坡面方胸材小蠹鉴定与风险分析

【目的】 杨树是我国主要的人工林造林树种,同时也是重要的绿化和用材树种。准确鉴定枯死杨树内小蠹虫的种类,并确定其在中国境内的风险大小,为该小蠹虫的防控提供理论参考。【方法】 采用传统的形态学鉴定方法,观察和测定小蠹虫(采自江苏东台林场枯死杨树内的样本虫株JSYC-beetle)头部、前胸背板、触角以及鞘翅等形态指标,初步判定小蠹虫的分类地位;使用CTAB法提取小蠹虫的基因组DNA,使用小蠹虫28S rDNA、COI和CAD基因引物分别对基因组DNA进行扩增,扩增产物经过生物公司测序、拼接,在NCBI网站进行同源性分析比对,选择同源性排名前10~15的相似序列,以NJ法分别构建3个基因系统进化树,根据系统进化树的聚类结果对小蠹虫JSYC-beetle进行分子鉴定。为预测小蠹虫的危害性,根据有害生物危险性评价定量分析方法对小蠹虫JSYC-beetle在中国的分布和潜在危害进行风险分析。【结果】 小蠹虫JSYC-beetle雌虫体色红褐色至黑色,体长3.3~3.7 mm,宽1.49~1.64 mm;雄虫体色黄褐色,体长2.264 mm,宽1.195 mm。虫体具有金属光泽,触角鞭节5节,第1节长度小于其余各节,触角末节球状,有2条明显的横缝。复眼肾形,头部藏在前胸背板下,前胸背板近方形,凸出明显,前缘阔圆形,宽略大于长,前半部分分布鳞状齿,后半部分光滑。小盾片舌状,鞘翅宽略大于前胸背板的宽度,鞘翅斜面从基部至端部逐渐倾斜,鞘翅轮廓如舌,鞘翅列间部上的刻点与沟内刻点大小相近,分布均匀,鞘翅茸毛长。前足胫节具有8~14个齿瘤不等,第1跗节小于其余跗节长度之和。以上形态比对结果表明小蠹虫JSYC-beetle的形态特征与坡面方胸材小蠹形态特征最为相似;28S rDNA、COI和CAD基因扩增产物经琼脂糖凝胶电泳结果表明,3对引物均能扩增出单一、明亮条带,其中COI 基因扩增出的条带大小在700~1 000 bp,28S rDNA基因扩增的条带大小约为500 bp, CAD 基因扩增出的条带大小在400~500 bp。NCBI序列比对结果显示COI、28S rDNA以及CAD序列均与坡面方胸材小蠹同源性最高,其相似性依次为99.14%、99.38%和99.36%;以NJ法构建的系统进化树结果显示小蠹虫JSYC-beetle均与坡面方胸材小蠹虫聚在一个分支上,进一步表明小蠹虫JSYC-beetle虫株与坡面方胸材小蠹关系最近,基于小蠹虫JSYC-beetle虫株形态学和分子生物学鉴定结果,最终将枯死杨树内小蠹虫JSYC-beetle虫株鉴定为坡面方胸材小蠹。风险分析结果显示坡面方胸材小蠹风险R值为2.01,在我国属于高危险度生物。【结论】 实验使用小蠹虫是从杨树林采集,经鉴定枯死杨树内小蠹虫为坡面方胸材小蠹,该生物在中国境内属于高危生物,已报可能危害健康杨树。采集地有大量杨树死亡,因此需要加强管理,以防止该生物对杨树及其他寄主植物造成重大危害。

Identification and risk analyses of Euwallacea interjectus

【Objective】 Poplars are important tree species in plantations and timber in China. We aimed to identify the species of the JSYC-beetle strain in dead poplar and determine its risk, and provide a theoretical reference for the control of the beetle. 【Method】 The head, pronotum, antennae and elytron of the beetle were observed and measured by the traditional morphological identification method. The DNA of the beetle was extracted by using the CTAB method, and the corresponding COI, 28S rDNA and CAD regions were amplified. The amplified products were sequenced and spliced by biological companies, homology analysis was conducted on the NCBI website, and similar sequences with the top 10-15 homology were selected to construct three gene phylogenetic trees by using the NJ method. According to the clustering results of the phylogenetic tree, JSYC-beetle strain were identified. In order to predict the possible damage degree, the distribution and potential hazards of the JSYC-beetle in China were analyzed according to the quantitative analysis method of pest risk assessment.【Result】 The female JSYC-beetle was reddish-brown to black, with a body length of 3.3-3.7 mm and a width of 1.49-1.64 mm. The male was yellowish-brown, with a body length of 2.264 mm and a body width of 1.195 mm. The insect body had a metallic luster. The flagellum had five segments, and the length of the first segment was shorter than that of the other segments. The end segments of the antennae were spherical, with two obvious transverse seams. The compound eyes were kidney shaped. The head was hidden in the anterior sternal plate. The anteroposterior plate was nearly square in shape and protrudes. The front edge was wide and round, and its width was slightly larger than its length. The front part was distributed with squamous teeth, and the latter part was smooth. The scutellum was ligulate, and the width of the elytron was slightly larger than that of the pronotum. The oblique plane of the elytron gradually inclinesd from the base to the end. The elytron was shaped similarly to a tongue. The size of the incisions on the intercostal part of the elytron was similar to that in the groove, and the distribution was uniform. There were 8-14 odontomas in the tibial segment of the forefoot, and the first segment of the trasi was shorter than the sum of the other segment lengths. According to the aforementioned morphological comparison, the morphological characteristics of the bark beetle JSYC-beetle strain were most similar to those of E. interjectus. The COI, 28S rDNA and CAD genes were amplified by agarose gel electrophoresis. The results showed that COI, 28S rDNA and CAD genes could amplify single and bright bands and that the size of the electrophoresis band was 700-1 000 bp, approximately 500 bp and 400-500 bp, respectively. The results of NCBI sequence alignment showed that the COI, 28S rDNA and CAD sequences had the highest homology with E. interjectus, with similarities of 99.14%, 99.38% and 99.36%, respectively. The phylogenetic tree showed that the JSYC-beetle strain was clustered in one branch with E. interjectus, further indicating that the JSYC-beetle had the closest relationship with E. interjectus. On the basis of these results, the JSYC-beetle was identified as E. interjectus. The results of risk analysis showed that the risk R value was 2.01, which was a high-risk organism in China. 【Conclusion】 The bark beetles in dead poplar trees are E. interjectus, a high-risk organism in China. The beetle may harm healthy poplar and has been collected from poplars in China; there are many dead poplars in the collection area. Therefore, strengthening management to prevent major harm to poplar and other host plants is necessary.