桃枝枯病的症状及其病原鉴定

Identification of the pathogen of peach branch blight

近年来,在浙江省重要的水蜜桃产区嘉兴凤桥镇、慈溪掌起镇等地发生了一种新的桃树病害———桃枝枯病。该病害引起桃树新梢嫩枝的基部位置出现环状棕褐色至黑褐色病斑,致使枝条病部以上叶片快速枯萎脱落,病害蔓延扩展迅速,可造成老枝的大量枯死,造成约20%～50%的产量损失,严重的致使桃树整株死亡。按柯赫氏法则对桃树病枝进行分离、纯化和致病性试验,明确桃枝枯病的病原为一种真菌,该真菌在PSA培养基上生长旺盛,菌丝为白色至淡橄榄色、短、微絮状,产生黑色球形分生孢子器,有孔口,产生两型分生孢子,α型分生孢子长纺锤形,无色,单孢,含有1～2个油球,(5.2～8.7)μm×(1.3～2.7)μm;β型分生孢子无色,线形,单孢,1～3个油球,(11.5～26.2)μm×(0.9～2.1)μm。对该菌的rDNA ITS进行PCR扩增,获得长度为611 bp的序列,经比对GenBank上的ITS序列数据,并结合形态特征,鉴定该病原真菌为半知菌亚门拟茎点霉属核果果腐拟茎点菌(Phomopsis amygdali Delacr.J.J.Tuset&M.T.Portilla)。

Peach branch blight, a serious new fungal disease, burst out in Fengqiao town, Jiaxing city and Zhangqi town, Cixi city in Zhejiang in recent years. The symptom firstly appeared on the base of shoot twig with tan to black pit scab causing the leaves above withering sharply. The disease cause death of branch even the whole peach tree, and reduced seed setting rate about 20% -50% per year. To understand and control the disease, Koch＇s postulate was used and a species＇ of fungus was found to be the pathogenic agent. The fungus yielded white to light olivesheen colony on potato saccharose agar （PSA） medium with short tiny cotton-shaped hypha, and produced black spherical pycnidium with ostiole. There were two kinds of condium generated by pathogen, α-type, fusiform, hyaline, unicellu- lar, （5.2 - 8.7） μm × （ 1.3 - 2. 7 ） μm ; 13-type, linear, hyaline, unicellular, 1 - 3 oil globule, （ 11.5 - 26. 2 ） μm × （0. 9 - 2. 1 ） μm. The ribosomal ITS 1-5.8S-ITS2 region was PCR amplified from genomic DNA from mycelium and obtained a sequence of 611 bp. A blast search from the GenBank revealed highest similarity （ 100% ） to Pho-mopsis amygdali sequences in Europe. The pathogen was identified as Phomopsis amygdali Delacr. J.J. Tuset ＆ M T. PortiUa （Fusicoccum amygdali Delacr. ） associated with culture characters.