Molecular Approaches Speed Up Plant Breeding of Medical and Developing Country Crops

Molecular markers are identifiable DNA sequences, such as single nucleotide polymorphisms, that follow Mendelian laws of inheritance. Marker Assisted Selection (MAS) for improved crop traits offers a number of advantages over conventional phenotypic selection based breeding approaches, including the ability to stack multiple beneficial traits in fewer generations. However, MAS can only be applied if molecular marker maps for the crop of interest are available and statistical associations have been established between marker variants and traits of interest. Until recently, the identification of sufficient numbers of molecular markers and the development of marker maps that could be used for MAS had only been achieved for a relatively few commodity crops. With the advent of massively parallel DNA sequencing methods over the last few years the ability to rapidly identify sufficient numbers of molecular markers at relatively low cost has become possible. This coupled with high-throughput platforms that allow thousands of molecular markers to be assayed in parallel from thousands of individual DNA samples means that genetic maps can be rapidly constructed using computer algorithms. Consequently, the barrier to building genetic maps, linking markers to traits and performing MAS has been lowered allowing it to be applied to a range of marginal crops. Mutation breeding, whereby the variation available for selection is increased by mutagenesis, can also be made more effective if candidate genes can be identified and populations screened for variants in these. The step-change in DNA sequencing volume and cost-effectiveness has also greatly facilitated the identification of candidate genes, allowing so called ‘reverse genetic’ based mutation breeding to be applied to various marginal crops. This presentation will demonstrate the impact of these new technologies on the improvement of three such crops: Artemisia annua that produces artemisinin – the main drug that is used to kill the malaria parasite; hemp, which we are developing as a biorefinery crop because it produces a range of natural products including oil, fibre and pharmaceuticals and Jatropha curcas, a tree that is being developed for biodiesel production primarily in developing world countries.