PDF(Pubmed)
Abstract：
Leaf-blight disease caused by the Fusarium oxysporum is an emerging problem in Dendrobium chrysotoxum production in China. Symptoms of leaf blight were observed on seedlings of D. chrysotoxum cultivated in a nursery in Ruili City, Yunnan Province, China. In this study, we isolated the Fusarium sp. associated with leaf-blight disease of D. chrysotoxum from the diseased seedlings. A pathogenicity test was performed to fulfill Koch\'s postulates to confirm the pathogenicity of isolated strains and identified using morphological and molecular techniques. The results revealed that all four isolated Fusarium sp. isolates (DHRL-01~04) produced typical blight symptoms followed by marginal necrosis of leaves on the D. chrysotoxum plants. On the PDA medium, the fungal colony appeared as a white to purplish color with cottony mycelium growth. Microconidia are oval-shaped, whereas macroconidia are sickle-shaped, tapering at both ends with 2-4 septations. The phylogenetic trees were construed based on internal transcribed spacer (ITS), translation elongation factor (EF-1α), and RNA polymerase subunit genes RPB1 and RPB2 genes, respectively, and blasted against the NCBI database for species confirmation. Based on the NCBI database\'s blast results, the isolates showed that more than 99% identify with Fusarium oxysporum. To our knowledge, this is the first comprehensive report on the identification of Fusarium oxysporum as the causal agent of Dendrobium chrysotoxum leaf blight in Yunnan Province, China, based on morphological and molecular characteristics.
摘要：
尖孢镰刀菌引起的叶枯病是中国铁皮石斛生产中的新兴问题。在瑞丽市苗圃种植的D.chrysothoum幼苗上观察到叶枯病的症状，云南省,中国。在这项研究中,我们分离了镰刀菌。与病苗中D.chrysotoxum的叶枯病有关。进行致病性测试以符合Koch的假设，以确认分离菌株的致病性，并使用形态学和分子技术进行鉴定。结果表明，所有四个分离的镰刀菌。分离株（DHRL-01〜04）产生典型的枯萎病症状，随后在D.chrysotoxum植物上叶片边缘坏死。在PDA介质上,真菌菌落呈白色至紫色，带有棉质菌丝生长。微分生孢子是椭圆形的,而大分生孢子是镰刀形的，在2-4隔的两端逐渐变细。系统发育树基于内部转录间隔区(ITS)进行解释，平移延伸因子(EF-1α)，和RNA聚合酶亚基基因RPB1和RPB2基因，分别,并对NCBI数据库进行了爆炸以进行物种确认。根据NCBI数据库的爆炸结果，分离株显示，超过99％的人鉴定为尖孢镰刀菌。据我们所知,这是云南省首份关于尖孢镰刀菌为铁皮石斛叶枯病致病因子的综合鉴定报告,中国,基于形态和分子特征。
