1 Applications of Genomics Technologies to Enhance Rate of Genetic Progress

The commercial grain yield of maize in the U.S. Corn Belt has undergone significant genetic improvement since the initiation of hybrid breeding in the first half of the 20th Century. Designing effective molecular enhanced breeding strategies that improve on the outcomes of the conventional pedigree breeding strategies is a challenge for commercial maize improvement programs today. Most of the traits of importance to the breeder are genetically complex and quantitative in nature. Genetically mapping these traits in elite breeding populations is difficult. Conventional mapping approaches in structured populations are often not relevant to the elite crosses of a maize breeder, are time consuming to create and even when successful usually only offer low levels of mapping resolution (ca. 10 to 20 cM). Therefore, considerable interest has emerged in the use of alternative methods for the mapping of quantitative traits. Genetic association mapping methods have been the subject of great interest in human genetics. More recently genetic association studies have been performed in crop plants, with some promising results. Much work still remains to develop association mapping methodology that is applicable to properties, such as pedigree relationships, among the elite populations of a maize breeder. We will discuss the utility of these approaches for mapping complex traits and issues for consideration in their application to breeding. Media Summary New methods of mapping offer a promising route to the identification of genetic markers for the genes of complex traits and provide a foundation for molecular enhanced breeding of maize