ABSTRACT

The number of published studies concerning the mapping of genomic variants associated with quantitative phenotypic variation in maize (as well as many other plant species) has steadily increased over the last 20 years (Fig. 4-1). The rise in mapping studies has been largely attributable to improvements in genotyping (measuring the variation in DNA) associated with increases in the effi ciency and decreases in the cost of DNA marker technologies. Additionally, advances in computer technology and the deployment of user-friendly software have facilitated the more rapid completion of such studies. The maize research community has not reached a steady state for genetic mapping studies, with 42 publications in 2012 after climbing at a rate of nearly two additional publications per year since the advent of molecular marker-based quantitative trait locus (QTL) mapping in 1988. Additional traits and germplasm remain to be genetically investigated; however, the primary strategies employed for the last two decades have reached their inferential limitations. Therefore, the ‘traditional’ QTL linkage mapping procedure has begun to be complemented by newer procedures

Figure 4-1 Number of publications by year for various title keywords including maize 19862012. Shaded area is all publications on maize (left axis); lines from top to bottom represent all breeding articles, all linkage mapping articles and all association mapping articles (right axis). Specifi c title key word searches of Web of Science (Thomson Scientifi c 2013) included: Title=(maize OR Zea); Title=(breeding OR selection) AND Title=(maize OR Zea OR corn) NOT Title=(QTL OR quantitative trait locus OR quantitative trait loci OR QTLs); Title=(QTL OR quantitative trait locus OR quantitative trait loci OR QTLs) AND Title=(maize OR Zea OR corn); Title=(LD OR “linkage disequilibrium” OR GWAS OR “association mapping”) AND Title=(maize OR Zea OR corn).