Molecular mapping of important agro-botanic traits in sesame
AbstractSesame (Sesamum indicum L.) ((2n=26) is one of the most ancient oilseed crop of the world. The present study was undertaken to develop a molecular map of the important agro-botanic traits in sesame. Two sesame genotypes Chandana and TAC-89-309 that differ in respect of the important agro-botanic traits were crossed to study the inheritance of these traits. The F2 population along with the F1 and parents was evaluated under field conditions and observations were made on nine agro-botanic traits using International Board for Plant Genetic Resources (IBPGR) descriptor grading. For mapping trait related QTL, a genetic framework linkage map was constructed employing a mapping population of 120 F2 individual plants and effective 60 RAPD polymorphic markers chosen based on the study of parental polymorphism (23.07 %). The linkage map places the 60 markers on nine linkage groups spanning a total length of 1547.16 cM at an average distance of 25.78 cM between markers. These nine linkage groups could be covering about 60% of the map length of the genome. Length of the linkage groups ranged between 58.8 (Linkage Group 8) to 423.8 cM (Linkage group 9). The segregation and normal distribution observed in respect of most of the traits in the F2 population have been indicative that the mapping population had sufficient amount of genetic variability for mapping trait specific QTL. Seventeen QTL have been identified for the nine agro-botanic traits by single marker analysis. In all, 19 QTL have been identified by using QTL cartographer v 2.5. Of which, 7 and 12 QTL have been identified by Simple interval mapping and Composite interval mapping respectively. Two genomic regions - one on LG 1 and the other on LG 6 had more than one QTL. The marker interval between OPAE 15350 and OPD 6480 on the linkage group 1 has three QTL viz., leaf angle, capsule hair length and stem hairiness, while on LG 6 between the markers OPP 8380 and OPR 8980, two QTL for basal leaf shape and capsule hair density are distributed. In all, nine tightly linked markers for nine different traits have been identified with marker-QTL distance of < 2.6 cM. Out of the 19 QTL detected, five explaining high phenotypic variation are promising. These include one QTL for corolla colour, two for capsule shape and one each for capsule hair density and number of nodes.
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