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Observations from a Quarter Century of Evaluating Reactions of Sweet Corn Hybrids in Disease Nurseries

Host resistance is one of the most effective and efficient ways to control plant diseases. Resistance eliminates or minimizes losses from diseases and reduces the need for other control tactics. Resistance also can be integrated easily with other pest management practices. Resistance and susceptibility are two extremes of a continuum of host reactions to diseases. Resistance is a measure of the ability of the host to reduce the growth, reproduction, and/or disease-producing abilities of the pathogen, thus resulting in less severe disease symptoms. Major genes for resistance, such as the Rp1-D, Ht1, or Mdm1 genes in maize, can prevent or substantially limit disease development if specific virulence (i.e., races) occurs infrequently in pathogen populations. Consequently, cultivars with major gene resistance usually have clearly distinguishable phenotypes. Major gene resistance may become ineffective if specific, complementary virulence becomes prevalent in the pathogen. Since 1984, nearly 3,700 commercial or pre-commercial sweet corn hybrids were evaluated for disease reactions in nurseries at the University of Illinois. Each year, hybrids were evaluated for reactions to four diseases that consistently were prevalent on sweet corn grown in North America. This article presents a summary of observations and trends from more than a quarter century of evaluating sweet corn hybrids in University of Illinois disease nurseries.