Elmer Wade H, Covert Sarah F, O'Donnell Kerry
The Connecticut Agricultural Experiment Station, P. O. Box 1106, New Haven 06504.
Warnell School of Forestry and Natural Resources, University of Georgia, Athens 30602.
Plant Dis. 2007 Sep;91(9):1142-1146. doi: 10.1094/PDIS-91-9-1142.
Isolates of two biologically and phylogenetically distinct species, referred to as Fusarium solani f. sp. cucurbitae race 1 (Fsc-1 = Nectria haematococca mating population I [MPI]) and F. solani f. sp. cucurbitae race 2 (Fsc-2 = N. haematococca mating population V [MPV]), were suspected of causing an outbreak of Fusarium foot and fruit rot of pumpkin during 2001 to 2003 in Connecticut, New York, Ohio, and Missouri. Both species affect the fruit, but Fsc-1 also affects the crown and causes a stem rot. In this study, 156 isolates from affected plants and from soil under diseased fruit that tentatively were identified morphologically as members of the F. solani species complex were assayed for pathogenicity on pumpkin seedlings and mature fruit. Results of the pathogenicity assay indicated that 81 of the isolates were Fsc-1. The remaining 74 isolates were either nonpathogenic or only weakly pathogenic on the fruit. A subset of 53 test isolates from soil and plants, plus reference isolates of Fsc-1 and Fsc-2 and an isolate from wheat reported to cause a seedling rot on cucurbits, were characterized phylogenetically by sequencing a portion of the translation elongation factor 1-α gene. A BLAST query of the FUSARIUM-ID database at Pennsylvania State University indicated that 42 of the 53 test isolates were Fsc-1, whereas none were typed as Fsc-2. A polymerase chain reaction assay for mating-type (MAT) idiomorph revealed that all of the Fsc-1 isolates were MAT-1-2, suggesting that the pathogen may be strictly clonal in the affected fields. These findings provide convincing evidence that the Fusarium foot and fruit rot outbreaks were incited by Fsc-1.
两种在生物学和系统发育上不同的物种分离株，分别称为尖孢镰刀菌南瓜专化型1号小种（Fsc - 1 = 血红色丛赤壳交配群体I [MPI]）和尖孢镰刀菌南瓜专化型2号小种（Fsc - 2 = 血红色丛赤壳交配群体V [MPV]），被怀疑在2001年至2003年期间于康涅狄格州、纽约州、俄亥俄州和密苏里州引发了南瓜镰刀菌足腐病和果实腐烂病的爆发。这两个物种都会影响果实，但Fsc - 1还会影响植株顶部并导致茎腐病。在本研究中，对156株从受影响植株以及病果下方土壤中分离得到的菌株进行了检测，这些菌株在形态学上初步被鉴定为茄腐镰刀菌复合种的成员，检测它们对南瓜幼苗和成熟果实的致病性。致病性检测结果表明，其中81株分离株为Fsc - 1。其余74株分离株对果实要么无致病性，要么致病性很弱。从土壤和植株中选取了53株测试分离株的一个子集，加上Fsc - 1和Fsc - 2的参考分离株以及一株据报道能引起葫芦科植物幼苗腐烂病的小麦分离株，通过对翻译延伸因子1 - α基因的一部分进行测序，对它们进行了系统发育特征分析。在宾夕法尼亚州立大学的镰刀菌鉴定数据库中进行BLAST查询表明，53株测试分离株中有42株为Fsc - 1，而没有一株被鉴定为Fsc - 2。一种用于交配型（MAT）特异形态的聚合酶链反应检测表明，所有Fsc - 1分离株均为MAT - 1 - 2，这表明该病原菌在受影响的田块中可能是严格克隆的。这些发现提供了令人信服的证据，表明镰刀菌足腐病和果实腐烂病的爆发是由Fsc - 1引起的。
