Rivera V, Rengifo J, Khan M, Geiser D M, Mansfield M, Secor G
Department of Plant Pathology, North Dakota State University, Fargo.
Fusarium Research Center, Department of Plant Pathology, Pennsylvania State University, University Park.
Plant Dis. 2008 Nov;92(11):1589. doi: 10.1094/PDIS-92-11-1589B.
In the United States, yellows disease of sugar beet (Beta vulgaris), which causes wilt, early death, and yield reduction, is caused primarily by Fusarium oxysporum f. sp. betae (3,4), but F. graminearum (2) has also been implicated. During the past 3 years, a similar disease causing yellowing and severe decline appeared in some sugar beet fields of central and southwest Minnesota planted with cultivars resistant to yellows. The disease has become a concern to the local sugar beet industry, which produces 56% of sugar beets in the United States. From 2005 to 2007, isolations were made from sugar beets collected in commercial fields and from a Fusarium screening nursery showing symptoms of yellowing, interveinal chlorosis, scorching, stunting, vascular discoloration of the taproot, and early death of plants. Of 96 Fusarium isolates recovered and used in root-dip inoculation trials in the greenhouse, 58 were pathogenic to sugar beets. On the basis of morphology, 12 were identified as F. oxysporum, 6 as F. graminearum, and 40 as a novel Fusarium species. The remaining 38 isolates were nonpathogenic. All three pathogenic Fusarium species were isolated from taproots, but only the novel Fusarium was isolated from petioles. In culture, the novel Fusarium exhibited a bright orange color on the underside of potato dextrose agar medium and produced micro- and macroconidia sparsely. Hyphal tip isolates of all novel Fusarium isolates were pathogenic, causing typical yellowing symptoms and plant death to the Fusarium yellows susceptible sugar beet cv. VDH46177 in replicated greenhouse trials. Isolates were successfully reisolated from the symptomatic plants, fulfilling Koch's postulates. Restriction fragment length polymorphism (RFLP) endonuclease digestion patterns (Alu1, Fnu4HI, HaeIII, and HhaI) of the internal transcribed spacer (ITS) region of 40 pathogenic novel isolates showed a distinct pattern compared with known Fusarium species. Thin layer chromatography analysis of 13 novel isolates detected the type A trichothecenes neosolaniol and 4,15-diacetoxyscirpenol. Partial sequences of the translation elongation factor 1-α (TEF) from 12 single-spored novel Fusarium isolates were generated. BLAST analysis of the TEF sequence against the FUSARIUM-ID (1) and GenBank databases did not match any known Fusarium species. On the basis of pathogenicity, morphology, RFLP patterns, mycotoxin production, and TEF sequence analysis it appears that this is a new species of Fusarium, but additional multilocus phylogenetic analyses are warranted. The natural occurrence of this novel Fusarium pathogen in sugar beet may have implications in breeding for resistance to Fusarium yellows, since yellow decline has been observed in purportedly Fusarium-tolerant cultivars in the Minnesota and North Dakota production regions. References: (1) D. M. Geiser et al. Eur. J. Plant Pathol. 110:473, 2004. (2) L. E. Hanson. Plant Dis. 90:686, 2006. (3). L. E. Hanson. Plant Dis. 90:1554, 2006. (4) C. E. Windels et al. Plant Dis. 89:341, 2005.
在美国，甜菜黄化病（由甜菜（Beta vulgaris）引起）会导致枯萎、过早死亡和产量下降，该病主要由尖孢镰刀菌甜菜专化型（Fusarium oxysporum f. sp. betae）引起（3,4），但禾谷镰刀菌（F. graminearum）（2）也与之有关。在过去3年中，在明尼苏达州中部和西南部一些种植了抗黄化病品种的甜菜田出现了一种类似的导致叶片发黄和严重衰退的病害。这种病害已引起当地甜菜产业的关注，该地区生产美国56%的甜菜。2005年至2007年期间，从商业田采集的甜菜以及一个显示叶片发黄、脉间失绿、焦枯、生长受阻、主根维管束变色和植株过早死亡症状的镰刀菌筛选苗圃中采集的甜菜上进行了分离。在温室中回收并用于浸根接种试验的96株镰刀菌分离物中，58株对甜菜具有致病性。根据形态学，12株被鉴定为尖孢镰刀菌，6株为禾谷镰刀菌，40株为一种新的镰刀菌物种。其余38株分离物无致病性。所有三种致病镰刀菌物种均从主根中分离得到，但只有新的镰刀菌从叶柄中分离得到。在培养物中，新的镰刀菌在马铃薯葡萄糖琼脂培养基底部呈现亮橙色，产孢稀疏，产生小型和大型分生孢子。在重复的温室试验中，所有新镰刀菌分离物的菌丝尖端分离物均具有致病性，可导致对镰刀菌黄化病敏感的甜菜品种VDH46177出现典型的黄化症状和植株死亡。从有症状的植株上成功重新分离出分离物，满足柯赫氏法则。40株致病新分离物的内部转录间隔区（ITS）的限制性片段长度多态性（RFLP）内切酶消化模式（Alu1、Fnu4HI、HaeIII和HhaI）与已知镰刀菌物种相比呈现出独特的模式。对13株新分离物的薄层色谱分析检测到A型单端孢霉烯族毒素新茄病镰刀菌烯醇和4,15 - 二乙酰氧基雪腐镰刀菌烯醇。从12株单孢新镰刀菌分离物中获得了翻译延伸因子1 - α（TEF）的部分序列。将TEF序列与FUSARIUM - ID（1）和GenBank数据库进行BLAST分析，未与任何已知镰刀菌物种匹配。基于致病性、形态学、RFLP模式、霉菌毒素产生和TEF序列分析，似乎这是一种新的镰刀菌物种，但需要进行更多的多位点系统发育分析。这种新的镰刀菌病原体在甜菜中的自然发生可能对镰刀菌黄化病抗性育种有影响，因为在明尼苏达州和北达科他州产区据称为耐镰刀菌的品种中已观察到黄化衰退现象。参考文献：（1）D. M. Geiser等人，《欧洲植物病理学杂志》110:473，2004年。（2）L. E. Hanson，《植物病害》90:686，2006年。（3）L. E. Hanson，《植物病害》90:1554，2006年。（4）C. E. Windels等人，《植物病害》89:341，2005年。
