半数感染浓度(IC50)为1.16×104mL-1,是Nb的0.47倍,对家蚕的平均胚种传染率为2.86%,说明CmM1微孢子虫对家蚕具有较强致病性和危害性。

A microsporidium strain,numbered as CmM1,was isolated from Cnaphalocrocis medinalis in Guangxi Zhuang Autonomous Region.The spore of CmM1 was oval in shape and（1.71±0.16） μm×（2.82±0.22） μm in size.CmM1 spore had two nuclei at all developmental phases of its life cycle and propagated in binary fission pattern.Its life cycle was about 120 h.It had positive coagulation reaction with the antiserum of Nosema bombycis（Nb）.Its ultrastructure was binuclear and had 11 ~13 polar filament coils.These biological characters indicated that CmM1 had the basic taxonomic features of Nosema.The SSU rRNA sequences of CmM1 were amplified by PCR and sequenced for constructing phylogenetic tree and for analyzing its similarity and genetic distance with other microsporidian strains,which further confirmed that CmM1 belonged to the genus of Nosema,and had close relationship with Nosema bombycis.Thus,this microsporidian strain was temporarily named as Nosema sp.CmM1.CmM1 had a natural infection rate of 3.68% to 5.14% to Cnaphalocrocis medinalis in paddy field.The 50% infectious concentration（IC50） of CmM1 to Bombyx mori was 1.16×104 mL-1,being 0.47 times to that of Nb.Its germinative infection rate to Bombyx mori was 2.86%,indicating that CmM1 is highly pathogenic and harmful to Bombyx mori.