Responses of Bambara groundnut (Vigna Subterannea L. Verdc) landraces to field and controlled environment conditions of water stress.
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Date
2012
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Abstract
Bambara groundnut (Vigna subterranea L. Verdc) is a drought tolerant African legume
capable of producing reasonable yields where other crops may fail. However, it remains an
underutilised crop, owing to limited research, cultivated using landraces, of which scant
information is available describing their agronomy and genetic diversity. The aim of this
study was to evaluate the response of bambara landraces from different geographical
locations to water stress under controlled and field conditions. Seeds were sourced from
subsistence farmers of Tugela Ferry and Deepdale in KwaZulu-Natal (South Africa) and
Zimbabwe, and characterised into three seed coat colours: light-brown, brown and red.
Seed quality was assessed using the standard germination test. Vigour indices of
germination velocity index and mean germination time were determined. Seedling
establishment was evaluated using seedling trays using a factorial experiment, with four
factors: 1. provenance – (Tugela Ferry and Deepdale), 2. seed colour – (red, light-brown
and brown), 3. water regimes – (30%, 60% and 100% field capacity), and 4. soil media –
(clay, sand and clay + sand). Seedling leaf samples were used to evaluate proline
accumulation as an indicator of stress tolerance. A field trial was used to evaluate
productivity of bambara landraces under rainfed and irrigated conditions. A pot trial was
conducted under controlled environment conditions with three factors: temperature
(33/27°C and 21/15°C), water regimes (30% and 100% of crop water requirement) and
bambara landrace selections. Results showed no significant differences in germination
capacity between bambara landrace selections. Germination time differed significantly
(P<0.001) between bambara landrace selections. The Jozini provenance was shown to
perform best, followed by Zimbabwe, Tugela Ferry and Deepdale. Brown landrace
selections had higher (P<0.001) germination compared with red and light-brown
selections, respectively. Seedling establishment showed that emergence was higher
(P<0.001) at 100% FC compared with 60% FC and 30% FC. Emergence was higher (P<0.001) in the Sand+Clay mixture compared with Clay and Sand media. Dark-coloured
selections had higher (P<0.001) emergence compared with light-coloured selections.
Results from the field trial showed that the red landrace selections emerged better
(P<0.001) than the light-brown and brown landrace selections, respectively. Plant growth
was lower under irrigated compared with rainfed conditions. Stomatal conductance was
higher (P<0.001) under irrigated compared with rainfed conditions, whereas chlorophyll
content index was higher (P<0.05) under rainfed compared with irrigated conditions.
Results of the pot trial showed that emergence was significantly (P<0.001) affected by
temperature. It was higher at 33/27°C compared with 21/15°C (P<0.001). Dark-coloured
landraces had higher emergence compared with the light-brown landraces. Stomatal
conductance was lower at 30% ET relative to 100% ETc. There were no significant
differences between water regimes with respect to biomass, pod number per plant, pod
mass per plant, seed number per pod, seed mass per plant and harvest index. It is
concluded that seed colour is an important variable in the identity of bambara landraces.
Provenance plays a significant role in seed performance and there is a significant
interaction between provenance and seed coat colour. This study could be expanded to
obtain more data for crop improvement through inclusion of many sites and seasons for
better agronomic advice to farmers.
Description
Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.
Keywords
Bambara groundnut--KwaZulu-Natal., Bambara groundnut--Effect of stress on--KwaZulu-Natal., Bambara groundnut--Effect of water levels on--KwaZulu-Natal., Bambara groundnut--Varieties--KwaZulu-Natal., Bambara groundnut--KwaZulu-Natal--Growth., Bambara groundnut--Seedlings--Evaluation., Bambara groundnut--Seeds--Quality., Germination., Bambara groundnut--Effect of temperature on--KwaZulu-Natal., Theses--Crop science.