ARS | Publication request: Observations from a quarter century of evaluating reactions of sweet corn hybrids in disease nurseries

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 31, 2011
Publication Date: December 2, 2011
Citation: Pataky, J.K., Williams, M., Headrick, M.M., Nankam, C., Du Toit, L., Michener, P.M. 2011. Observations from a quarter century of evaluating reactions of sweet corn hybrids in disease nurseries. Plant Disease. 95:1492-1506.

Interpretive Summary: Since 1984, nearly 3,700 commercial or pre-commercial sweet corn hybrids have been evaluated for reactions to common rust, northern corn leaf blight, Stewart’s wilt, southern corn leaf blight, and maize dwarf mosaic in nurseries at the University of Illinois (UI). In certain years, hybrids also were evaluated for reactions to southern rust, anthracnose leaf blight, gray leaf spot, and Goss’s wilt. This article summarizes the trends observed in disease resistance over a 27- year period. In addition, an 8-year study of hybrid response to selected P450-metabolized herbicides is summarized. Key observations include 1) the half-life of information from any annual UI disease nursery appears to be slightly more than 5 years, 2) the percentage of hybrids with the three major endosperm types has shifted largely away from the su1 allele to the sh2 allele, 3) possibly the greatest change in disease reactions of sweet corn hybrids in the past quarter century has been the widespread use of Rp genes to control Puccinia sorghi, and 4) fewer than 25 hybrids are homozygous for mutant cytochrome P450 alleles (i.e. herbicide sensitive) but 20% or more of the hybrids evaluated in the nursery since 2002 have intermediate responses indicative of heterozygous cytochrome P450 genotypes. While disease resistance is a necessary trait for hybrids in some markets, resistance by itself will not sell a hybrid. In order for hybrids to be widely grown, several essential horticultural quality and agronomic traits are of greater importance than disease resistance.

Technical Abstract: Sweet corn is one of the most popular vegetable crops in North America due in part to significant improvements made in eating quality in the last quarter century. Several plant diseases are major threats to sweet corn production. While resistance genes exist for many of these diseases, incorporating disease resistance genes into sweet corn without reducing eating quality can be difficult. As a result, the 500 to 600 sweet corn hybrids available for sale each year have a wide range of reactions to several diseases that may be important in some, but not all, of the major market segments. This article summarizes observations made in the University of Illinois sweet corn disease nursery for the period of 1984-2010. This work documents the impact of 1) advances in methodology used to quantify disease reactions, 2) integration of disease resistance genes into sweet corn, and 3) frequency of alleles conditioning sensitivity to P450-metabolized herbicides.