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Knowledge of genetic diversity within crop species and the nature of their breeding systems are critical for crop improvement. These determine the appropriate species specific breeding methodologies to deploy. Genetic diversity analysis is an ongoing process in the breeding programmes of 'major crops', which is used to direct or re-direct breeding objectives (especially selection of parental lines). In this regard, the importance of such information in 'underutilised' or 'minor' crop species, which largely exist as landraces with little information about their genetic diversity and breeding systems, becomes very important. One such important underutilized crop species which could contribute positively to global food security is Bambara groundnut ( Vigna subterranea (L.) Verdc.). We present here an overview of the past two decades of genetic diversity analysis of Bambara groundnut landraces. Various genetic diversity analyses of the available germplasm for the crop using phenotypic descriptors and molecular marker technologies have been reported. Generally, most of these studies lack adequate representation of the available global germplasm. For those studies that involved relatively a large germplasm collections (above 100; sampled from different agro-ecologies) the marker density employed in these analyses has been so far relatively low. Specifically, for breeding systems, high genetic diversity and low heterozygosity have been reported across the germplasm analysed in this highly cleistogamous species. In terms of population structure, the West African and the Southern African accessions appear as distinct clusters. This raises the possibility of the southern African region a secondary centre of domestication or diversity for the crop. [ABSTRACT FROM AUTHOR]

We report here the development of 75 SSR markers for Bambara groundnut through various sequencing approaches and the subsequent utilization of these SSR markers and other marker types (DArT Arrays) for the analysis of genetic diversity, population structure and the selection of pure lines from landraces. To assess the level of genetic diversity in Bambara groundnut landrace collections, 68 and 201 polymorphic SSR and DArT markers, respectively, were assayed against 24 single individual seed from a core collection of landraces. Polymorphic information content (PIC) ranged from 0.08 to 0.89 with an average of 0.42 across all SSR polymorphic markers, with observed ( Ho) and expected ( He) heterozygosity of 0.01 and 0.5 respectively. For the population structure analysis, 12 SSR markers selected as highly polymorphic from the initial screen were assayed against 123 landrace accessions. The average PIC across the 12 SSR was 0.66 with an average Ho of 0.02 and an inbreeding coefficient ( f) of 0.98, suggesting that seed derived from a single plant essentially represents an unselected variety. Based on the low level of Ho and high f observed in the landrace samples, a subset of 35 genotypes derived from the landraces were advanced for field trials in Botswana and scored for 37 phenotypic traits. These 35 individual genotypes were ranked for agronomic performance based on yield component factors and other qualitative traits after field evaluation. Five genotypes with good yield potential and adaptability were recommended as potential varieties for Botswanan agro-ecology. [ABSTRACT FROM AUTHOR]

Bambara groundnut an indigenous crop of African origin is drought tolerant and the third most important leguminous crop in Ghana and Sub-Saharan Africa. In order to assess the level of genetic diversity within a small collection of Ghanaian landraces, molecular analysis was performed using microsatellite markers alongside characterization of morphological features. Genetic distance based on Jaccard's similarity coefficient from the SSR marker analysis ranged from 0.48 to 0.9 among the landraces. 80 individual genotypes were clustered into 17 units with substantial levels of inter- and intra-landrace polymorphism. The analyses of variance from the morphological characterization for all quantitative traits were statistically significant ( p < 0.05) except for terminal leaflet width. The first 4 principal components accounted for 41.97, 20.15, 13.39 and 9.81 % respectively of the morphological variations among the landraces. Qualitative traits however accounted for less of these variations. The results of the present study support the availability of high level of polymorphism within the collection of bambara groundnut analysed. This report is useful to crop improvement and germplasm conservation of bambara groundnut in Ghana. [ABSTRACT FROM AUTHOR]