Seed quality characteristics of a bambara groundnut (Vigna subterranea L.) landrace differing in seed coat colour

Abstract

Bambara groundnut (Vigna subterranea L.) is an underutilised African legume that fits the same ecological niche as Arachis hypogea. It is still cultivated using landraces and little is known about their seed quality. The current study evaluated seed quality characteristics (viability and vigour) of a local landrace on the basis of seed coat and speckling colour (plain red, plain cream, black speckles and brown speckles). Standard germination and electrolyte conductivity (EC) tests were used to evaluate viability and vigour. Seed imbibition rate was evaluated using two imbibition methods (seed-testing water bath and seed soaking). For each method, seeds were weighed at intervals and their water activity determined. Electron microscopy was used to determine seed coat thickness. There were highly significant differences (P < 0.001) among landrace selections with respect to germination, EC as well as imbibition and water activity. Black-speckled landraces had the highest germination (87%) and the plain cream landrace selections had the lowest final germination (67%). Brown-speckled and plain cream seeds had the highest (1 400 μs g⁻¹) and lowest EC (36 μs g⁻¹), respectively. Imbibition rate and water activity showed much fluctuation. Electron microscopy revealed that brown-speckled seeds had the thickest (116 μm) and plain cream seeds had the thinnest (107.9 μm) seed coats. The study concluded that seed quality in bambara groundnut was associated with seed coat and speckling colour.

Keywords: electrolyte conductivity, electron microscopy, germination, imbibition, viability, vigour

South African Journal of Plant and Soil 2014, 31(4): 219–226