Garibaldi A, Gilardi G, Poli A, Gullino M L
AGROINNOVA, Università di Torino Via Leonardo da Vinci 44, 10095 Grugliasco, Italy.
Plant Dis. 2011 Apr;95(4):496. doi: 10.1094/PDIS-12-10-0872.
In the summer of 2009, a wilt of chicory was observed on 25 to 30% of 30-day-old Cichorium intybus L. cv. Clio plants grown outdoors on a commercial farm in Piedmont (northern Italy). Affected plants were chlorotic and stunted with poorly developed root systems compared with healthy plants. Black streaks were observed in the stem and proximal part of the leaf vascular system in wilted plants. Fusarium oxysporum Schltdl. was isolated from symptomatic vascular tissue on a Fusarium-selective medium (1) from 80% of samples. Grown on potato dextrose agar (PDA) for 4 days at 23°C, the colonies, initially white and later pale pink, produced hyaline microconidia that were oval-elliptical and cylindrical in shape measuring 5.6 to 14.9 (average 10.2) × 2.1 to 4.5 (3.0) μm, borne on short monophialides measuring 8.2 to 16.1 (average 13.2) × 2.1 to 4.2 (3.3) μm. Macroconidia were slightly curved, three-septate, with a slightly hooked apical cell and a foot-shaped basal cell measuring 24.9 to 41.6 (average 32.2) × 3.2 to 5.2 (4.3) μm. Chlamydospores were both terminally and intercalary, solitary but also in short chains (2 to 4 elements) measuring 21.1 to 41.0 (average 27.2) μm (2). The internal transcribed spacer (ITS) rDNA region was amplified using the primers ITS1/ITS4 and sequenced. BLASTn analysis of the 527-bp amplicon (GenBank Accession No. HQ644423) obtained had 98% sequence identity with F. oxysporum (GenBank Accession No. FJ605247). The translation elongation factor-1α (EF-1α) gene was amplified using primers EF-1/EF-2 and sequenced (GenBank Accession No. GU564259). The 663-bp fragment had 99% sequence identity with F. oxysporum (GenBank Accession Nos. EU313540, EU313539, and DQ837696). Pathogenicity tests were conducted on 15-day-old chicory plants from two cultivars (Clio and Katia). Thirty-five plants per cultivar were inoculated by dipping their roots in a 1 × 10 CFU/ml suspension of isolate FusCic45B recovered from wilted chicory. Inoculated and noninoculated plants were transplanted into five pots filled with 10 liters of steamed mix (peat/perlite/sand, 60:20:20 vol/vol) and were maintained in a glasshouse at 25 to 27°C. Wilt symptoms and vascular discoloration of the roots, crown, and veins developed 15 days after inoculation on all inoculated plants. Plants of cv. Clio were more susceptible. F. oxysporum was always reisolated from infected plants using the Fusarium-selective medium. All noninoculated plants remained healthy. The pathogenicity test was conducted twice. To our knowledge, this is the first report of wilt caused by F. oxysporum on chicory, C. intybus, in Italy as well as worldwide. References: (1) H. Komada. Rev. Plant Prot. Res. 8:114, 1975. (2) E. Nelson et al. Fusarium Species: An Illustrated Manual for Identification. The Pennsylvania State University Press, University Park, 1983.
2009年夏天，在意大利北部皮埃蒙特一个商业农场户外种植的30日龄菊苣属（Cichorium intybus L.）品种克利奥（Clio）植株中，有25%至30%出现了萎蔫症状。与健康植株相比，受影响的植株黄化且生长受阻，根系发育不良。在萎蔫植株的茎和叶片维管束系统的近端观察到黑色条纹。从80%的样本中，在镰刀菌选择性培养基（1）上从有症状的维管组织中分离出尖孢镰刀菌（Fusarium oxysporum Schltdl.）。在马铃薯葡萄糖琼脂（PDA）上于23°C培养4天，菌落最初为白色，后来变为浅粉色，产生透明的小型分生孢子，呈椭圆形至圆柱形，大小为5.6至14.9（平均10.2）×2.1至4.5（3.0）μm，着生于短的单瓶梗上，单瓶梗大小为8.2至16.1（平均13.2）×2.1至4.2（3.3）μm。大型分生孢子略弯曲，有三个隔膜，顶端细胞略呈钩状，基部细胞呈足形，大小为24.9至41.6（平均32.2）×3.2至5.2（4.3）μm。厚垣孢子既有顶生的也有间生的，单个存在，但也形成短链（2至4个细胞），大小为21.1至41.0（平均27.2）μm（2）。使用引物ITS1/ITS4扩增内部转录间隔区（ITS）rDNA区域并进行测序。对获得的527 bp扩增子（GenBank登录号HQ644423）进行BLASTn分析，结果显示与尖孢镰刀菌（GenBank登录号FJ605247）有98%的序列同一性。使用引物EF-1/EF-2扩增翻译延伸因子-1α（EF-1α）基因并进行测序（GenBank登录号GU564259）。663 bp的片段与尖孢镰刀菌（GenBank登录号EU313540、EU313539和DQ837696）有99%的序列同一性。对来自两个品种（克利奥和卡蒂亚）的15日龄菊苣植株进行致病性测试。每个品种35株植株通过将其根部浸入从萎蔫菊苣中分离得到的菌株FusCic45B的1×10 CFU/ml悬浮液中进行接种。接种和未接种的植株被移植到五个装有10升蒸汽混合基质（泥炭/珍珠岩/沙子，60:20:20体积比）的花盆中，并在25至27°C的温室中养护。接种后15天，所有接种植株均出现萎蔫症状以及根部、冠部和叶脉的维管束变色。克利奥品种的植株更易感病。使用镰刀菌选择性培养基总是能从感染植株中重新分离出尖孢镰刀菌。所有未接种的植株保持健康。致病性测试进行了两次。据我们所知，这是意大利以及全球范围内关于尖孢镰刀菌引起菊苣（C. intybus）萎蔫的首次报道。参考文献：（1）H. Komada. Rev. Plant Prot. Res. 8:114, 1975.（2）E. Nelson等人. Fusarium Species: An Illustrated Manual for Identification. The Pennsylvania State University Press, University Park, 1983.
