Development of Microsatellite (SSR) and DNA Barcoding (MATK) primers for marama Bean (Tylosema Esculentum (Burchell) Schreiber) for Germplasm characterization of Namibian Genotypes
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Date
2010
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Abstract
Information on genetic variation of breeding materials helps maintain genetic diversity and sustains long term selection gain. Marama bean [Tylosema esculentum (Burchell) Schreiber] occurs naturally in arid, dry parts of Southern Africa and 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. Microsatellites are becoming the molecular marker system of choice because they are multiallelic and generally more informative. Recently, the development of SSR enrichment techniques has increased the efficiency of SSR characterization in new species. The overall aim of the project was to develop SSR's for detection of polymorphisms in marama bean. The microsatellite regions of the genome were the main focus and the matK gene was also explored for its potential to carry out a marama bean genetic diversity study. Microsatellite loci were isolated from the marama bean germplasm using a modified FIASCO enrichment technique. 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. Of the 80 primers designed, 76
were able to detect polymorphism. All polymorphic primers will be applied in the future to establish a trait linkage map for marama. Four of the SSR's were used for a genetic variation analysis and have proved to be useful and informative for genetic diversity studies. The matK gene product in marama bean was found to be half the expected size of the gene found in other legumes. The found homology with Tylosema fassoglensis (trnK gene) and Pisum sativum (matK gene) suggests that an identical region was amplified for Tylosema esculentum. A phylogenetic tree was constructed based on the matK sequences and the results suggest that the matK region can also be used in determining levels of genetic variation and for barcoding.
Description
A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Science
Keywords
Beans Namibia, Plant genetics