矮化核桃枝枯病病原菌的形态与分子鉴定

Morphological and molecular identification of the pathogen of dwarfing walnut branch blight

为了明确河南省洛阳地区核桃枝条一种新病害的病原种类,对采自田间的典型症状枝条进行了常规组织分离,对单孢菌株进行了形态鉴定、rDNA ITS序列分析及致病性测定。结果表明,病原菌在PDA培养基上菌落初为白色,随着色素的积累,由中心向边缘变为灰绿色,再变成墨绿色,最终全部变成黑色;气生菌丝棉絮毛状,菌落边缘不整齐,近圆形或不规则形。分生孢子器散生或聚生,呈黑色小粒状,分生孢子器球形或近球形,深褐色,具孔口;分生孢子梗短缺,无色,杆状,末端产生分生孢子;分生孢子梭形、纺锤形,无色,无隔,基部钝圆,顶部稍尖,单孢(24.5～29.0)μm×(4.8～7.5)μm。离体枝条接种结果表明,该菌能侵染核桃枝条引起与田间相同的症状。据此将分离物鉴定为葡萄座腔菌Botryosphaeria dothidea。

In order to clarify the pathogen of a new disease of walnut branch in Luoyang, Henan province, routine tissue separation of typical symptomatic branches from the field was carried out, and the morphological identification, rDNA-ITS sequence analysis and pathogenicity determination were performed for single spore strains. The results showed that the colony of the pathogen was initially white in the PDA medium, and with the accumulation of pigment, it was gray-green from the center to the edge;then it turned atrovirens, and eventually it turned black;the aerial hyphae were floccular and hairy, with irregular colony edge and nearly round or irregular shape. Pycnidia were scattered or aggregated, with small black granules, spherical or nearly spherical, dark brown, with orifice;conidiophores were short, colorless, rod-shaped, and at the termina were conidia;conidium was fusiform, colorless, without septum, with obtuse-rounded base, slightly pointed apex, and single spores (24.5-29.0)μm×(4.8-7.5)μm. The results of inoculation in excised branches showed that the pathogen could infect the walnut branches and cause the same symptoms as those in the field. Accordingly, the isolate was identified as Botryosphaeria dothidea .