Production of intraspecific F1 hybrids between wild and cultivated accessions of cowpea (Vigna unguiculata (L.) walp.) using conventional methods.
Cowpea (Vigna unguiculata (L.) Walp.) is an important food legume in the tropics. It belongs to the Phaseoleae (L.) tribe (Fabaceae family), it is diploid and its chromosome number is 22. Its gene pool includes the cultivated cowpea and its wild relatives, which are connected with Vigna subgenus, Catiang section. Cowpea has a great potential in increasing food legume production. The cowpea varieties, however, are susceptible to a number of insect pests, especially the pod borer Maruca testulalis and a pod sucking-bug complex (e.g.: Clavigralla tomentosicollis, Anoplocnemis curvipes and Riptortus dentipes), which cause severe damage. The crossing programme presented here exploits the variability existing in the wild African germplasm of V. unguiculata and cultivated cowpea. To incorporate the insect pest resistance into the cultivated cowpea economically, reciprocal crosses between wild forms and cowpea varieties were performed, using the stigmatic pollination methods at anthesis. Some barriers were found in these intraspecific crosses. In the majority of reciprocal crosses, the growth of the pollen tubes was arrested in the stigmatic tissue. Only 16.01% of the ovules were fertilised. In these ovules, embryo development was normal at about 20-25 days after pollination. The failure of the intraspecific crosses in about 80.7% of the cases is thus the result of the lack of fertilisation and the unfertilised ovules. There seems to exist considerable incompatibility within the primary cowpea gene pool. The breeding programme carried out under controlled conditions has proved to be less successful in developed cowpea intraspecific F1 hybrids. Further studies should concentrate on germplasm from Africa with documented resistance to major insect pests. In addition, the application of techniques for bypassing barriers to hybridisation of parent genotypes should enable these embryos to grow to plants.
Lelou
B
B
Ghent University, Faculty of Bioscience and Engineering, Laboratory of Tropical and Subtropical Agronomy and Ethnobotany Coupure links 653, BE-9000 Gent, Belgium. blelou@hotmail.com
Van Damme
P
P
D000818:Animals; D003433:Crosses, Genetic; D007887:Fabaceae / Q000235:genetics* / Q000254:growth & development / Q000469:parasitology*; D006430:Hemiptera / Q000254:growth & development*; D006790:Host-Parasite Interactions; D010572:Pest Control, Biological / Q000379:methods*; D013045:Species Specificity