Construction Of Linkage Genetic Map And QTL Mapping For Agronomic Characters And Chemical Quality Traits In Tobacco

The agronomic characters and chemical quality traits of tobacco were quantitative characters with polygenic control. To identify quantitative trait loci (QTL) for important traits in tobacco, a F2 population derived from the cross between flue-cured tobacco cultivars Honghuadajinyuan and air-cured tobacco SWU109 was used in phenotypic survey and SSR and SRAP analysis. Seven agronomic characters, i.e. leaf number (LN), plant height (PH), internode length (IL), stem girth (SG), length of the largest waist leaf (LWL), width of the largest waist leaf (WWL), and foliar fold (LF), and five chemical quality traits i.e. reducing sugar content (Su), potassium content (K), total nitrogen content (N), chlorine content (Cl), and nicotine content (NIC) were tested, which showed large correlations between each other. The main results in this study were as follows:(1) The construction of genetic map of tobaccoThe tobacco genetic map covered 1918.1cM of tobacco genome with 204 SSR markers and SRAP markers in 24 linkage groups. The linkage groups included 5 to 16 SSR and SRAP markers, with a length of 30.1cM to 132.9cM, and the average distance about 8.40 cM between two markers.(2) QTL mapping of agronomic characters of tobaccoQTL mapping was carried out using the composite interval mapping method. A total of 19 QTLs were detected from seven different agronomic characters, on the linkage of No.16,17,19, and 20, and a single locus explainable 3.56%-23.90% of the phenotypic variation. We detected two leaf number related QTLs, on the linkage of No. 16 and 17, and single QTL explainable phenotypic variation were 9.45% and 11.28%, of which qLN-17-2 was the main effect QTL to explain the largest variation. We detected three plant height related QTLs, on the linkage of No.2,17 and 19, and single QTL explainable phenotypic variation were 17.04%,7.60% and 7.91%, of which qPH-2-1 was the main effect QTL to explain the largest variation. We detected two stem girth related QTLs, both on the linkage of No.19, and single QTL explainable phenotypic variation were 12.52% and 23.02%, of which qSG-19-2 was the main effect QTL to explain the larger variation. We detected five internode length related QTLs, on the linkage of No.17 and 20, and a single locus explainable 3.56%-23.90% of the phenotypic variation, of which qIL-17-3 was the main effect QTL to explain the largest variation. We detected two length of the largest waist leaf related QTLs, both on the linkage of No.19, and single QTL explainable phenotypic variation were 16.27%and 21.36%, of which qLWL-19-2 was the main effect QTL to explain the larger variation. We detected four width of the largest waist leaf related QTLs, on the linkage of No.1,17 and 23, and a single locus explainable 9.13%-15.43%of the phenotypic variation, of which qWWL-17-2 was the main effect QTL to explain the largest variation. We detected one leaf fold related QTL, on the linkage of No.1, and explainable 11.44% of the phenotypic variation.(3) QTL mapping of chemical quality traits of tobaccoA total of 12 QTLs were detected from five different chemical quality traits, on the linkage of No.1,17,21 and 22, and a single locus explainable 4.01%-19.53% of the phenotypic variation. We detected three potassium content related QTLs, on the linkage of No.1 and 5, and single QTL explainable phenotypic variation were 4.01%, 10.89% and 18.07%, of which qKk-1-2 was the main effect QTL to explain the 18.07% variation. We detected one chlorine content related QTL, on the linkage of No.3, explainable 10.96% of the phenotypic variation. We detected four nitrogen content related QTLs, on the linkage of No.17 and 21, and a single QTL explained 7.94%-19.53% of the phenotypic variation, of which qNn-17-1 was the main effect QTL to explain the 19.53% variation. We detected three nicotine content related QTLs, on the linkage of No.21 and 22, and a single QTL explainable 10.63%,11.94% and 19.42% of the phenotypic variation, of which qNIC-21-1 was the main effect QTL to explain the larger variation. We detected one reducing sugar related QTL, on the linkage of No.8, and explainable 15.06% of the phenotypic variation.