Molecular markers - where are we today?
2001
Kraft, T. (Syngenta, Landstkrona (Sweden))
A molecular marker can represent any piece of DNA that can easily be scored using different molecular techniques. By studying the offspring from controlled crosses, the inheritance of both markers and phenotypic traits can be determined. When a marker is located close to a gene, we will detect an association between marker genotypes and phenotypic trait values among the offspring. We can then use the marker to select plants with the desired genotype, thereby circumventing the need of phenotypic evaluations. Marker genotyping can be done at a very early stage, thus saving a lot of time, and is often both cheaper and more accurate than phenotypic evaluations. During the last decade, markers have been used in sugar beet breeding to alter some important traits with a simple inheritance, such as Rhizomania resistance. Today, a lot of effort is spent on using molecular markers to dissect more complex traits that are influenced by many genes and by the environment. The next step is to use this information in the creation of resistant varieties. Another development that is taking place right now is to study the genes themselves instead of working with associations between markers and phenotypes. By sequencing the whole sugar beet genome we can detect all genes. Much work remains then on understanding the function of the genes and how they interact with each other and with the environment. The goal is of course to alter the genes directly instead of using markers associated with the genes.
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