Isolation and characterization of microsatellite repeats in Marama bean (Tylosema esculentum)

Marama bean [Tylosema esculentum (Burchell) Schreiber] occurs naturally in arid and dry parts of Southern Africa, including Botswana, Namibia and South Africa. Due to the high nutrient value of the seeds and tubers, rich in protein, oil and starch, it is a potential crop for arid areas where few conventional crops can survive. The objectives of this study were to design microsatellite primers based on microsatellite repeats identified in Marama bean and to determine their ability to detect polymorphisms for use in diversity characterization. DNA fragments of T. esculentum containing microsatellite loci were isolated by enrichment of genomic DNA by a modified FIASCO technique and sequenced. Nine Marama bean microsatellite libraries enriched for (AAG)7, (GTT)7, (AGG)7, (GAG)7, (CA)10, (CT)10, (TCC)7, (CA)15 and (CAC)7 were created and thirty microsatellite primers based on the microsatellite regions of marama bean were designed and screened for polymorphism. Polymorphic microsatellites that were identified can be used as markers in future breeding programs. The screening for the polymorphic SSRs is being carried out to reach a target of 50 or more polymorphic SSR markers. It appears that the marama bean germplasm has abundant polymorphic microsatellites as 77% of the 30 loci screened initially were polymorphic.