A study of intraspecific hybrid lines derived from the reciprocal crosses between wild accessions and cultivated cowpeas (Vigna unguiculata (L.) Walp.)

Abstract

Cowpea (Vigna unguiculata (L.) Walp.) is an essential food legume in the (sub) tropical areas. Reciprocal crosses were performed using wild accessions for transferring genes of interest to cultivars (524-B/IT84S-2049). Of these, a low number of seeds were obtained because of crossing barriers. A seed sample of 17 F1 hybrids germinated after germination was 69.09%. A subdivision into seed sterility, partial seed fertility and seed fertility was observed. Seed sterility was possibly due to chromosomal disturbances that occur in endosperms and embryos during early seed development. In partial seed fertility, vigorous plants flowered about 128 DAE but no pods were formed because of floral abscission at anthesis. In plants of (524-B (♀) × tenuis (♀)) combination, partial sterility was caused by incomplete male sterility. In 13 F1 hybrids, viability among populations was reduced (67.25%). Eleven F1 hybrids were grown in the greenhouse to produce F2 seeds by natural self-pollination. Plants were characterised through using cowpea descriptors. Variability, in terms of morphological characters in adult F1 plants, was established. Differences in vegetative, inflorescence and fruit characters were described after full plant development. The results show that the adult F1 plants appear to be dominant for wild vegetative and inflorescence characters expressed by one or two of the parents in bi-parental and reciprocal crosses, for exception plants derived from crosses in which alba wild forms served as male parent showing the same morphological characteristics as the cultivated female parents, as evidenced by the traits inherited from cultivars. The heterotic status exhibited by emerged plants, supposes that the latter types inbred at the first generation confirm that the wild parents involved in these hybrids represent a wide diversity of germplasm. Seed characteristic studied in F2 has not shown segregation because of recessive type absence, suggesting that morphological traits should be monitored. Key words: Reproductive barriers, seed fertility, introgressive hybridisation, wild character inheritance.