Characterization of African Yam Bean (Sphenostylis stenocarpa) Mutant Lines using Phenotypic Markers

Abstract

Phenotypic characterization has been recognized as very important for the identification and selection of promising lines in improvement programs. This study aimed at characterizing and selecting early-maturing and high-yielding African yam bean (AYB) mutant lines at M2 generation. The experiment was carried out at the experimental field of the Institute of Agricultural Research and Training, Nigeria. The experimental design used was a randomized complete block design with three replications. Nineteen promising AYB M2 mutant lines were selected with their four parents (making 23 lines) and further evaluated for agronomic characters in the field. The results obtained revealed that coefficients of variation ranged from 3.23% (maturity) to 141.81% (seed yield/plant). The M2 mutant lines flowered and matured earlier than their parents and outyielded their parents by 62.64%. The principal component (PC) showed that the first four PCs accounted for 75.54% of the total variation. The first PC accounted for first flowering, 50% flowering, first podding, and 50% podding. The second PC was responsible for pod yield/plant and seed yield/plant, whereas peduncle length and pod length were associated with the third PC, while the fourth PC was responsible for maturity. The breeding lines were delineated into three heterotic groups with cluster I had three lines; members had the highest pod yield/plant (60.22 g), seed yield/plant (27.33 g), and early-maturing. Cluster II consisted of 17 lines with moderate pod yield/plant, seed yield/plant, and longest pod length. Cluster III contained three mutant lines; exhibited the lowest pod yield/plant, seed yield/plant, and longest peduncle. A highly significant association existed between seed yield/plant and pod yield/plant (r = 0.97**), but negatively correlated with first flowering (r=-0.23*) and 50% first flowering (r=-0.24*). Therefore, AYB lines identified could be utilized by plant breeders/geneticists to develop AYB varieties that are early-maturing and high-yielding in improvement programs.