Assessment of genetic variations within and between populations of Marama Bean (Tylosema Esculentum (Burchell) Schreiber) based on Microsatellites (SSRS) and Intergenic spacer length variation markers in the Namibian germplasm
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Date
2010
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Abstract
Tylosema esculentum (Burchell) L. Schreiber is a herbaceous perennial drought tolerant legume that is endemic to the arid and semi-arid zones of southern Africa. Its agronomic potential is on the basis of its seed's nutritional composition that is comparable with soybean and peanut, the two mostly consumed legumes. In this study SSR markers were used to assess genetic diversity in natural populations of marama in the Namibian germplasm. Additionally, in the present study, the intergenic spacers (IGS) region of the large ribosomal DNA gene was amplified to assess length variation in marama bean. In the present study two to four alleles per primer pair were amplified from the 332 marama individuals among 11 populations. The study revealed that substantial genetic variation exists in marama populations and most of this variation (66.5) occurred within populations. The direct-count heterozygosities showed a substantial variation of 0.51 among populations. The mean Shannon diversity index for eleven marama populations assessed in this study estimated a higher genetic diversity in marama with a mean total diversity of (H' = 1.526). There were no significant differences (p 0.05) in the mean genetic diversity between populations. However, there were significant differences in the mean genetic diversity attained by different SSR primer pairs (p 0.05). Assessment of length variation in marama bean has disclosed a high intraspecific genetic variation (H'
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A thesis submitted in partial fulfilment of the requirements for the degree of Master of Science
Keywords
Beans Namibia, Plant genetics