Agro-morphological, nutritional and genetic diversity analyses of Bambara groundnut (vigna subterranea (L.) Verdc)
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Abstract
Bambara groundnut (Vigna subterranea (L.) Verdc) is a legume crop with potential to
address food insecurity in sub-Sahara Africa. However, a lack of agronomic, genetic and
nutritional information on the crop hinders its full potential utilization.
Nineteen Bambara groundnut lines were evaluated in the field in 2017 and 2018 at two
sites. The lines showed significant differences (P<0.05) for all the measured traits. Lines
such as IITA686, Cream and Uniswa Red-R were found to have superior performance
for multiple traits such as number of seeds per plant, seed mass per plant, plant height
and mid-leaf width.
The genetic variation among the Bambara groundnut lines was assessed using 20
polymorphic SSR markers The markers exhibited an average polymorphic information
content (PIC) of 0.57 and the observed heterozygosity was 0.58, showing that the lines
exhibited a considerable level of outcrossing. The lines were clustered into three groups
based on the principal coordinate analysis. The highest genetic distance was 0.60 between
Tiganecuru and S19. Lines such as IITA686, Cream and Uniswa Red-R that had good
performance for multiple agronomic traits occurred within a genetic distance of 0.40
making them genetically divergent enough for generating crosses for Bambara groundnut
improvement. The ash, fat, proteins, starch, calcium (Ca), iron (Fe), potassium (K),
magnesium (Mg), manganese (Mn), phosphorous (P), sodium (Na), copper (Cu), and
zinc (Zn), acid detergent fiber (ADF) and neutral detergent fiber (NDF) contents were
determined in the Bambara groundnut lines using combustion and chemical digestion
procedures. The nutritional content varied significantly (p<0.05) among the lines with
lines S19, Gresik, Pong-Br-UNK, Pong-Cr exhibiting high means for starch and protein
content ranging from 11.05 to 11.94%. Genotypes Mix, Pong-Br-UNK, 42-1, Gresik,
Uniswa Red-R, and Brown were clustered together based on their high starch, Na, Ca,
fat, and Mn contents. The negative correlations among some of the nutritional content
would be a challenge for simultaneous selection to breed nutritious Bambara groundnut
lines. The lines with high content for multiple nutritional elements such as 211-57, Pong-
Br-EN and Uniswa Red-G were recommended for production.
It was imperative to determine interrelations among agronomic traits and nutritional
content with seed mass for indirect selection. Among the agronomic traits, number of
seeds (NS r=0.58, p<0.01), number of healthy seeds (NHS, r=0.51, p<0.05) and plant
height (PH, r=0.45, p<0.05) exhibited the strongest associations with seed mass. These
traits had NS, NHS and PH high direct effects on seed mass of 2.04, 1.72 and 0.60,
respectively. These findings provide a means to facilitate indirect selection of genotypes
with high seed mass productivity via proxy.
Overall, the study found significant agro-morphological and genetic variation among the
Bambara groundnut lines, which would be a prerequisite for Bambara groundnut
improvement. The superior lines identified for multiple traits and genetic divergence were
IITA686, Cream and Uniswa Red-R.
Key words: Agro-morphology; Bambara groundnut; Genetic variation; Seed quality
Description
Doctoral Degree. University of KwaZulu-Natal, Pietermaritzburg.