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.
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