Cowpea Genomics
Cowpea (Vigna unguiculata L. Walp.) is both one of the most important food and forage legumes in the semi-arid tropics and a valuable and dependable commodity for farmers and grain traders alike. Of the ~21 million acres grown worldwide, 80% of cowpea production takes place in the dry savannah of tropical West and Central Africa, mostly by poor subsistence farmers. Despite its economic and social importance in the developing world, cowpea has received relatively little attention from a research standpoint and remains to a large extent an underexploited crop.
Among the major goals of cowpea breeding and improvement programs is the stacking of desirable agronomic traits, such as those governing abiotic stress (drought, salinity, and heat) tolerance, photoperiod sensitivity, plant growth type, and seed quality with resistances to the numerous bacterial, fungal, and viral diseases and insect, invertebrate (nematode), and herbivorous pests. The use of marker-assisted selection and other molecular breeding venues for tracking single gene traits and quantitatively inherited characteristics will likely increase the overall efficiency and effectiveness of cowpea improvement programs in the foreseeable future and provide new opportunities for development of cowpea as a food staple and economic resource.
Cowpea, with a genome size estimated at 620 Mbp, has one of the smaller genomes present in leguminous plants. Supported by the Kirkhouse Charitable Trust, a philanthropic organization based in the UK, the Cowpea Genomics Initiative (CGI) was undertaken with the aim of using reduced representation sequencing (methylation filtering) to capture the gene complexity of cowpea without the laborious task of complete genome sequencing. The project is now complete and yielded just slightly greater than 250,000 genespace sequence (GSS) reads and approximately 160 Mb of total sequence. (The results of the analysis can be viewed at http://cowpeagenomics.med.virginia.edu/ ).
Our current work seeks to leverage the cowpea genespace sequence data and modern molecular-based technologies, in combination with conventional breeding strategies, to increase the speed at which a greater number of superior-performing, well-adapted cowpea varieties containing pyramided agronomic productivity, disease and pest resistance traits can be delivered to local farmers. A longer-term goal of our work is to conduct transcriptomic, proteomic, and metabolomic analyses to understand the basic biology of host and non-host resistance to Striga and Alectra parasitism, and the control of key agronomic characteristics such as drought tolerance, photoperiodic control of flowering, and seed nutritional quality.
