Multi-Location Field Evaluation of Bambara Groundnut (Vigna Subterranean (L) Verdc) for Agronomic Performance and Seed Protein.

Abstract

Bambara groundnut (Vigna subterranea) is one of the most important legumes cultivated primarily for food by smallholder farmers in Africa. It is an affordable source of protein and contributes to income generation as well as soil fertility. Despite its importance, it is cultivated largely for subsistence purposes in South Africa. Growers use landraces. The agronomic performance of the traditional varieties depends on environmental factors prevailing in a particular area. In Limpopo and Mpumalanga Provinces, there is no adequate information regarding the performance of bambara groundnut germplasm. The objectives of the study were to (i) determine the agronomic performance of Bambara groundnut across three contrasting locations in Limpopo and Mpumalanga provinces over two cropping seasons (ii) determine the genotypic variation in the seed protein level among 42 bambara groundnut genotypes. Forty-two bambara groundnut genotypes were evaluated under three different environmental conditions (Syferkuil, Thohoyandou and Nelspruit) over two (2013/2014, 2014/2015) seasons in a 7 × 6 rectangular lattice design replicated three times. Eight agronomic traits including dry shoot weight (DSW), number of pods per plant (NPP), pod length (PL), number of seed per pod (NSP), pod weight per plant (PWT), seed weight per plant (SWT), 100 seed weight (100-SWT) and seed yield (SYLD) were measured. The results showed that there were significant genotype x location interactions which demonstrated that the prevailing agro-ecological conditions at the test locations were distinct from each other. Five genotypes (‘BGN-19‘, ‘BGN-11‘, ‘BGN-12‘, ‘BGN-4‘and ‘BGN-34‘) attained >25.0% seed yield advantage over the local check ‘BGN-39‘. The results also showed that light brown coloured genotypes attained relatively higher seed yield compared to the other seed colours types. The cultivar superiority index (CSI) showed that three genotypes (‘BGN-12‘, ‘BGN-19’ and ‘BGN-34’) were the most stable across the test locations and attained >900.0 kg/ha on average. There were significantly high positive correlations between PWT and each of the three other attributes (SWT, 100 SWT and SYLD). In terms of seed protein, the results showed a poor relationship between seed yield and protein levels. ‘BGN-12’ which produced the highest seed yield, attained the lowest percent seed protein while genotype. On average, the genotypes contained 21.72% protein. The highest and lowest seed protein quantities were attained by the genotypes ‘BGN-42’ (25.17%) and ‘BGN-12’ (19.89%) respectively.