Niblack T L, Wrather J A, Heinz R D, Donald P A
Professor, Department of Crop Sciences, University of Illinois, Urbana 61801.
Professor, Department of Plant Microbiology and Plant Pathology, University of Missouri Delta Center, Portageville 63873.
Plant Dis. 2003 Aug;87(8):929-932. doi: 10.1094/PDIS.2003.87.8.929.
The soybean cyst nematode, Heterodera glycines, is the most economically important pathogen of soybean in Missouri. Knowledge of the nematode's distribution and ability to adapt to resistant varieties is important for determining crop losses and establishing research priorities. No previous surveys of Missouri have provided reliable population density and phenotypic diversity data; therefore, we conducted a random survey to obtain both. Two samples from each of 200 fields were collected; 392 samples were processed for extractions of cysts and eggs. Two hundred and forty seven (63%) of the samples had detectable cyst nematode populations, which ranged from 15 to 149,700 eggs per 250 cm of soil. The lowest average population densities were observed in the east-central region of Missouri (2,260 eggs per 250 cm of soil), and the highest were observed in the northeast (9,238 eggs per 250 cm of soil), but among the eight regions sampled, mean population densities did not differ significantly. These population densities were potentially responsible for losses worth over $58 million in 1999 in Missouri. Race tests were conducted on populations from 183 samples. In order of frequency, races 3, 1, and 2 accounted for 86% of H. glycines populations. Nearly 60% of the populations were virulent (able to produce females) on plant introduction (PI) 88788, which is the source of resistance for most H. glycines-resistant cultivars. More than a third of the populations were virulent on cv. Peking, another common resistance source. Very few populations were virulent on PI 90763 or PI 437654, suggesting that these sources of resistance should be exploited more frequently.
大豆胞囊线虫（Heterodera glycines）是密苏里州大豆最具经济重要性的病原体。了解该线虫的分布及其适应抗性品种的能力对于确定作物损失和确立研究重点至关重要。此前尚无针对密苏里州的调查提供可靠的种群密度和表型多样性数据；因此，我们进行了一次随机调查以获取这两方面的数据。从200个田地中各采集了两个样本；对392个样本进行了处理以提取胞囊和卵。其中247个（63%）样本检测到有胞囊线虫种群，每250厘米土壤中的卵数在15至149,700个之间。在密苏里州中东部地区观察到的平均种群密度最低（每250厘米土壤中有2260个卵），而在东北部最高（每250厘米土壤中有9238个卵），但在采样的八个区域中，平均种群密度差异不显著。这些种群密度在1999年可能导致密苏里州损失超过5800万美元。对来自183个样本的种群进行了生理小种测试。按出现频率排序，生理小种3、1和2占大豆胞囊线虫种群的86%。近60%的种群对植物引进品种（PI）88788具有毒性（能够产生雌虫），PI 88788是大多数抗大豆胞囊线虫品种的抗性来源。超过三分之一的种群对品种北京也具有毒性，北京是另一种常见的抗性来源。极少种群对PI 90763或PI 437654具有毒性，这表明应更频繁地利用这些抗性来源。
