ARS | Publication request: THEORETICAL EXPECTATIONS FOR THE POTENTIAL USE OF GENETIC MARKERS IN MARKER-ASSISTED SELECTION

Submitted to: Cucurbitaceae Proceedings
Publication Type: Proceedings
Publication Acceptance Date: November 15, 1998
Publication Date: N/A

Interpretive Summary: Selection of plants has traditionally been accomplished visually by the breeder and often the birth of a variety requires 5 to 10 years of testing and evaluation. Any method that would reduce the costs and time of breeding new varieties would be important. The expression of economically important traits (e.g., yield and quality) is governed by genes which can be identified by modern biotechnology. One such technology is marking with specialized tools. When a "genetic marker" is close to a gene of economic interest, the genetic marker can be used to identify plants which carry the economically important trait. This is important since selection using genetic markers can be done in the laboratory and thus genetic markers have the potential of increasing selection efficiency. The potential value of such technology is not known and requires much experimentation to describe. Genetic information can be used by computers to simulate expected outcomes during reproduction. We used computer simulations to characterize the potential utility of genetic markers to increase the efficiency of selection. Results suggest that genetic markers can increase selection efficiency and thus decrease the time for varietal development. This information helps clarify the potential benefits and risks involved in the implementation of this expensive technology. Public institutions and private companies can use the computer simulated theoretical expectations for selection in their investment decision-making.

Technical Abstract: From theoretical estimates of gamete frequencies, equations were constructed and used to calculate relative expected efficiency using codominant and dominant markers in marker-assisted selection (MAS). The frequency distributions of populations were affected by selection pressure intensity (i.e., number and time of selection). These frequencies were dramatically affected by linkage phase and distance, and thus a knowledge of linkage characteristics in populations is critical to the potential success of MAS. The efficacy of random amplified polymorphic DNA (RAPD) was evaluated through simulation. The most effective RAPD markers to use in MAS are flanking markers linked in repulsion phase to a target trait. Two repulsion phase RAPD markers that flank downy mildew resistance (dm) at a distance of 9.9 and 16.5 cM were used for evaluation. Theoretical estimates indicate that these markers would be expected to have a selection efficiency of 96 per cent when applied strategically in a MAS breeding program.