Recents developments in cowpea germplasm collection, conservation, evaluation and research at the Genetic Resources Unit

The history of the Genetic Resources Unit at the International Institute of Tropical Agriculture (IITA) was highlighted. By 1980, the unit engaged in characterization and evaluation of germplasm information. In order to strengthen the units activity and provide a better knowledge of Vigna, the government of Italy funded a project from December 1984 to December 1989. Information on the geographical distribution of Vigna were also given. The unit now maintains 923 accessions of wild vigna species and about 15,200 accessions of cultivated cowpea

Preservation of genetic resources by seed storage

Several ways exist of maintaining the genetic resources of crops. The cheapest and most convenient way is by storing seeds. However, not all crops can be preserved by storing their seeds, because they are either vegetatively propagated and/or do not produce seeds, or the period of their seed viability is short. Maximizing the longevity of seeds requires a good seed store and knowledge of the principles of seed preservation. This document discusses types of seed, techniques for preparing seeds for storage, factors controlling longevity of seed, standards of seed stores for genetic resources conservation, and design of seed stores

Wide crosses of Vigna food legumes

Many successful wide crosses among Asiatic cultivated Vigna species and between them and a wild species, V. trilobata, have been reported However, despite many attempts to cross the African cultivated Vigna species with wild Vigna species and the Asiatic cultivated Vigna species, there has been no success as yet. Nevertheless, crosses between cultivated and wild subspecies of V. unguiculata were fairly easy and their hybrids are fertile. Studies conducted at the International Institute of Tropical Agriculture (IITA) have shown that crossing barriers between V. unguiculata and several African wild Vigna species were due to abortion ofyoung embryos and pollen-pistil incompatibility. With more basic research on reproductive biology and tissue culture, and a larger number of crosses among species and genotypes, there will be a greater chance of success for wide crosses between V. unguiculata and wild Vigna species which possess some very desirable traits for the improvement of this cultivated specie

Conservation des ressources genetiques par le stockage des graines

Il existe pi usieurs facons de conserver les ressources genetiques des cultures. La methode la moins chere et la plus simple consiste a stocker les graines. Toutefois, ce n'est pas toutes les cultures qui peuvent etre conservees sous forme de graines, car certaines se propagent vegetativement et produisent ou ne pro• duisent pas de graines; quand elles en,produisent, la viabilite de celles-ci est courte. Pour prolonger au maxi-mum la duree de vie des graines, il faut un bon entrepot et la maitrise des principes de la conservation des graines. Ce Guide traite des types de graines, des techniques de preparation des graines pour I'entreposage, des facteurs afferents a la duree de vie des graines, des normes des entrepots de graines pour la conservation des ressources genetiques et de la conception des entre pats de grains

Embryological study of crosses between Vigna unguiculata and V. vexillata

Early embryogenesis up to 8 days after pollination was characterized in V. unguiculata. When crosses were performed between V. unguiculata and wild V. vexillata, seeds were not obtained due to crossability barriers. In most cases pollen tube growth was arrested in the stigmatic tissue. In the 15-20% of ovules which were fertilized, embryo development was normal up to the globular stage, but then (5-8 days after pollination) the embryo began to collapse