Molecular, Environmental And Nutritional Evaluation Of Bambara Groundnut (Vigna Subterranea (L.) Verdc.) For Food Production In Namibia

ABSTRACT

Bambara groundnut (Vigna subterranea (L.) Verdc.), an indigenous African legume valued for its drought tolerance, is popular in most parts of Africa. The study aimed to study environment effects on six landraces of Bambara groundnut (Nam 1759/3, Uniswa Red, S19/3, KFBN 9709, KFBN0105 and KFBN 0116) and to evaluate their molecular and nutritional compositions. The effects of different sowing dates and watering regimes on the growth and development of the landraces were studied. There were two sowing dates; one in the hot season and dry one late in the season during winter season. There were also two watering regimes; one where watering was done twice a week until harvesting and a drought treatment with no irrigation until final harvest. Parameters recorded included germination percentage, water use efficiency and crop yield. Genetic diversity in the 6 landraces of Bambara groundnut was evaluated using Random Amplified Polymorphic DNA (RAPD) and microsatellite markers. Nutritional evaluation was done on the six landraces by doing proximate analysis using the association of official analytical chemists’ methods. The study on acceptability, processing and utilization of Bambara groundnut in Namibia was done through a survey using a questionnaire to collect data. The questionnaire was presented to farmers and consumers of Bambara groundnut in the northern part of Namibia, where the crop is mainly consumed. No significant difference was observed among the different landraces between the two watering regimes as far as growth and development analysis was concerned. Field sown earlier in the year gave a larger harvest (204.396 – 336.535kg/ha) and the field sowed during the winter season doing extremely poor (11.778 – 65.125kg/ha). All landraces showed significant difference among the different sowing dates (χ 2 = 9.269, χ 2 = 9.846, χ 2 = 8.000, χ 2 = 9.269, χ 2 = 9.269, χ 2 = 9.302). Looking at their yield at harvest, the landraces were classified based on BAMnut Model – Crop Biomass and Pods Model and they ranged from unsuitable (Uniswa Red) to moderately suitable (KBFN 0105). Calculated water use efficiency showed that in winter the plant produced more per kg water than the ones in hot seasons. Strangely enough, some landraces produced more yield per kg water in non-irrigated plots than irrigated. RAPDs revealed high levels of polymorphism among the landraces. Polymorphism ranged from 57% to 100% with an average of 85% for the 7 RAPD primers evaluated, while microsatellites gave low levels of polymorphism ranging from 0% to 100%, with average polymorphism of 29%. All landraces were shown to be closely similar with the lowest similarity at about 88% similarity, and highest similarity of 98% between Nam 1759/3 and KFBN 9709. The low Shannon indices (0.426 – RAPDs and 0.093 – microsatellites) indicated a low genetic diversity among the six landraces The results obtained for nutritional evaluation of the six landraces, were consistent with previous studies on Bambara groundnut seeds. Moisture content ranged between 7.3% and 7.8%, ash content from 3.4% and 4.1%, fat content 2.1% and 3.9%, protein content 18.2% and 22.2%, and carbohydrates between 63.0% and 66.6%. There was no significant difference for carbohydrates, fats and protein contents among the different landraces as far as nutrient content was concerned among the different landraces (χ 2 = 2.720, χ 2 = 8.440, χ 2 = 3.090, χ 2 = 8.520, χ 2 = 6.440, χ 2 = 6.293) and between the irrigated and non-irrigated plots (Z = -1.993, Z =-1964, Z =-1.964, Z =-1964, Z =-1.964, Z =-1.964).