Genetics, Vol. 149, 1997-2006, August 1998, Copyright © 1998

Genetic Mechanisms Underlying Apimaysin and Maysin Synthesis and Corn Earworm Antibiosis in Maize (Zea mays L.)

E. A. Leea, P. F. Byrneb, M. D. McMullena,c, M. E. Snookd, B. R. Wisemane, N. W. Widstrome, and E. H. Coea,c
a Plant Genetics Research Unit, Agricultural Research Service, U.S. Department of Agriculture, Columbia, Missouri 65211
b Department of Soil and Crop Sciences, Colorado State University, Fort Collins, Colorado 80523
c Department of Agronomy, Plant Sciences Unit, University of Missouri, Columbia, Missouri 65211
d Phytochemical Research Unit, Agricultural Research Service, U.S. Department of Agriculture, Athens, Georgia 30613
e Insect Biology and Population Management Research Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Tifton, Georgia 31793

Corresponding author: M. D. McMullen, 301 Curtis Hall, University of Missouri, Columbia, MO 65211., mcmullen{at}teosinte.agron.missouri.edu (E-mail).

Communicating editor: J. CHORY

C-glycosyl flavones in maize silks confer resistance (i.e., antibiosis) to corn earworm (Helicoverpa zea [Boddie]) larvae and are distinguished by their B-ring substitutions, with maysin and apimaysin being the di- and monohydroxy B-ring forms, respectively. Herein, we examine the genetic mechanisms underlying the synthesis of maysin and apimaysin and the corresponding effects on corn earworm larval growth. Using an F2 population, we found a quantitative trait locus (QTL), rem1, which accounted for 55.3% of the phenotypic variance for maysin, and a QTL, pr1, which explained 64.7% of the phenotypic variance for apimaysin. The maysin QTL did not affect apimaysin synthesis, and the apimaysin QTL did not affect maysin synthesis, suggesting that the synthesis of these closely related compounds occurs independently. The two QTLs, rem1 and pr1, were involved in a significant epistatic interaction for total flavones, suggesting that a ceiling exists governing the total possible amount of C-glycosyl flavone. The maysin and apimaysin QTLs were significant QTLs for corn earworm antibiosis, accounting for 14.1% (rem1) and 14.7% (pr1) of the phenotypic variation. An additional QTL, represented by umc85 on the short arm of chromosome 6, affected antibiosis (R2 = 15.2%), but did not affect the synthesis of the C-glycosyl flavones.




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