Wang R-Y, Gao B, Li X-H, Ma J, Chen S-L
Institute of Plant Protection, Hebei Academy of Agricultural and Forestry Sciences, IPM Center of Hebei Province, Key Laboratory of Integrated Pest Management on Crops in Northern Region of North China, Ministry of Agriculture, Baoding, Hebei, China. This study was supported by the China Agriculture Research System (CARS-11-B-08).
Plant Dis. 2014 Jan;98(1):160. doi: 10.1094/PDIS-06-13-0651-PDN.
China is the biggest sweet potato (Ipomoea batatas (L.) Lam) producer in the world and its total production is about 100 million tons per year. Surveys for diseases of sweet potato in storage were conducted from 2011 to 2013 in Hebei Province, China. The storage roots from cultivars such as Yizi 138 and Beijing 553 developed lesions on their surface during storage. Typical lesions consisted of alternating light and dark brown concentric rings that were darker than the root surface. The size of the lesions was 49 × 63 mm (11 to 75 × 36 to 80 mm, n = 20) on average. The lesion spot was slightly concave. Cutting the diseased roots revealed the lesions could extend into the center of the roots, often with cavities. It smelled bitter within the necrotic tissues and was dark brown or black. The disease incidence was about 10 to 20%. A Fusarium species was consistently isolated from the diseased roots (n = 20). Mycelial plugs from a pure culture of the pathogen on potato dextrose agar were placed on the surface of disinfected sweet potato roots incubated at 25°C with 80 to 90% relative humidity and uninoculated roots were used as control. The same symptom was observed after 14 days on all roots (n = 20) inoculated with the pathogen. The same Fusarium species was consistently reisolated from all lesions. The pathogen was cultured on carnation leaf agar (CLA) for 10 days at 25°C with a 12-h photoperiod. The fungus produced two types of spores on CLA: microconidia were thin-walled, hyaline, fusiform to ovoid, generally 1- or 2-celled, and 3.1 to 9.4 × 1.3 to 2.9 μm (n = 20); macroconidia were slightly curved with blunt and rounded apical cell and notched basal cells, mostly 4- to 8-celled, and 13.3 to 36.5 × 2.3 to 3.8 μm (n = 40). On the basis of morphological characteristics, the fungal isolates were identified as Fusarium solani (Mart.) Appel & Wollenw. emend. Snyd. & Hans. (1). The genomic DNA of the pathogen cultured in potato dextrose broth for 3 days at 25°C was extracted with the CTAB method. The ITS-rDNA sequence, a fragment of the translation elongation factor 1-alpha (EF-1α) gene sequence, and the beta tubulin gene sequence was amplified using the paired primers ITS1F/ITS4(CTTGGTCATTTAGAGGAAGTAA/TCCTCCGCTTATTGA TATGC), EF-1/EF-2 (ATGGGTAAGGARGACAAGAC/GGARGTACCAGTSATCATGTT) and Bt-1/Bt-2(AACATGCGTGAGATTGTAAGT/TCTGGATGTTGTTGGGAATCC), respectively. Those sequence showed 97% homology with ITS sequence of F. solani (GenBank Accession No. AF178407), 99% homology with EF-1α sequence of F. solani (JX945169, DQ247593, and DQ247354), and 98% homology with beta tubulin gene sequence of F. solani (AB553621), respectively. The new sequences of ITS-rDNA, EF-1α, and beta tubulin were deposited in GenBank (KF255997, KF255995, and KF255996). The pathogen was identified as F. solani based on its morphological and molecular characteristics. To our knowledge, this is the first report of F. solani-induced fusarium root rot and stem canker on sweet potato storage roots in China. A rootlet root rot attributed to F. solani in China was reported previously (2). References: (1) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual, Blackwell Publishing, Ames, IA, 2006. (2) Q. J. Liu et al. Acta Phytopathol. Sin. 12(3):21,1982.
中国是世界上最大的甘薯（Ipomoea batatas (L.) Lam）生产国，其年产量约为1亿吨。2011年至2013年在中国河北省开展了甘薯贮藏期病害调查。贮藏期的冀紫138和北京553等品种的贮藏根表面出现病斑。典型病斑由深浅交替的同心环组成，颜色比根表面深。病斑大小平均为49×63毫米（11至75×36至80毫米，n = 20）。病斑处稍有凹陷。切开患病根后发现病斑可延伸至根的中心，常有空洞。坏死组织内有苦味，呈深褐色或黑色。发病率约为10%至20%。从患病根（n = 20）中始终能分离出一种镰刀菌。将病原菌在马铃薯葡萄糖琼脂上的纯培养菌丝块接种于经消毒的甘薯根表面，置于25°C、相对湿度80%至90%的环境中培养，未接种的根作为对照。接种病原菌14天后，所有接种根（n = 20）均出现相同症状。从所有病斑中始终能再次分离出相同的镰刀菌。病原菌在香石竹叶琼脂（CLA）上于25°C、12小时光周期条件下培养10天。该真菌在CLA上产生两种类型的孢子：小型分生孢子薄壁、透明、梭形至卵形，通常为1或2细胞，大小为3.1至9.4×1.3至2.9微米（n = 20）；大型分生孢子稍弯曲，顶端细胞钝圆，基部细胞有缺刻，大多为4至8细胞，大小为13.3至36.5×2.3至3.8微米（n = 40）。根据形态特征，将该真菌分离物鉴定为茄病镰刀菌（Fusarium solani (Mart.) Appel & Wollenw. emend. Snyd. & Hans.）（1）。将在马铃薯葡萄糖肉汤中于25°C培养3天的病原菌基因组DNA用CTAB法提取。分别使用引物ITS1F/ITS4（CTTGGTCATTTAGAGGAAGTAA/TCCTCCGCTTATTGATATGC）、EF-1/EF-2（ATGGGTAAGGARGACAAGAC/GGARGTACCAGTSATCATGTT）和Bt-1/Bt-2（AACATGCGTGAGATTGTAAGT/TCTGGATGTTGTTGGGAATCC）扩增ITS-rDNA序列、翻译延伸因子1-α（EF-1α）基因序列片段和β微管蛋白基因序列。这些序列与茄病镰刀菌的ITS序列（GenBank登录号AF178407）同源性为97%，与茄病镰刀菌的EF-1α序列（JX945169、DQ247593和DQ247354）同源性为99%，与茄病镰刀菌的β微管蛋白基因序列（AB553621）同源性为98%。ITS-rDNA、EF-1α和β微管蛋白的新序列已存入GenBank（KF255997、KF255995和KF255996）。根据其形态和分子特征，该病原菌被鉴定为茄病镰刀菌。据我们所知，这是中国关于茄病镰刀菌引起甘薯贮藏根镰刀菌根腐和茎溃疡病的首次报道。此前曾报道过中国一种由茄病镰刀菌引起的细根根腐病（2）。参考文献：（1）J. F. Leslie和B. A. Summerell。《镰刀菌实验室手册》，Blackwell出版社，艾姆斯，爱荷华州，2006年。（2）刘全吉等。《植物病理学报》12(3):21，1982年。
