Pataky J K, du Toit L J, Revilla P, Tracy W F
Department of Crop Sciences, University of Illinois, Urbana 61801.
Department of Agronomy, University of Wisconsin, Madison 53706.
Plant Dis. 1998 Aug;82(8):939-944. doi: 10.1094/PDIS.1998.82.8.939.
Over 800 open-pollinated (OP) varieties of sweet corn were grown and named in the century prior to the development of hybrids, but only a few of the historically important OP cultivars exist today. Alleles that could improve disease resistance of modern sweet corn may be present in the OP cultivars still in existence. The objectives of this research were to compare 36 OP sweet corn cultivars to modern commercial hybrids for reactions to Stewart's wilt, common rust, northern leaf blight (NLB), and southern leaf blight (SLB), and to classify the OP cultivars based on phenotypic reactions to these four diseases. Plants were inoculated in 1994, 1995, and 1996 with Erwinia stewartii, Puccinia sorghi, Exserohilum turcicum, or Bipolaris maydis. Symptoms were rated on a whole-plot basis, and ratings were analyzed by analysis of variance (ANOVA). Means were separated by Bayesian least significant difference values. Some of the OP cultivars had phenotypes that were intermediate to moderately resistant to Stewart's wilt, common rust, NLB, or SLB, but none of the cultivars were more resistant than the best commercial hybrids. Distributions of ratings for rust, NLB, and SLB were less disperse for the OP cultivars than for commercial hybrids. Hence, the resistance of modern sweet corn germ plasm to Stewart's wilt, rust, and NLB appears to be greater than that of the OP cultivars. OP cultivars and four standard hybrids were placed into groups based on a hierarchical cluster analysis of disease reactions. The seven groups formed from the cluster analysis of disease ratings were considerably different than those formed from isozyme variation and morphological characteristics. The partial resistance of some cultivars, e.g., Golden Sunshine, Country Gentleman, Stowell's Evergreen, and Red, may be relatively diverse since these cultivars were placed in different groups based on isozyme and morphological variation. OP cultivars with moderate levels of resistance may be sources of resistance alleles not present in commercial hybrids.
在杂交种培育之前的那个世纪，人们种植并命名了800多个甜玉米开放授粉（OP）品种，但如今仅存少数具有历史重要性的OP栽培品种。现存的OP栽培品种中可能存在能够提高现代甜玉米抗病性的等位基因。本研究的目的是比较36个OP甜玉米品种与现代商业杂交种对斯图尔特枯萎病、普通锈病、北方叶斑病（NLB）和南方叶斑病（SLB）的反应，并根据对这四种病害的表型反应对OP品种进行分类。1994年、1995年和1996年，用斯图尔特欧文氏菌、高粱柄锈菌、大斑凸脐蠕孢或玉蜀黍平脐蠕孢对植株进行接种。在全田基础上对症状进行评级，并通过方差分析（ANOVA）对评级进行分析。均值通过贝叶斯最小显著差值进行分离。一些OP品种对斯图尔特枯萎病、普通锈病、NLB或SLB的表型为中等抗性，但没有一个品种比最好的商业杂交种更抗病。OP品种锈病、NLB和SLB评级的分布比商业杂交种的分布更集中。因此，现代甜玉米种质对斯图尔特枯萎病、锈病和NLB的抗性似乎比OP品种更强。基于病害反应的层次聚类分析，将OP品种和四个标准杂交种分为不同的组。由病害评级聚类分析形成的七组与由同工酶变异和形态特征形成的组有很大不同。一些品种，如金色阳光、乡村绅士、斯托韦尔常绿和红色，其部分抗性可能相对多样，因为根据同工酶和形态变异，这些品种被分在了不同的组中。具有中等抗性水平的OP品种可能是商业杂交种中不存在的抗性等位基因的来源。
