Assisted Breeding in Sugar Beets

Molecular insight and methods applied to plant breeding and germplasm enhancement is the goal of assisted breeding, also known as marker assisted breeding, marker assisted selection, molecular plant breeding, or genome-wide selection, among others. The basic idea is that most, if not all, heritable components of agronomic performance can be assayed with an unbiased, uniform, and comparatively inexpensive set of measures that are highly or completely correlated with phenotypic values. Typically such heritable components are genetically controlled, thus the panoply of DNA-based correlative methods should provide the requisite tools for assisted breeding to be successful. Whether DNA-based methods are successful in predicting agronomic performance depends on a host of considerations, many of which remain to be completely addressed for sugar beet, and thus assisted breeding remains somewhat empirical in practice, at least with respect to the specific traits of interest. Most sugar beet breeding and improvement programs have initiated assisted breeding efforts, primarily as a first step to discover marker associations with traits. These initial activities serve a number of important functions such as determining the complexity of trait inheritance, narrowing the possible range of genes and loci involved in phenotypic expression in different populations, and following the progress of sugar beet improvement following hybridization with wild and unadapted germplasm. It is unlikely that breeding will or should ever rely completely on assisted methods, however selection of the most promising germplasm can be greatly accelerated using molecular insights and knowledge.