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This dissertation focuses on the molecular systematic analysis of the genus Corchorus (Malvaceae s.l.), investigated for the first time using nuclear rDNA ITS sequences, and addresses diversity of selected species, which were conducted using morphological, molecular, and flow cytometry methods. Prior to this study, little information was available regarding the biodiversity and potential use of jute (Corchorus species) in Ethiopian agriculture. The present study summarizes species'ecological distribution, use, and ethnobotany of Corchorus species in Ethiopia. About 13 species were recorded, ranking the country second in the total number of species in Africa. The study revealed low similarity in species composition between the regional states, indicating that each region has its own unique set of species. Farmers'perception, indigenous knowledge and folk taxonomy of jute species are more comprehensive in the southwest than other studied regions of the country. Although several jute species are found in Ethiopia, they are neither cultivated nor popularly used as leafy vegetables. This part of the dissertation emphasizes the need for creating of public awareness of jute in Ethiopian agriculture and recommends conservation measures for some threatened species. In addition to the species collected from Ethiopia, I included several other jute species in order to infer the phylogenetic relationships within the genus Corchorus. A molecular phylogenetic analysis was conducted using sequences of the nuclear ribosomal DNA internal transcribed spacer region (ITS) for 144 accessions representing about 48 species from entire pantropical distribution of the genus. In all phylogenetic analyses (maximum likelihood, Bayesian approaches, maximum parsimony), Corchorus is monophyletic when Pseudocorchorus is included. The majority of African Corchorus species formed a statistically highly supported and distinct clade separated from the rest of pantropically-distributed species. Species from Australia, New Caledonia and tropical America were nested within the African clade, indicating dispersals to the rest of pantropics out of Africa. Based on the taxa included in this study, the two cultivated species (C. olitorius and C. capsularis) shared a common ancestry with wild species of C. africanus, C. brevicornatus, C. pseudocapsularis, C. pseudo-olitorius, C. urticifolius, C. pilosus, C. orinocensis, and C. cunninghamii. The phylogenetic study indicated for the first time that Pseudocorchorus species were found to be members of Corchorus and shared a common ancestry especially with C. siliquosus, a species endemic to tropical America, and C. depressus, which is common to Africa and Asia. The monophyly of Corchorus/Pseudocorchorus seems, therefore, in accord with the overall very high morphological and anatomical similarities between both taxa. Thus, inclusion of the six Pseudocorchorus species into Corchorus might be appropriate. Nevertheless, I do not suggest a new formal classification of Corchorus/Pseudocorchorus, as additional molecular markers should be used to clarify the phylogenetic position of the taxa before taxonomic changes are made. Flow cytometric investigation of genome size variation in C. olitorius resulted in a 2C nuclear DNA content from 0.882 ± 0.004 pg to 0.942 ± 0.004 pg, with a mean of 0.918 ± 0.011 pg. The mean genome size variation in C. olitorius accessions from Africa was higher than in Asia. Genome size was positively correlated to seed surface area and growing elevation, and negatively to days to flowering. The estimated genome size of C. olitorius (449 Mbp) and C. capsularis (3 |
