Lu X, Robertson A E, Byamukama E Z, Nutter F W
Department of Plant Pathology, Iowa State University, Ames 50011.
Plant Dis. 2010 Feb;94(2):167-173. doi: 10.1094/PDIS-94-2-0167.
The relative importance of stem canker of soybean in Iowa compared with other soybean diseases present in the state was assessed using data collected from over 3,400 soybean fields sampled in the Iowa Soybean Disease Survey that was conducted from 2005 to 2007. Symptomatic plant tissues from soybean plants with stem canker symptoms were cultured on acidified potato dextrose agar. The prevalence of stem canker on soybean in 2005 in Iowa was 2.6%; the disease was not detected in 2006 and 2007. In 2005, 63 isolates with Diaporthe/Phomopsis characteristics were collected. To identify isolates to fungal species and variety, single-spored isolates were subjected to polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and sequencing of the internal transcribed spacer (ITS) region. Fourteen isolates were identified as D. phaseolorum var. caulivora (northern stem canker) and 49 as Phomopsis longicolla. To quantify and compare the aggressiveness of D. phaseolorum var. caulivora isolates collected in Iowa, nine isolates were arbitrarily selected for components analysis. Incubation period, rate of lesion expansion, final lesion length, and time to plant death for each isolate were quantified. Significant differences in components of aggressiveness were detected among the nine isolates. Results from this work suggest stem canker is a minor disease of soybean in Iowa.
利用2005年至2007年爱荷华州大豆病害调查中从3400多个大豆田采集的数据，评估了大豆茎溃疡病在爱荷华州相对于该州存在的其他大豆病害的相对重要性。对有茎溃疡症状的大豆植株的有症状植物组织在酸化马铃薯葡萄糖琼脂上进行培养。2005年爱荷华州大豆上茎溃疡病的发病率为2.6%；2006年和2007年未检测到该病。2005年，收集到63个具有拟茎点霉/茎点霉特征的分离株。为了将分离株鉴定到真菌物种和变种，对单孢分离株进行聚合酶链反应-限制性片段长度多态性（PCR-RFLP）分析和内部转录间隔区（ITS）测序。14个分离株被鉴定为菜豆壳球孢变种（北方茎溃疡病菌），49个为菜豆茎点霉。为了量化和比较在爱荷华州收集的菜豆壳球孢变种分离株的致病力，随机选择9个分离株进行成分分析。对每个分离株的潜伏期、病斑扩展速率、最终病斑长度和植株死亡时间进行了量化。在这9个分离株中检测到致病力成分的显著差异。这项工作的结果表明，茎溃疡病在爱荷华州是大豆的一种次要病害。
