ABSTRACT
A quantitative trait locus (QTL) is a genetic locus that affects a quantitative trait. The development of molecular markers and the subsequent constructions of molecular linkage maps enabled scientists to identify and to map a large number of QTLs in soybean. The first study of associative mapping of QTLs in soybean was based on the original soybean molecular linkage map (Keim et al. 1990a, b). From 1990 to 2007, over 270 papers (excluding reviews) on QTL mapping studies in soybean were published. Figure 5-1 shows the annual publications collected in the “Biological Abstracts” database (Thomson Scientific, Inc., 2008) on QTL mapping studies
1Department of Crop and Soil Sciences, Michigan State University, A384E Plant & Soil Sciences Building, East Lansing, MI 48824-1325, USA. 2USDA-ARS, Department of Agronomy, Iowa State University, Ames, IA 50011, USA. *Corresponding author: wangdech@msu.edu
in soybean. The first big increase in the number of publications occurred in 1996, six years after the publication of the first molecular linkage map in soybean. The second large increase in the number of publications occurred in 2004, five years after the publication of an integrated soybean linkage map with a large number of user-friendly markers, mainly simple sequence repeat (SSR) markers (Cregan et al. 1999). The number of publications on QTL mapping studies in soybean ranged from 27 to 39 per year in the past four years. The number is expected to increase in the next five years due to the addition of more user-friendly and high-throughput markers to the integrated soybean map (Song et al. 2004; Choi et al. 2007).
