广州地区一品红细菌性叶斑病的病原鉴定

Identification of pathogen causing bacterial leaf spot of Euphorbia pulcherrima in Guangzhou area

对广州地区一品红(Euphorbia pulcherrima)细菌性叶斑病的病原菌进行了分离、致病性测定、生理生化性状测定及16S rDNA序列分析.结果表明,该病原菌(YPH1菌株)为革兰氏阴性,好氧生长,在KB培养基上不产生荧光色素,在YDC平板上菌落呈黄色,在33℃下可生长,其16S rDNA序列(1 461 bp,GenBank登录号:KC841470)与GenBank中8株地毯草黄单胞菌(Xanthomonas axonopodis)序列相似性达99.7%以上;将这些相关细菌构建系统发育树,该病原菌与7株地毯草黄单胞菌在同一分支上,故将其初步鉴定为地毯草黄单胞菌(X.axonopodis).

A causal which occurred in G agent of bacterial leaf spot of Euphorbia pulcherrima was isolated and identified, uangzhou, Guangdong Province in recent years. The pathogenicity test, physiologi- cal and biochemical characteristics tests, 16S rDNA sequence analysis were undertaken to elucidate the precise position of the causal bacterium. The results indicated that the pathogen showed Gram＇s negative reaction and aerobic growth and yellow colony. The pathogen produced fluorescent pigment and could grow well at the temperature of 33 ~C. 16S rDNA sequence identity between the isolated pathogenic strain YPH1 （GenBank accession No. KC841470） and 8 strains of Xanthomonas axonopodis was more than 99.7%. By construction of their phylogenetic tree using neighbor-joining method in MEGA 4.0 software based on 16S rDNA sequence, the YPH1 strain and the other 7 strains of X. axonopodis belonged to a clade. The isolated pathogen was primarily identified as a X. axonopodis.