Phytic Acid, Protein, and Oil Contents and Their Relationship With Seed Quality During Seed Maturation of Bambara Nut (Vigna subterranea (L.) Verdc.) Landraces

Phytic acid, proteins, and oils are seed storage compounds that play a role in germination and seedling growth and may determine seed quality. The pattern of accumulation of these compounds and the relationship of their contents with the seed quality of the Bambara nut (BN) are poorly understood. Seeds of three BN landraces, AbiBam001 (black/cream), LocalBam (brown speckled), and TVSU544 (cream), were harvested from two field experiments at different maturation stages and tested for final germination percentage (FGP), germination velocity index (GVI), and seedling dry weight (SDW). Seed samples from the same experiments were analyzed for phytic acid and proximate composition. Kendall's ranked correlation was used to describe relationships between phytic acid, protein, and oil contents and the seed quality of the landraces. Results showed no differences in the phytate, protein, and oil contents of landraces during seed maturation (p > 0.05), except for the phytate content of AbiBam001 (p < 0.05), which increased in the first experiment. At mass maturity, AbiBam001 and LocalBam had higher phytate and less protein and oil contents than TVSU544, implying that seed coat color may influence the phytate, protein, and oil contents of BN landraces. Higher phytate content in landraces appeared to relate positively with FGP, GVI, and SDW and vice versa. Phytic acid may positively affect seed germinability in BN landraces with high phytate content but may affect it negatively in low-phytate landraces. The oil content of all landraces had negative correlations with most seed quality characteristics, suggesting that BN oils either are not priority reserves or play a minimal role in germination and seedling growth.