Cowpea seems to be an ideal candidate for proving the potential benefits of genetic transformation. As it is attacked by a wide array of insect pests, a genetically modified cowpea with highly effective insect-resistant genes would definitely have a great positive effect in Africa. However, the cowpea wild progenitor is encountered over most of Africa and it can hybridize freely with domesticated cowpea varieties. Therefore, the main concern with genetically modified cowpea would be that this efficient insect-resistant gene would move from domesticated to wild populations. Very likely, fitness of the wild plants would improve, and the worst scenario would be if the wild cowpea turned into an aggressive weed devoid of any predators. Considering that wild cowpea is already a weed with good colonizing potential, this worst scenario cannot be ruled out at this stage.

Results from the first phase of the project, ‘Assessing the risk of transgene dissemination associated with the introduction of genetically modified crops in Africa using cowpea as a model’, show that hybrids between wild and domesticated cowpea (as well as their progeny) are fit. Importantly, they can easily take advantage of their inherent protection against insects to boost their seed production.

Isozyme analysis of natural populations as well as source and sink trials show that outcrossing rates and levels of gene flow fluctuate considerably during the year. Since cowpea flowers are large, large insects are required, and pollinator species (mainly leaf-cutter bees, Megachile, and carpenter bees, Xylocopa, but not the common bee Apis mellifera) are not numerous. Therefore, fluctuation of the pollinating bee populations and competition between cowpea and other species for pollinator services can explain these variations in outcrossing rates and gene flows.

An amplified fragment length polymorphism study of introgressed wild plants did not show any segregation distortion in the heritability of domesticated genes, and pollen competition studies show that although eastern African wild cowpea pollen is faster, there are no speed differences between western African wild pollen and domesticated pollen.

However, floral biology study suggests a way of preventing gene flow. The peak of bee activity in the morning is related to sunrise time while time of the opening of the cowpea flower fluctuates little during the year. Therefore, if domesticated cowpea flowers open late, much later than the peak of bee activity, or do not open at all, gene flow can be greatly reduced. Bee activity suggests another way to prevent gene flow. Through nectar aroma, bees seem to detect the aroma level of the flowers and do not visit empty flowers. Changing flower aroma could be a second way to prevent gene flow.