一种新发生的油桐叶枯病病原真菌

A new leaf blight pathogen of Vernicia fordii

报道了中国广西田林县油桐主产区一种新的叶片真菌病害,定名为油桐叶枯病。该病主要为害叶片,病菌侵染后叶片呈现灰褐色病斑,后期扩至整个叶片,引起过早脱落,影响油桐产量。从采集的带病标本中分离到16个纯培养物,隶属5个分类单元。依据柯赫法则和致病性测定,证明只有菌株VT-04为油桐叶枯病的病原物。在病斑组织中观察不到有性或无性繁殖结构,而该病原菌在诱导培养(含无菌松针的水琼脂+近紫外照射)条件下可产生子实体。比较培养性状、产孢结构特征并结合分析核糖体rDNA基因转录间隔区(ITS)和RNA聚合酶次大亚基基因(RPB2)序列和系统发育关系,将该病原菌鉴定为葡萄座腔菌科Botryosphaeriaceae中的一种无性型菌物,即小新壳梭孢Neofusicoccum parvum。这是首次在油桐叶片上发现由该病菌引起的病害。

A new leaf blight pathogen of Vernicia fordii was recorded in Guangxi,China.The diseased leaves show dark brown spots which then spread over the whole leaves.The premature defoliation may significantly reduce the production of tung seeds.Sixteen pure fungal cultures belonging to five taxa were obtained from diseased leaf tissues.Strain VT-04 was identified as the pathogen based on Koch’s postulates and pathogenicity test.Fruiting structures had not been observed on clinic specimens,but induction of sporulation was successfully achieved when the pathogen was cultured on water agar medium containing sterile pine needles under UV light.An integrated analysis of cultural characteristics and phylogeny of two molecular markers including the ribosomal DNA internal transcribed spacer （ITS） and RNA polymerase II second largest subunit （RPB2） revealed that the pathogen was conspecific with Neofusicoccum parvum.This is the first report that N.parvum can cause leaf disease of V.fordii.