Three filamentous fungal strains were isolated form Carassius auratus eggs with Saprolegniasis, and strain JL1 was proved to be pathogenic to Carassius auratus eggs by artificial infection.Therefore, morphology and growth characteristics of strain JL1 were studied, and the phylogenetic analysis based on its ITS rDNA sequence was further conducted. The experimental results showed that the hyphae of strain JL1 was aseptate, transparent and seldom branched. Its zoosporangia were often clavate and renewed internally. Primary zoospore was multi-row arrangement in zoosporangia and discharged in Saprolegnia fashion. Spherical oogonia was attached by monoclinous or diclinous antheridium hyphae. The ITS rDNA sequences of strain JL1 was naturally clustered with ITS rDNA sequences of Saprolegnia sp. submitted to GenBank with 99％ of homology, and had closest relationship with Saprolegnia sp. H (accession number: EF460351). Combined morphological characterization with phylogenetic analysis based on ITS rDNA sequence, strain JL1 was identified as Saprolegnia sp.. In addition, strain JL1 could grow at 5℃-30℃ and pH 4-11, its optimum growing temperature and pH were 25 ℃-30℃ and 6-9, respectively. Strain JL1 was sensitive to sodium chloride, its growth could be completely inhibited by 2％ NaCI, which could serve as a foundation for the Saprolegniasis control.%从患病的彭泽鲫卵上分离3 株丝状真菌,经人工感染试验证实其中1 株丝状真菌JL1 对彭泽鲫卵具有致病性,并进一步研究了其形态与生长特性,开展了ITS rDNA 序列分析.实验结果表明,菌株JL1 菌丝为透明管状结构,中间无横隔,分枝较少; 游动孢子囊多数呈棒状,游动孢子呈多排排列,发育成熟后从孢子囊中释放出来,并迅速游离; 藏卵器呈球形,与雄器同枝或异枝.菌株JL1 的ITS rDNA 序列与GenBank 基因库中水霉属菌株自然聚类,同源性高达99%,与Saprolegnia sp.H (登录号:EF460351)的亲缘关系最近.结合形态特征与ITS 序列鉴定的结果,判定菌株JL1 为水霉菌(Saprolegnia sp.).此外,菌株JL1 在5°C-30°C、pH 4-11 范围内均能生长,最适生长温度和pH 范围分别为25°C-30°C 和6-9.同时菌株JL1 对NaCl 敏感,质量分数为2%的NaCl 即可抑制其生长,可以作为该病防治的依据.
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