Construction of Genetic Linkage Map of Burley Tobacco(Nicotiana tabacum L.) and Genetic Dissection of Partial Traits

The agronomic traits and chemical components are very important factors affecting yield and tobacco leaf quality.Dissecting genetic control of these traits can facilitate the breeding of new tobacco cultivars by marker-assisted selection(MAS).The objective of this study was to identify QTLs controlling partial agronomic traits and chemical components in burley tobacco.A double haploid(DH) population of burley tobacco was used to construct a molecular marker genetic linkage map.The DH population was derived from a cross between high quality cultivar Burley 37 with high nicotine content and Burley 21 with low nicotine content.The mapping population was planted in main production region of burley tobacco in Hubei province for two years to obtain repetitive phenotype data.On the basis of this map,QTLs for four chemical components including nicotine(NIC),total nitrogen(TN),total sugar(TS),total potassium(TK) of air-cured central tobacco leaf and six agronomic traits including plant height(PH),stalk circumference(LS),distance between nodes(PT),number of total leaf(LN),length of central leaf(L) and width of central leaf(W) were analyzed by using software Windows QTL Cartographer Ver.2.5.The results showed that a total of 112 AFLP loci and six SRAP loci assembled into 22 linkage groups(A1-A22) composed the whole linkage map spanning 1 953.6 cM with an average distance of 20.5 cM between adjacent loci.There were 25 distortion-segregation loci(17.0%) mainly clustering in linkage groups A1,A11,and A14.A total of eleven main QTLs including seven QTLs influencing chemical components and the other remaining four QTLs conferring agronomic traits were detected.Out of them,two(btnic1 and btnic2) QTLs were detected for NIC,two(bttn1 and bttn2) for TN,three(btts1,btts2,and btts3) for TS,one(btph) for PH,one(btls) for LS,one(btpt) for PT and one(btl) for L.However,no QTLs were detected for TK,LN,and W.The 11 main QTLs explained 12.3% to 26.4% of phenotypic variation of traits detected.Additionally,btnic1 and bttn1 respectively controlling NIC and TN showed a good co-segregation,indicating that there could be a certain unknown biological relationship between nicotine biosynthesis and nitrogen metabolism in tobacco leaf.The present study would provide a better understanding for the genetic control and further fine mapping of chemical components and agronomic traits in burley tobacco.