University of Khartoum

Genetical and Cytogenetical Investigations on Sesamum Spp in the Sudan

Genetical and Cytogenetical Investigations on Sesamum Spp in the Sudan

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Title: Genetical and Cytogenetical Investigations on Sesamum Spp in the Sudan
Author: Khidir, Mohamed Osman
Abstract: Sesame varieties in the Sudan are numerous and exhibit great variability especially in seed colour. This thesis surveys and identifies 26 cultivated varieties and two wild species, studies the inheritance of seed colour in crosses involving white, brown and black-seeded varieties and the effect on the growth and productivity of colchicine treatment to induce autotetraploidy. The two wild species, Sesamum alatum Thonn and S. radiatum Schumach were quite distinct from each other and from the cultivated species (S. orientale L.). their oil content was much less than the cultivated species, being 30% and 25.8% respectively, while the oil content of the cultivated species was on the average 49%.The inheritance studies of the seed colour revealed that the black colour was dominant to the brown and the white colours, and the brown was dominant to the white. The black and the white colours were controlled by two factor pairs difference and gave a 9:3:3:1 ratio in F2 . Likewise, the brown and the white colours were governed by two factor pairs giving an F2 ratio of 9:3:3:1. The crosses between brown and black seeded parents gave an F2 ratio of 3:1 indicating a single factor pair difference. A factorial constitution for each parent was postulated on the basis of the above mentioned results; black: AABB, brown: AAbRbR and white: aabb. The presence of the olive colour as a common segregating class in the F2 progeny of the crosses white X black and the crosses white X brown led to the assumption that there was a basic gene in the brown and the black-seeded parents and it was designated A. The black seed colour was due to the complementary action of the basic gene and second gene B, while the brown colour was due to the action of the basic gene and another gene bR. The white colour was controlled by the double recessive genes.Two methods of colchicine treatment, namely seed immersion and growing tip treatment were used for the induction of autotetraploidy in a local sesame variety. The growing tip application proved to be more efficient than the seed treatment for the induction of abundant autotetraploid plants. The colchicine treatment resulted in a general retardation of growth even when very low concentrations were used. The treated plants differed from the untreated plants in certain morphological characters, mostly showing increase in size. At the flowering stage it was possible to differentiate more accurately between the diploids and the autotetraploids. The size of the pollen grains was used for detecting the autotetraploid plants.The chromosome doubling resulted in certain changes in the productive characteristics of the plants. The pods of the autotetraploid plants were shorter and broader than those of the diploid plants and contained fewer number of seeds. However, there was about 60 per cent increase in seed size but the oil content was reduced by 4 per cent. The induced autotetraploid properties were transmitted consistently to the offspring. The relative yielding capacity of the plants was reduced by about 55 per cent as a result of chromosome doubling
URI: http://khartoumspace.uofk.edu/123456789/16923
Date: 2015-11-05


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