Garibaldi A, Bertetti D, Pensa P, Gullino M L
Center of Competence AGROINNOVA, University of Torino, Via Leonardo da Vinci, 44, 10095 Grugliasco, Italy.
Plant Dis. 2009 Jun;93(6):672. doi: 10.1094/PDIS-93-6-0672A.
Lampranthus sp. N.B. Brown (figmarigold) of the Aizoaceae family is used as groundcover in gardens. In October of 2008, severe outbreaks of a previously unknown rot were observed in a nursery located in Liguria, near Savona (northern Italy), on 35-day-old rooted cuttings grown in a peat substrate. Approximately 50% of rooted cuttings of red-flowered cultivars were affected. Lesions on collars and young stems were brown, water soaked, and soft. Plants eventually collapsed as roots rotted. Thin, aerial hyphae were visible on the surface of the stems and substrate. Later, a thick, light yellow, mycelial mat surrounded infected plants. Tissue fragments were excised from the margins of the lesions, dipped in a solution containing 1% sodium hypochlorite, and plated on potato dextrose agar and a medium selective for Oomycetes (4). Plates were incubated under constant fluorescent light at 23 ± 1°C for 4 to 5 days. Hyphae of five isolates grown on V8 medium were aseptate and 4.2 to 7.9 (average 6.2) μm wide. Sporangia consisted of complexes of swollen hyphal branches. Oogonia were globose, smooth, and 23.5 to 28.0 (average 25.9) μm in diameter. Antheridia were barrel shaped, intercalary, and diclinous. Oospores were globose and 19.4 to 23.6 (average 21.4) μm in diameter. The internal transcribed spacer (ITS) region of rDNA of a single isolate (DB24112008) was amplified with primers ITS4/ITS6 and sequenced. A BLAST analysis (1) in GenBank of the 1,074-bp segment showed a 100% homology with the sequence of Pythium aphanidermatum (Accession No. EU245039). The nucleotide sequence has been assigned the GenBank Accession No. FJ492745. Pathogenicity tests were performed twice on a red-flower cultivar of a Lampranthus sp. grown in 1-liter pots containing a peat moss substrate infested with wheat and hemp kernels colonized with one isolate of P. aphanidermatum at a rate of 20 g/liter. Ten plants were grown in infested media and 10 plants were grown in noninfested media. Greenhouse temperatures were 18 to 24°C. The first symptoms of stem and root rot developed 15 days later, while control plants remained healthy. P. aphanidermatum was consistently reisolated from the lesions. To our knowledge, this is the first report of P. aphanidermatum on a Lampranthus sp. in Italy. The disease has been reported in Japan (3) in 2008, while in the United States, a Pythium sp. was reported on L. aureus and L. glomeratus (2). Currently, the economic importance of Pythium rot on figmarigold in Italy is still limited. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) D. F. Farr et al. Fungi on Plants and Products in the United States. The American Phytopathological Society, St Paul, MN, 1989. (3) H. Kawarazachi et al. J. Gen. Plant Pathol. 74:94, 2008. (4) H. Masago et al. Phytopathology, 67, 425, 1977.
番杏科的露草属植物（松叶菊）被用作园林地被植物。2008年10月，在意大利北部萨沃纳附近利古里亚的一家苗圃中，观察到35日龄、种植在泥炭基质中的带根插条上爆发了一种此前未知的严重腐烂病。约50%的红花栽培品种带根插条受到影响。茎基部和幼茎上的病斑呈褐色，水渍状，质地柔软。植株最终因根部腐烂而倒伏。在茎和基质表面可见纤细的气生菌丝。后来，感染植株周围形成一层厚的浅黄色菌丝层。从病斑边缘切取组织碎片，浸入含1%次氯酸钠的溶液中，然后接种到马铃薯葡萄糖琼脂和一种对卵菌有选择性的培养基上（4）。平板在23±1°C的恒定荧光灯下培养4至5天。在V8培养基上生长的5个分离株的菌丝无隔膜，宽4.2至7.9（平均6.2）μm。孢子囊由肿胀的菌丝分支复合体组成。藏卵器球形，表面光滑，直径23.5至28.0（平均25.9）μm。雄器桶形，间生，异宗配合。卵孢子球形，直径19.4至23.6（平均21.4）μm。用引物ITS4/ITS6扩增单个分离株（DB24112008）rDNA的内部转录间隔区（ITS），并进行测序。在GenBank中对1074bp片段进行BLAST分析（1），结果显示与瓜果腐霉序列（登录号EU245039）的同源性为100%。该核苷酸序列已被赋予GenBank登录号FJ492745。对种植在装有泥炭藓基质的1升花盆中的一种露草属植物红花栽培品种进行了两次致病性测试，基质中接种了被瓜果腐霉一个分离株定殖的小麦和麻籽，接种量为20克/升。10株植物种植在接种基质中，10株植物种植在未接种基质中。温室温度为18至24°C。15天后出现茎腐和根腐的最初症状，而对照植株保持健康。从病斑中持续重新分离到瓜果腐霉。据我们所知，这是意大利关于瓜果腐霉侵染露草属植物的首次报道。2008年日本曾报道过这种病害（3），而在美国，曾报道过一种腐霉属真菌侵染金黄露草和聚花露草（2）。目前，瓜果腐霉对意大利松叶菊的经济重要性仍然有限。参考文献：（1）S.F.Altschul等人，《核酸研究》25:3389，1997。（2）D.F.Farr等人，《美国植物和产品上的真菌》。美国植物病理学会，明尼苏达州圣保罗，1989。（3）H.Kawarazachi等人，《植物病理学报》74:94，2008。（4）H.Masago等人，《植物病理学》67，425，1977。
