福建省大豆疫病病原鉴定及其核糖体DNA-ITS序列分析

 从福建省龙海大豆根腐病株上分离的疫霉菌株中,选取6个代表菌株,对病原菌进行了形态特征、致病性、寄主范围鉴定及核糖体DNA-ITS序列分析,结果表明,该菌为疫霉属真菌,在黑麦琼脂培养基上生长缓慢,菌丝致密、无隔,形成菌丝膨大体,近直角分支,分支处稍缢缩。水培后产生大量椭圆形孢子囊,不形成乳突,通过内层出方式产生新孢子囊,游动孢子在孢子囊内形成,同宗配合,藏卵器球形,雄器侧生;接种后可出现典型的大豆疫病症状;人工接种只侵染大豆、豇豆和菜豆等少数豆科植物。其核糖体DNA-ITS序列分析表明,分离菌株与GenBank中大豆疫霉的ITS序列的同源性均为99.8%,仅有2个碱基的差异,结合形态特征和致病性测定,将这些病原菌鉴定为Phytophthora sojae. 这是首次报道大豆疫霉菌在福建省存在。

Identification and sequencing of ribosomal DNA-ITS of Phytophthora sojae in Fujian

Six typical Phytophthora strains which cause soybean root rot in Longhai, Fujian were chosen for identification. The morphological characteristics, pathogenicity, host range and the sequence of ribo-somal DNA-ITS were studied. Based on its abundant, rounded hyphal swellings in chains, right-angle and shrinking in branch, non-papillate, ovoid sporangium, internal proliferation of sporangiophore, zoospores formed within sporangium, homothallism, rounded oogonia and paragynous antheridium as well as its narrow host range, the symptom of Soybean Phytophthora blight after inoculation, the pathogen was identified as Phytophthora sojae. The sequence of ribosomal DNA-ITS of Fujian isolates was closest relative to that of P.sojae published in GenBank with 99. 8% identity. The results indicated that these strains were P. sojae. This is the first report that P. sojae exits in Fujian, China.