DEVELOPING GENETIC MAPPING AND MARKER-ASSISTED BREEDING TECHNIQUES IN BAMBARA GROUNDNUT (VIGNA SUBTERRANEAN L.)

Bambara groundnut (Vigna subterranean L. (Verdc.)) is an underutilised African legume crop which shows a high degree of drought tolerance. It continues to be an important leguminous crop in tropical Africa and is grown mainly by women who are small-scale farmers in Africa under traditional low input agricultural systems. It is grown mainly for its protein and carbohydrate, as a fixer of agricultural nitrogen and for its high levels of drought tolerance. Genetic studies into this species could provide important data for breeding programmes and to enhance food security in sub-Saharan Africa. The main project work was to construct two initial genetic linkage maps for Bambara groundnut and to carry out a trait QTL analysis. Genomic DNA was extracted from 73 bulked lines (effectively F3) derived from a cross between the DipC and Tiga necaru landraces. A set of 94 pre-tested SSR primers designed from a 454-sequenced microsatellite-enriched library were tested for segregation in this cross. Thirty primers were polymorphic and revealed that the residual heterozygosity in this population was around 25%, consistent with an F₃ population. DArT markers for Bambara groundnut were previously developed and 236 polymorphic markers have also been applied in this study. The genetic map consisted of 231 markers in 25 linkage groups of two or more linked markers, totalling 498cM and covering a predicted 44% of Bambara groundnut genome. The high marker-marker linkage (at 87%) suggests a more comprehensive coverage. Nine QTL loci were identified on 7 LGs. A major QTL was identified for internode length on LG3, explaining 41% of phenotypic variation. The ‘Narrow’ map, in contrast with wide cross population, was constructed from two domesticated landraces and would be expected to segregate for agronomically important traits, rather than domestication traits. The development of molecular tools for mapping and QTL analysis potentially allows more rapid breeding progress to be achieved in this species.