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Addis Ababa University (2016)

Genetic Diversity Analysis and QTL Mapping of Selected Traits in Sorghum (Sorghum Bicolor (L.) Moench

Disasa, Tesfaye

Titre : Genetic Diversity Analysis and QTL Mapping of Selected Traits in Sorghum (Sorghum Bicolor (L.) Moench

Auteur : Disasa, Tesfaye

Université de soutenance : Addis Ababa University

Grade : Doctor of Philosophy in Biology (Applied Genetics) 2016

Résumé partiel
Sorghum (Sorghum bicolor (L.) Moench) is one of the most important multipurpose crops grown globally. It can be used as food, feed, fiber and biofuel feedstock. In Ethiopia, sorghum is among the most important cereal crops accounting for 18 % of annual production and 16 % of land cover allocated to the entire grain crops including cereals, pulses and oilseeds. Despite this importance and huge potential as bioenergy feedstock, detailed study on characterization, identification and mapping of novel genes that code for sugar content related and drought tolerance traits using Ethiopian sorghum was lacking. Therefore, this study is aimed at germplasm collection, characterization, and identification and mapping of novel QTLs using both grain and sweet type of sorghum germplasm of Ethiopia. Both morphological and molecular evaluation of Ethiopian sweet sorghum germplasm was undertaken. Genotyping of 175 Ethiopian sweet sorghum genotypes alongside 27 improved accessions from eastern and southern Africa was undertaken. Two independent experiments were also carried out to identify and map QTLs associated to Brix and stay-green related traits using F2:3 segregating mapping populations derived from a cross between grain sorghum with stay-green feature (Sorcoll 163/07) and sweet sorghum (Gambella). A genetic map was constructed using 192 F2 populations genotyped with 76 SSR markers. Research was carried out to screen and compile the most informative SSR markers across some accessions. A total of 304 markers were used to identify the most polymorphic SSR markers across eleven farmers preferred sorghum genotypes. Combined analysis of variance for Brix and other morphological characters to evaluate 181 sweet sorghum accessions collected from the major producing regions of Ethiopia showed that there is a significant effect of the environment on all tested traits. Mean separation analysis revealed that collections from northern Ethiopia were found to be superior in terms of Brix degree. Collections from the rest of collection regions showed relatively low Brix mean value but characterized by higher biomass. Broad sense heritability estimate showed most characters are highly heritable except grain yield. Pearson correlation coefficients (r) of the seven traits presented Brix degree was negatively correlated to most of the traits. Cluster analysis based on the Brix and other morphological characters grouped the accessions into five clusters. The constructed dendrogram based on mean of collection zones for the tested traits also clearly put adjacent regions or zones together. All the tested markers detected 159 alleles and a high degree of polymorphism information content (PIC) averaging 0.69. A comparison between Ethiopian and improved accessions revealed higher allele numbers (124) in Ethiopian than improved accessions (92 alleles)

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