Organisation du pool génique de Vigna unguiculata (L.) Walp. : croisements entre les formes sauvages et cultivées du niébé

Abstract

Organization of the genic pool of Vigna unguiculata (L.) Walp.: crosses between the wild and cultivated forms of cowpea. Cowpea (Vigna unguiculata (L.) Walp.) gene pool organization is studied on the basis of intra-specifi c crossing between cultivated (cv-gr. Unguiculata, cv-gr. Bifl ora) and wild forms of the species (var. spontanea, subsp. alba, subsp. stenophylla, subsp. pawekiae, subsp. baoulensis). The rate of crosses success, the rate of the obtained pods fruitfulness and the pollinic fertility of the hybrids F1 varied according to the wild taxa used. The highest rate of success was obtained for the crossings between cultivated and annual inbred form (40–79,3%). This result confi rms that var. spontanea is genetically closer to the cultivated forms than the other wild forms. Crosses between cultivated and wild allo-autogamous forms gave intermediate rates of success (17,8–57,9%) and a signifi cant reduction of the pollinic fertility of some hybrids F1. These observations suggest the existence of a genetic divergence between these two groups, however they share the same gene pool. The wild allogamous forms gave the weakest rates of success with the cultivated forms (3,1–40%) showing that they are genetically more distant of these last, compared to the other wild groups. The rates of crosses success are particularly weaker when the wild form subsp. baoulensis is crossed with the cultivated forms.