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Abbreviations: IT, information technology; MARS, marker assisted recurrent selection; MTI, multiple trait index; PCR, polymerase chain reaction; QC, quality control; QTL, quantitative trait loci; RFLP, restriction fragment length polymorphisms; SNP, single nucleotide polymorphism; SSR, simple sequence repeat; TDT, transmission disequilibrium test.
In the 1980s, DNA-based molecular markers were identified as having the potential to enhance corn (Zea mays L.) breeding. Research has demonstrated the advantage of using molecular markers for selection of simply inherited traits, however only a few studies have evaluated the potential to enhance genetic gain for quantitative traits. In the late 1990s, Monsanto decided to implement marker assisted selection for quantitative traits in our global plant breeding programs. We built genotyping systems and information tools and developed marker assisted methodologies that increased the mean performance in elite breeding populations.
DNA-based molecular markers were identified as having potential utility in corn breeding in the 1980s (Helentjaris et al., 1985; Paterson et al., 1988). The identification of restriction fragment length polymorphisms (RFLPs) (Botstein et al, 1980) created a new research discipline typically referred to as molecular breeding. The central dogma of molecular breeding involves the utilization of molecular marker fingerprints to improve selection efficiency in plant breeding programs.
Scientists have researched applications such as the characterization of genetic variation, molecular marker assisted backcrossing, quantitative trait mapping, and molecular marker assisted selection (Charcosset and GaIlais, 2003; de Vienne and Causse, 2003; Hoisington and Melchinger, 2004; Frisch, 2004; Mohler and Singrun, 2004). Numerous quantitative trait loci (QTL) mapping studies have been published on a wide range of phenotypic traits (Lawrence et al., 2004, 2005, 2007). However, after 20 years of research there are a limited number of publications demonstrating results in plant breeding programs.
This article focuses on the application of molecular marker technologies to Monsanto's plant breeding programs with emphasis on selecting for quantitative traits.
The goals of this article are to
* define the major components needed to implement large-scale molecular marker assisted breeding methodologies;
* outline the structural changes in Monsanto's breeding programs to accommodate each of these components;
* provide empirical results from molecular marker assisted breeding methodologies for quantitative traits;
* outline one of Monsanto's methods to improve the precision in estimating QTL genetic locations and account for population...