ARS | Publication request: QUANTITATIVE TRAIT LOCI AND METABOLIC PATHWAYS

Submitted to: Proceedings of the National Academy of Sciences
Publication Type: Proceedings
Publication Acceptance Date: June 2, 1997
Publication Date: N/A

Interpretive Summary: The past decade has seen an explosion of information on the structure, organization, and functions of the corn genome, including the development of high-density genetic maps. One application of new technologies has been the genetic dissection of agronomic traits with much greater precision than was previously possible. However for most traits, genetic and biochemical information on biochemical pathways is still extremely limited, and therefore, it is difficult go from these studies to strategies for crop improvement. Our goal in this research project is to analyze the genetic control of an economically important trait (resistance to the corn earworm) and to interpret the results in terms of the well-characterized biochemical pathway. The results of our studies demonstrate the importance on trait expression of: 1) a class of genes called "regulatory," 2) interconnecting pathways, and 3) independent control of synthesis of similar chemical compounds. These studies give novel insight into genetic control of trait expression that is applicable to a broad range of plant breeding problems allowing researchers to make better predictions of the appropriate genes to alter for crop improvement.

Technical 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 in a pathway or the nature of their interaction with other loci are generally not possible. An exception is resistance to the corn earworm (CEW), Helicoverpa zea (Boddie), in maize (Zea mays L.) due to 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: 1) the importance of regulatory loci as QTLs, 2) the importance of interconnecting biochemical pathways on product levels, 3) evidence for "channeling" of intermediates, allowing independent synthesis of related compounds, 4) the utility of QTL analysis in clarifying the role of specific genes in a biochemical pathway, and 5) identification of a previously unknown locus on chromosome 9S affecting flavone level. A greater understanding of the genetic basis of maysin synthesis and associated CEW resistance will lead to improved breeding stategies. 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.