Progress and prospects of marker assisted backcrossing as a tool in crop breeding programs

Abstract

Marker assisted backcrossing (MAB) is one of the most anticipated and frequently cited benefits of molecular markers as indirect selection tools in breeding programs. However, routine implementations of MAB in ongoing plant breeding programs are still scarce. Currently MAB of single gene is perhaps the most powerful approach that uses DNA markers effectively. Improvement of quantitative traits loci (QTLs) through MAB resulted to variable results ranging from limited success and/or even a failure to a few highly successful stories. A major constraint to the implementation of MAB in pragmatic breeding programs has been the high relative cost compared to conventional phenotypic selection. It is a popular misconception that a ‘DNA fingerprint’ is always to be preferred. To be useful to plant breeders, gains made from MAB must be more cost-effective than gains through traditional breeding or MAB must generate significant time savings, which justifies the additional cost involved. Currently, most national agricultural research systems (NARS) in Africa have either no or very limited facilities, skilled manpower, and financing for integrating molecular markers as part of their breeding programs. Therefore, conventional breeding methods remain the main option for NARS for many years to come, but targeted use of MAB may become a supplement if well-validated markers are developed or available through collaboration with the international agricultural research centers. This paper provides detail review of the current literature on MAB, including requirements and selected experimental results.