桃枝枯病病原鉴定

Identification of the pathogen causing shoot blight of peach trees

为明确近年来新发现的严重危害桃树的桃枝枯病病原种类,采集浙江和江苏两地的桃枝枯病病枝,对病原进行分离和鉴定。通过对真菌分离物培养性状、分生孢子器和分生孢子形态观察,两地真菌分离物均为桃拟茎点霉(Phomopsis amygdali)。ITS1-5.8SrDNA-ITS2序列分析表明两地真菌分离物为同一种病原菌,与GenBank中桃拟茎点霉序列具有99%的相似性,其ITS序列已在GenBank中登录(登录号分别为JX081273和JX182974)。离体和活体致病性测定结果表明,分离菌株均能使桃健康新梢产生枝枯病症状,从接种发病部位再次分离到病原菌,完成了柯赫氏法则(Koch’postulates)验证。结合其形态特征、ITS序列和致病性测定结果,浙江和江苏桃枝枯病病原确定为桃拟茎点霉。

ABSTRACT： Peach shoot blight is an increasingly serious and new disease in Zhejiang and Jiangsu province peach growing areas in recent years. The pathogen was isolated from peach twigs with constriction canker from peach orchards in Jiax- ing, Zhejiang province and Wuxi, Jiangsu province, respectively. Examination of the strains by morphological and cultur- al characteristics showed that the fungus was Phomopsis amygdali. The identification was verified by ITS analysis of rD- NA. The sequences （GenBank accession Nos. JX081273 and JX182974） shared 99.6% identity with each other. A com- parison of these two sequences with those in GenBank showed that the sequences had the highest nucleotide similarity （99%） with P. amygdali isolate FAU1052 from peach in the southeastern United States （accession No. AF102998）. Pathogenicity tests in vivo and in vitro indicated that the isolates caused similar reddish brown around twigs as observed in the field. The pathogen was reisolated from inoculated plants, confirming Koch＇s postulates. Based on the pathogenici- ty, morphological characteristics and rDNA molecular analysis, the pathogen of peach shoot blight was finally identified as P. amygdali.