来自景天科科的Graptoveria\''银星\''(介于丝虫和Echeveriaagavoides之间的杂交),是一种常绿的多汁植物,有莲花星座状的花朵,使其成为韩国消费者最喜欢的观赏植物。2019年,韩国的观赏产量估计为5174亿韩元(3.82亿欧元),根据农业部的数据,从4,244公顷的耕地面积中,韩国的食品和农村事务。2023年7月,Graptoveria\'银星\'植物与褪绿的叶子,在永宁(37°14\'27.9\'N,127°10'39.19''E),韩国。为了隔离因果代理,小片(1mm2)的有症状的组织使用1%NaOCl表面灭菌1分钟,然后放在水琼脂(WA)平板上,在25℃黑暗中孵育五天。从病叶中获得两个分离物(FD00202,FD00203),通过分离单个孢子囊的茎和根。为了研究分离株的形态特征,将来自马铃薯葡萄糖琼脂(PDA)的菌丝体转移至V8琼脂(V8A),随后在25°C下在黑暗中孵育7天。分离株产生了致密的棉质菌丝体,略带花瓣状和浅玫瑰花结图案,珊瑚状边缘测量70至83毫米直径。孢子囊为球形(30.0-48.0µm长,25.0-35.0µm宽),带有球形衣原体孢子(17.0-50.0µm长,18.0-38.0µm宽)。未观察到Oogonia。这些分离株的形态和文化特征在表型上与烟草疫霉相似(Faedda等人。2013;Abad等人。2023年)。对于分子鉴定,使用Maxwell®RSCPureFoodGMO和鉴定试剂盒(Promega)从5天龄培养物中提取基因组DNA。两个基因区,rDNA-ITS,分别使用引物ITS1/ITS4和FM83/FM84对COXI进行扩增和测序(White等人。1990年;马丁和图利2003年)。将所得序列保存在GenBank中,登录号为。LC783858到LC783861。对ITS的DNA序列进行BLASTn搜索,COXI与烟草分离株IMI398853的同一性分别为99.81%和98.94%。对ITS的组合数据集进行了最大似然系统发育分析,COXI在Tamura-Nei模型下使用MEGA7(Kumar等人,2016)。这些分离株与烟草分离株IMI398853、CPHSTBL162和CPHSTBL44形成单系群。根据形态特征和分子分析,该分离株被鉴定为烟草假单胞菌。T确认它们的致病性,接种物根据Ann(2000)制备。将人工受伤的健康植物根部浸入游动孢子悬浮液(3.0×106游动孢子/ml)中24小时,用模拟处理的植物(对照)浸入无菌蒸馏水(安。2000).此后,将植物移植到新培养基中并保持在高湿度下。在孵育10天后观察到症状。接种烟草的植物表现出与根腐病和颈腐病相似的褪绿叶症状,而控制保持无症状。从所有接种的植物中重新分离病原体,并通过形态学和分子分析确认为烟草假单胞菌。但不是来自控制,履行科赫的假设。烟草疫霉先前曾在加利福尼亚和韩国的Echeveriadenbergii和Kalanchoeblossfeldiana上报道过,在茎和根上引起褐斑,分别(法语1989年;哦和儿子2008年)。据我们所知,这是在韩国的葡萄树\“银星\”植物上引起根和领腐烂的第一份报告。
⨯Graptoveria \'Silver Star\' (a cross between Graptopetalum filiferum and Echeveria agavoides) from the
Crassulaceae family, are an evergreen succulent with lotus constellation-shaped flowers, making it consumer favorite ornamental plant in Korea. In 2019, Korea\'s ornamental production was estimated at KRW 517.4 billion (EUR 382 million), from 4,244 ha of farming area according to the Ministry of Agriculture, Food and Rural Affairs of Korea. In July 2023, ⨯Graptoveria \'Silver Star\' plants with chlorotic leaves, root and collar rot were observed in a greenhouse in Yongin (37°14\'27.9\"N, 127°10\'39.19\"E), Korea. To isolate the causal agent, small pieces (1 mm2) of symptomatic tissues were surface-sterilized using 1% NaOCl for 1 min, then put onto a water agar (WA) plate and incubated in the dark at 25℃ for five days. Two isolates (FD00202, FD00203) were obtained from diseased leaves, stem and roots by isolating single sporangium. To investigate the morphological characteristics of the isolates, the mycelium from potato dextrose agar (PDA) were transferred to V8 agar (V8A) followed by incubation at 25°C in the dark for 7 days. The isolates produced dense cottony mycelium, with slightly petaloid and light rossette pattern, with coralloid edges measuring 70 to 83 mm diameter. Sporangium were spheroid (30.0-48.0 µm long, 25.0-35.0 µm wide) with globose chlamydospores (17.0-50.0 µm long, 18.0-38.0 µm wide). Oogonia were not observed. Morphological and cultural characteristics of these isolates were phenotypically similar to that of Phytophthora nicotianae (Faedda et al. 2013; Abad et al. 2023). For molecular identification, genomic DNA was extracted from 5 days old cultures using the Maxwell® RSC PureFood GMO and Authentication Kit (Promega). Two gene regions, the rDNA-ITS, COX I were amplified and sequenced using primers ITS1/ITS4 and FM83/FM84, respectively (White et al. 1990; Martin and Tooley 2003). The resulting sequences were deposited in GenBank with accession no. LC783858 to LC783861. A BLASTn search of the DNA sequences from ITS, COX I showed 99.81 and 98.94% identity to P. nicotianae isolate IMI 398853, respectively. Maximum likelihood phylogenetic analyses were performed for the combined data set with ITS, COX I using MEGA7 under the Tamura-Nei model (Kumar et al. 2016). The isolates formed a monophyletic group with P. nicotianae isolate IMI 398853, CPHST BL162, and CPHST BL 44. Based on morphological characteristics and molecular analysis, the isolates were identified as P. nicotianae. T confirm their pathogenicity, inoculum was prepared in accordance with Ann (2000). Artificially wounded healthy plant roots were dipped in zoospore suspension (3.0 × 106 zoospore/ml) for 24 hours, with mock-treated plants (control) dipped in sterile distilled water (Ann. 2000). Thereafter, the plants were transplanted into new medium and kept under high humidity. Symptoms were observed after 10 days of incubation. The plants inoculated with P. nicotianae showed similar symptoms of chlorotic leaves with root and collar rot, while control remained symptomless. The pathogen was re-isolated from all inoculated plants and confirmed as P. nicotianae by morphological and molecular analysis. but not from controls, fulfilling Koch\'s postulates. Phytophthora nicotianae was previously report on Echeveria derenbergii and Kalanchoe blossfeldiana causing brown spot on stems and roots in California and Korea, respectively (French 1989; Oh and Son 2008). To best of our knowledge, this is the first report of P. nicotianae causing root and collar rot on ⨯Graptoveria \'Silver Star\' plants in the Korea.