BETRAM KUOL, MARC J.J. JANSSENS, ABDALWAHAB ABDALLA
University of Bonn, Institute of Horticulture, Germany
University of Khartoum, Crop Science, Sudan
Drought is a major environmental abiotic stress that limits Sesame production in both marginal and adequate rainfall areas with long dry spell during the growing season. Improvement of cultivars for drought resistance is one of the major objectives of sesame breeding programs in the Sudan. Three phases of field investigations were carried out in collaboration with University of Khartoum to assess the extent of variability, study the inheritance and breed for drought tolerance in this crop.
Seventeen sesame genotypes of diverse origin were field tested under water stress and well-watered conditions across two locations in year 2000. A wide range of genetic variation was detected for the studied characters as well as among the genotypes. Genotypeenvironment interaction was significant for seed yield/plant and most of its components. Superior genotypes maintained highest yield/plant over two locations but in a different rank. Drought tolerance was assessed as the ratio of yield under water stress (Y) to the yield under normal irrigation (Y). (Y/Y) was moderately heritable, exhibited a weak correlation to seed yield and yield related traits, and indicated that seed yield and its attributes were sensitive to water shortage more than the morphological characters. (Y) was negatively correlated to drought tolerance (), it had heritability of (0.72) which suggests good prospective for improvement of this trait.
Based on crop performance in response to water treatments, four genotypes (three most drought tolerant and one most susceptible) were selected and used as parents in a crossing program. Mating designs of backcross, diallel, triallel (3-way cross) and quadriallel (double-cross) were used.
Components of genetic variation were investigated employing partial diallel fashion. Involvement of both additive and dominance gene actions was found to be important in inheritance of the studied characters. Variance components of epistatic nature and order of parents' involvement in crosses were estimated.
Keywords: Drought tolerance, mating design, sesame, Sesamum indicum, Sudan, water stress