Investigation of the Breeding Mechanism of African Yam Bean [Fabaceae] (Sphenostylis stenocarpa Hochst. Ex. A. Rich) Harms

Abstract

The many reported inherent nutritional potential in African yam bean (Sphenostylis stenocarpa (Hochst. Ex. A. Rich.) Harms) seem to provide platform for the need of its genetic improvement. A good understanding of the breeding system of the crop species is a needed criterion in plant breeding program. Four accessions of African yam bean (AYB) collected from the Genetic Resources Centre of the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria were grown out in a fifteen plants/accession row on a field at IITA, Ibadan (7.5°N, 3.9°E), Nigeria. Five pollination mechanisms were investigated as treatments on the four accessions. The four accessions set fruits and seeds in four treatments: plants left to open-pollination (A), plants isolated with fine net mesh (B), artificially selfed flowers (C) and inter-varietal cross-pollination (D). Emasculated flowers which were not pollinated (treatment E) produced neither fruit nor seed. Treatment A differed significantly (P<0.05) from B, likewise C and D. Fruit set percentage was higher in A (19.7-21.2) than B (18.3–18.7). Higher pollination/fertilization success (46.5%) was obtained in C compared to 32.3% in D. More seeds (88.6%) were set by self-pollination. The four accessions had a mean selfing rate of 89.8% and an outcrossing rate of 10.17%. The observed 1:9 allogamy: autogamy in this study could form the basis for developing the breeding strategy for the genetic improvement of AYB via hybridization.