Seed quality and water use characteristics of a bambara groundnut (Vigna subterranea L.) landrace differing in seed coat colour.
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Date
2014
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Abstract
Bambara groundnut (Vigna subterranea L.) is an underutilised African legume that fits the
same ecological niche as Arachis hypogea (groundnuts). Because of its reported drought
tolerance and high water use efficiency there are now renewed efforts to study bambara
groundnut with a view to promoting it as an alternative crop in marginal production areas. It
is still cultivated using unimproved landraces, and little is known about their seed quality.
There is need for information describing aspects of their seed quality in order for farmers to
successfully produce the crop. The study evaluated seed quality and seedling water use
characteristics of selected seed coat colours of bambara groundnut. Lastly, the study
investigated the effect of water stress imposed on maternal plants on subsequent yield and
seed quality of bambara groundnut. A single bambara groundnut landrace was characterised
into four distinct selections based on seed coat and speckling colour; plain red, plain cream,
cream with brown speckles (brown speckled) and cream with black speckles (black speckled).
Seed quality (viability and vigour) was evaluated using the standard germination, electrolyte
conductivity and imbibition tests as well as water activity, seed coat thickness and
mineralogy. Seedling water use characteristics were evaluated under varying water regimes
(25%, 50% and 75% field capacity). Measurements included plant growth and physiological
(chlorophyll content index and chlorophyll fluorescence) responses up to 21 days after
planting; thereafter seedling water use efficiency was determined. Irrigation was withdrawn
thereafter in all water treatments to determine physiological and metabolic responses (total
soluble sugars, antioxidants and phenols) to terminal stress. A field trial was grown in
2013/14 summer season under irrigated and rainfed conditions. Yield and yield components
as well as subsequent seed quality (viability and vigour) of progeny was determined from
harvested material. Darker coloured seeds and seeds with similarly coloured speckles showed
better viability while the plain cream landrace selection was more vigorous. Seedling water
use efficiency in bambara groundnut improved with decreasing water availability. Drought
avoidance strategies and acclimation to water stress were also found to be present at the
seedling establishment stage. Yield was negatively affected by water stress. Subsequent seed
viability and vigour were respectively higher in seeds produced under irrigated and rainfed
conditions. The study concluded that although bambara groundnut is a water use efficient
crop, water stress may affect yield and subsequent seed quality.
Description
M. Sc. Agric. University of KwaZulu-Natal, Pietermaritzburg 2014.
Keywords
Bambara groundnut--Seeds--Quality., Bambara groundnut--Seedlings--Evaluation., Bambara groundnut--Effect of water levels on., Bambara groundnut--Varieties., Bambara groundnut--Yields., Theses--Crop science.