Quantitative trait loci and metabolic pathways

Quantitative trait loci and metabolic pathways

^*Plant Genetics Research Unit, Agricultural Research Service-United States Department of Agriculture, Columbia, MO 65211; ^†Plant Science Unit, University of Missouri, Columbia, MO 65211; ^§Richard B. Russell Research Center, University of Georgia, Athens, GA 30613; and ^¶Insect Biology and Population Research Laboratory, Agricultural Research Service-United States Department of Agriculture, Tifton, GA 31793

Abstract

The interpretation of quantitative trait locus (QTL) studies is limited by the lack of information on metabolic pathways leading to most economic traits. Inferences about the roles of the underlying genes with a pathway or the nature of their interaction with other loci are generally not possible. An exception is resistance to the corn earworm Helicoverpa zea (Boddie) in maize (Zea mays L.) because of maysin, a C-glycosyl flavone synthesized in silks via a branch of the well characterized flavonoid pathway. Our results using flavone synthesis as a model QTL system indicate: (i) the importance of regulatory loci as QTLs, (ii) the importance of interconnecting biochemical pathways on product levels, (iii) evidence for “channeling” of intermediates, allowing independent synthesis of related compounds, (iv) the utility of QTL analysis in clarifying the role of specific genes in a biochemical pathway, and (v) identification of a previously unknown locus on chromosome 9S affecting flavone level. A greater understanding of the genetic basis of maysin synthesis and associated corn earworm resistance should lead to improved breeding strategies. More broadly, the insights gained in relating a defined genetic and biochemical pathway affecting a quantitative trait should enhance interpretation of the biological basis of variation for other quantitative traits.

Footnotes

↵ ‡ To whom reprint requests should be addressed. e-mail: mcmullen{at}teosinte.agron.missouri.edu.
This paper was presented at a colloquium entitled “Protecting Our Food Supply: The Value of Plant Genome Initiatives,” organized by Michael Freeling and Ronald L. Phillips, held June 2–5, 1997, sponsored by the National Academy of Sciences at the Arnold and Mabel Beckman Center in Irvine, CA.
ABBREVIATIONS:

QTL,

quantitative trait locus;

CEW,

corn earworm;

RFLP,

restriction fragment length polymorphism