Cacciola S O, Scibetta S, Martini P, Rizza C, Pane A
Dipartimento di Chimica Biologica, Chimica Medica e Biologia Molecolare, University of Catania, 95125 Catania, Italy.
Istituto Regionale per la Floricoltura, 18038 Sanremo, Italy.
Plant Dis. 2009 Nov;93(11):1216. doi: 10.1094/PDIS-93-11-1216C.
In the last 10 years, various species of Banksia (family Proteaceae) endemic to Australia have been introduced into Italy where cultivation as flower plants is expanding. In the spring of 2003, a decline associated with root and basal stem rot of 2- to 3-year-old plants of Banksia speciosa R. Br., B. baxteri R. Br., and B. prionotes Lindl. grown in the ground was observed in a commercial nursery in Liguria (northern Italy). Aboveground symptoms included leaf chlorosis and wilt. Plants collapsed within 1 to 2 weeks after the appearance of leaf symptoms. A Phytophthora species was consistently isolated from roots and basal stem on BNPRAH selective medium (3). On V juice agar (VA), axenic cultures obtained by single hyphal transfers formed stellate to radiate colonies with aerial mycelium; on potato dextrose agar (PDA). the colonies showed stoloniform mycelium. Minimum and maximum growth temperatures on PDA and VA were between 5 and 10°C and 38 and 40°C, respectively, with the optimum at 30°C on PDA (mean radial growth rate of 10 isolates ranged between 9.3 and 10.2 mm per day) and 25 to 30°C on VA (14 mm per day). In saline solution and soil extract, all isolates produced catenulate hyphal swellings and ellipsoid, nonpapillate, persistent sporangia. Sporangia in saline solution varied from 47 to 70 × 30 to 44 μm (mean l/b ratio of 1.5). All isolates were A mating type and produced oogonia with amphyginous antheridia when paired with A mating type of P. drechsleri Tucker on VA plus β-sytosterol (3). The electrophoretic patterns of total mycelial proteins and two isozymes (esterase and malate dehydrogenase) (2) of all isolates from Banksia plants were identical, but distinct from the patterns of isolates of other Phytophthora species, including P. drechsleri, P. megasperma sensu stricto, and P. sojae. Internal transcribed spacer (ITS) regions of rDNA were amplified with primers ITS4/ITS6 and sequences of two isolates, IMI 393960 from B. speciosa and 466/03 from B. baxteri (GenBank Nos. FJ648808 and FJ648809), were 100% identical to sequences of isolates identified as Phytophthora taxon niederhauserii Z. G. Abad and J. A. Abad (GenBank Nos. AY550916, AM942765, and EU244850). Pathogenicity tests were performed on 1-year-old potted plants of B. speciosa with isolates IMI 393960 and 466/03. Twenty plants per each isolate were transplanted into 12-cm-diameter pots containing infested soil prepared by mixing steam-sterilized sandy loam soil with 1% of inoculum produced on autoclaved wheat kernels. Twenty control plants were grown in autoclaved soil mix. Plants were kept in the greenhouse with natural light at 25 ± 2°C and watered to field capacity weekly. All Banksia plants transplanted in infested soil showed symptoms of wilt, leaf chlorosis, and basal stem rot within 2 to 3 weeks. Noninoculated plants remained healthy. P. taxon niederhauserii was reisolated solely from inoculated plants. P. taxon niederhauserii has been reported recently from Banksia spp. in Australia (1), but to our knowledge this is the first report from Italy. P. taxon niederhauserii may represent a threat to the cultivation of many ornamentals including Cystus spp., English ivy, and laurel (4). References: (1) T. I. Burgess et al. Plant Dis. 93:215, 2009. (2) S. O. Cacciola et al. EPPO Bull. 20:47, 1990. (3) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (4) E. Moralejo et al. Plant Pathol, 58:100, 2009.
在过去10年里，澳大利亚特有的多种山龙眼科佛塔树属植物被引入意大利，作为花卉植物种植的规模正在扩大。2003年春季，在利古里亚（意大利北部）的一家商业苗圃中，观察到种植在地里的2至3年生的壮丽佛塔树、巴氏佛塔树和长针佛塔树出现了与根和基部茎腐病相关的衰退症状。地上症状包括叶片黄化和枯萎。叶片症状出现后1至2周内植株就会倒伏。在BNPRAH选择性培养基上，始终能从根部和基部茎部分离出一种疫霉菌（3）。在V汁琼脂（VA）上，通过单菌丝转移获得的无菌培养物形成具气生菌丝的星状至辐射状菌落；在马铃薯葡萄糖琼脂（PDA）上，菌落呈现匍匐状菌丝。在PDA和VA上的最低和最高生长温度分别为5至10°C和38至40°C，在PDA上的最适温度为30°C（10个分离株的平均径向生长速率为每天9.3至10.2毫米），在VA上为25至30°C（每天14毫米）。在盐溶液和土壤提取物中，所有分离株都产生链状菌丝肿胀以及椭圆形、无乳突、持久的孢子囊。盐溶液中的孢子囊大小为47至70×30至44微米（平均长宽比为1.5）。所有分离株均为A交配型，当与VA加β - 谷甾醇上的德氏疫霉A交配型配对时，会产生具双游现象雄器的藏卵器（3）。来自佛塔树植物的所有分离株的总菌丝体蛋白和两种同工酶（酯酶和苹果酸脱氢酶）的电泳图谱相同，但与包括德氏疫霉、大豆疫霉和致病疫霉在内的其他疫霉属分离株的图谱不同。用引物ITS4/ITS6扩增rDNA的内部转录间隔区（ITS）区域，来自壮丽佛塔树的IMI 393960和巴氏佛塔树的466/03这两个分离株的序列（GenBank登录号FJ648808和FJ648809）与被鉴定为尼氏疫霉的分离株序列（GenBank登录号AY550916、AM942765和EU244850）100%相同。用分离株IMI 393960和466/03对1年生的盆栽壮丽佛塔树进行致病性测试。每个分离株的20株植物被移植到直径12厘米的花盆中，花盆中装有通过将蒸汽灭菌的沙壤土与1%在高压灭菌小麦粒上产生的接种物混合制备的感染土壤。20株对照植物种植在灭菌土壤混合物中。植物置于温室中，自然光下，温度为25±2°C，每周浇水至田间持水量。所有移植到感染土壤中的佛塔树植物在2至3周内都出现了枯萎、叶片黄化和基部茎腐病症状。未接种的植物保持健康。仅从接种植物中重新分离出尼氏疫霉。尼氏疫霉最近在澳大利亚的佛塔树属植物中被报道（1），但据我们所知，这是在意大利的首次报道。尼氏疫霉可能对包括岩蔷薇属植物、英国常春藤和月桂在内的许多观赏植物的种植构成威胁（4）。参考文献：（1）T. I. Burgess等人，《植物病害》93:215，2009。（2）S. O. Cacciola等人，《欧洲和地中海植物保护组织通报》20:47，1990。（3）D. C. Erwin和O. K. Ribeiro，《世界疫霉病》。美国植物病理学会，明尼苏达州圣保罗，1996。（4）E. Moralejo等人，《植物病理学》58:100，2009。
