Morphological and molecular characterization, yield determination and proteomic analysis of selected Bambara groundnut landraces in Lake Victoria basin, Kenya

Abstract

Bambara groundnut (BGN) (Vigna subterranea (L.) Verdc.) is a drought-resilient, nutrient-rich legume indigenous to Africa. Despite its nutritional and agronomic potential, BGN remains underutilized in Kenya’s Lake Victoria Basin (LVB), where diverse landraces are grown but lack comprehensive characterization. Knowledge gaps in morphological traits, yield potential, and protein diversity hinder effective classification, breeding, and utilization, especially due to overlapping physical characteristics and varying farmer preferences. Moreover, low yields across zones, largely due to recycling of non-adapted germplasm, highlight the need for zone-specific yield assessments and genetic diversity studies. This study aimed to evaluate the genetic diversity of BGN in the LVB using morphological traits, yield performance, and protein profiling. Specifically, it focused on identifying morphological characteristics of selected landraces across different agro-ecological zones and greenhouse conditions, determining yield variation, and assessing protein composition in high-yielding accessions. Six landraces (K1, K2, B1, B4, M2 and M4) were cultivated at three KALRO research sites (Alupe, Kibos, Oyani) and under controlled greenhouse conditions at Maseno University. A randomized complete block design with three replications was used. Morphological characterization followed the Vigna subterranea descriptor list, yield was assessed using standard agronomic metrics, and protein profiling was conducted via Bradford assay and SDS-PAGE. The study revealed high phenotypic diversity, especially in pod color, leaflet shape, and seed testa patterns. Shannon-Weiner indices indicated significant morphological diversity (H' > 1.6), with terminal leaflet shape and seed eye pattern showing the highest diversity (H' = 2.071). Quantitative traits such as plant height, pod number, and seed weight exhibited significant variation within and between zones (P ≤ 0.05), largely influenced by soil moisture availability. Accessions B1, M4, and M2 showed consistently high pod numbers. Cluster and principal component analyses differentiated landraces based on terminal leaflet area, seed weight, and pod number. Biplot analysis further identified B1 as a likely progenitor. Yield analysis revealed B4 (2.7 t/ha), M2 (3.3 t/ha), and M4 (1.6 t/ha) as the highest yielders at Alupe, Kibos, and Oyani, respectively. In greenhouse trials, B1 recorded the highest yield under irrigation (3.8 t/ha), while K1 excelled under drought (1.2 t/ha). Traits like flower number, pod number, and leaflet area correlated positively with yield (r ≥ 0.50). Among the top performers, M2 had the highest total protein content (0.123 mg/mL), with albumins being the most abundant protein fraction. SDS-PAGE revealed seven shared protein bands across landraces, with M2 uniquely expressing a 180 kDa band, suggesting potential as a molecular marker. In conclusion, the study demonstrated significant morphological and molecular diversity among BGN landraces in the LVB, identified high-yielding accessions, and discovered a unique protein marker in M2. These findings support the targeted selection and breeding of adaptable, high-yielding BGN varieties. The study recommends focusing on M2 and B1 in future breeding efforts and integrating protein markers into classification and improvement programs for underutilized BGN in Kenya.