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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/3232

Authors: Dagimawi, Teshome
Advisors: Kassahun Tesfaye(Dr.)
Keywords: Ethiopia
Genetic diversity
Sesame (Sesamum indicum L.)
Copyright: Jul-2011
Date Added: 30-Jun-2012
Publisher: Addis Ababa University
Abstract: Genetic diversity assessment of genetic resources maintained at Gene-Banks has important implication for future improvement, conservation and collection activities. However, such information is not available for sesame collected by IBC, Ethiopia. Intersimple sequence repeat (ISSR) marker was used to assess the level of geneticdiversity, genetic structure and genetic distance, and to indirectly estimate the level of gene flowamong populationsof sesame in Ethiopia.A total of 120 (82 Ethiopian and 38 exotic) sesame accessions and six ISSR primers, five of which were dinucleotides (810, 818, 834, 844, 860) and one pentanucleotides (880) primers were used. DNA was extracted using a triple CTAB extraction method from silica gel dried bulked sample of five randomly selected individual plants per accession at the stage of three to four weeks after planting. A total of 58 clear and reproducible bands were amplified, out of which 44(75.86%) were observed to be polymorphic. The number of polymorphic loci ranged from four for primer-834 to eight for the other primers.Comparative assessment of Ethiopian accessions (considering as a single large population) verses exotic accessions indicated the presence of higher polymorphism among accessions collected from Ethiopia (75.85)than the exotic accessions (65.52). Primers 810, 818 and 860 showed the highest percent polymorphism (88.89%) and the least polymorphic bandswere scored by primer 834 which is only 40.00 %. Grouping Ethiopian accessions into administrative region-based populations and the exotic accessions in to country based populations showed samples from Welega were the most diverse,with gene diversity value of (0.26) followed by samples from Tigray (0.20) and Shewa (0.20). Samples from Gojam (0.10) and Sudan (0.12) were the least diverse. The average gene diversity relative to the overall population was 0.24 considering accession from different administrative region of Ethiopia and exotic accessions as independent population. AMOVA without grouping revealed that higher percentage of variation (94.09%) is attributed to the within population variation while the remaining variation is due to the among population variation (5.90%). Inter-population genetic distance (D) ranged from 0.031 to 0.165 for the overall population. Among the pairwise population comparisons made within Ethiopian populations,accessions from Welega and Harerge showed the highest genetic distance (0.16) and accessions from Shewa and Harerge show the least genetic distance (0.041). From the exotic accession,samples of South East Asia are distantly related to most of the Ethiopian accessions. Genetic distance between the other pairwise combinations of populations was very low, with the least genetic distance being between samples of Mexico and Tanzania (0.031).UPGMA analysis of Ethiopian sesame populations revealed two major groups and three outliers (Cultivated, Welega and Illubabore). The first major cluster again forked into two sub groups the first containing Tigray, Harerge and Shewa populations, while the second contained Gamo Goffa, and Wello populations. The second major cluster comprise of accessions from north western part of Ethiopia mainly from Gojam, Benishangul Gumuz and Gonder.In the 3D plot, with the exception of few accessions that come from Welega, Wello and Ilubabore, most of the individual accessions that represent different populations spread all over the 3D space.
Description: A Thesis submitted to the School of Graduate Studies, Addis Ababa University, in partial fulfillment of the requirements for the Degree of Master of Science in Biology (Applied Genetics)
URI: http://hdl.handle.net/123456789/3232
Appears in:Thesis - Biology

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