Developing Genetic Mapping and Marker-Assisted Breeding Techniques in Bambara Groundnut (Vigna Subterranean L.)

Abstract

Bambara groundnut (Vigna subterranea 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 F 3) 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 F 3 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.

Exploration of Bambara Groundnut (Vigna subterranea (L.) Verdc.), an Underutilized Crop, to Aid Global Food Security: Varietal Improvement, Genetic Diversity and Processing

“…Over the past twenty years, various molecular markers for analyzing genetic diversity, specifically designed for Bambara groundnut, were documented to either oppose or validate the reports on phenotypic descriptors (Table 3; [93]. Numerous studies have discussed ways that molecular markers can: offer information and knowledge on genetic diversity in Bambara groundnut [93], determine heterozygosity for the purification of seed [94], link germplasm to specific features such as the geographic region [45], function in quality regulation and can be useful in realizing breeding objectives [77]. Similarly, various studies have been conducted to explore the genetic mechanism of significant traits, such as leaf appearance, stress tolerance [95,96] and can provide a basis for the comparison of crops, with and without complete genome sequences, to pave the way for the translation of positional data into underutilized crops [97].…”

“…On average, a yield of 0.85 t ha −1 is achievable in Bambara groundnut [50]; however, the crop has been reported to have a genetic potential to produce up to 4000 kg ha −1 [106]. Reports by Somta et al [94] and Molosiwa et al [76] advocated Bambara groundnut being individual plants that are extremely inbred. Nevertheless, farmer landraces are quite a mixture of (mostly related) inbred lines and molecular evaluation, and this has shown that this condition persists even amongst the released varieties [107].…”

“…Nevertheless, farmer landraces are quite a mixture of (mostly related) inbred lines and molecular evaluation, and this has shown that this condition persists even amongst the released varieties [107]. An average of 1.3% heterozygosity was reported by Somta et al [94], with the exception of ten accessions from Burkina Faso and three accessions from Guinea, which had higher heterozygosity (2.99% and 4.99%, respectively), signifying a greater chance of outcrossing in their history. Equally, Molosiwa [65] reported 12 SSR markers used on 123 accessions, which indicated that the inbreeding coefficient ranges between 0.9 and 1.00, with average heterozygosity observed at 0.01; therefore, single seed descent (SSD) line advancement can be the first step in the development of near homozygous pre-breeding Bambara groundnut materials.…”

“…Higher throughput genotyping was achieved by the development of dominant DArT, which enabled the hybridization system-based array-genotyping, comprising four key subpopulations identified out of 40 genotypes collected from nine countries, as indicated by 554 DArT markers [45,99]. However, despite the feasibility of transferring SSR markers to closely related species, only 20 amplifiable SSRs out of 178 from Vigna unguiculata, Vigna angularis and Vigna radiata were identified as informative among 240 accessions of Bambara groundnut [2,94]. The discovery of the next-generation sequencing aided the optimization of additional 74 SSR markers from a leaf transcriptome [61,77].…”

Identification of Gene Modules Associated with Low Temperatures Response in Bambara Groundnut by Network-Based Analysis

“…Verdc , 2 n = 2 x = 22) is a nutritionally rich, underutilised, indigenous African legume crop and mainly grown for its protein rich seed. This crop continues to be the third most important food legume crop after groundnut and cowpea in semi-arid Africa [ 1 , 2 ]. Due to its good seed nutritional values, particularly for the protein component in developing country diets, bambara groundnut has been receiving increased interest and could undergo a shift from subsistence crop to a cash crop i.e., bambara groundnut has been canned at a commercial level [ 3 ].…”