安徽省大豆疫霉根腐病菌的鉴定及rDNA-ITS序列分析

为明确安徽省夏大豆疫霉根腐病的病原菌种类,对采集自涡阳、怀远、固镇3个县的夏大豆病株及土样分离纯化后获得28株菌株,选取6株代表性菌株,通过形态学观察及核糖体DNA-ITS序列分析对其进行鉴定,并测定了其致病型。结果表明,6株菌株在利马豆培养基上菌落白色,质地均匀;菌丝无隔,致密,具近直角分枝;在10%V8C培养液中,游动孢子囊顶生,不脱落,卵形至椭圆形,无明显乳突,有内层出现象,长宽比大于1.6∶1;同宗配合,在利马豆培养基上单株培养产生大量卵孢子,藏卵器球形,雄器大多侧生;接种合丰35大豆品种后出现典型的大豆疫霉根腐病症状。r DNA-ITS序列分析表明,6株菌株与Gen Bank中大豆疫霉Phytophthora sojae的ITS序列同源性高达100%;菌株GY4、GY8、HY11、HY16、GZ10、GZ21的毒力公式分别为1b,2,3a,3b,4,5,6,7;1b,1d,3a,3b;1d,3a,3b,3c,4,5,6,7;2,3c,4,5,6,7;1b,3a,3c,5,8;3a,3b,5,6,7,8;属于6个不同的致病型。研究表明,这6株菌株均为大豆疫霉。

Identification and rDNA-ITS sequence analysis of the pathogen of soybean Phytophthora root rot in Anhui Province

In order to determine the pathogen of Phytophthora root rot on summer soybean in Anhui Province, the diseased samples from plants and soil were collected from Guoyang, Huaiyuan and Guzhen counties on soybean field. Six representative isolates were selected for identification after isolation and purification of the pathogen. The morphological characteristics, pathogenicity to soybean seedlings and ribosomal DNA-ITS sequences analysis were investigated with morphological observation. The results showed that the colonies of all the six isolates on LBA plates were white and round with uniform texture. The hyphae were nonseptate and dense with nearly right-angled branches. In 10% V8C broth, the sporangia were non-papillate, acrogenous, not deciduous, oviform to ellipsoidal and non-papillate with length/breadth ratios (L/B) over 1.6:1. Internal proliferation of sporangia could be observed. All isolates were homothallic with sexual organs abundant in single cultures. Oogonia were spherical or nearly spherical, and antheridia were mostly paragynous on LBA plates. The soybean seedlings of Hefeng 35 inoculated with the isolates showed the typical symptom of Phytophthora root rot. The sequences of ribosomal DNA-ITS of the six isolates were closest relative to that of Phytophthora sojae with 100% identity. The virulence formulas of GY4, GY8, HY11, HY16, GZ10, GZ21 were 1b,2,3a,3b,4,5,6,7; 1b,1d,3a,3b; 1d,3a,3b,3c,4,5,6,7; 2,3c,4,5,6,7; 1b,3a,3c,5,8; 3a,3b,5,6,7,8, respectively, and the six strains belonged to six different pathotypes. The results indicated that the six strains were identified as P.sojae.