Cai Changchun

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.

Genetic Analysis of Resistance of Burley Tobacco to Black Shank with DH Population

The inheritance of resistance to tobacco black shank was analyzed with an invitro anther cultured doubled haploid(DH) population derived from F1 plants of the cross between burley tobacco varieties Burley37(P1,resistant variety) and Burley67(P2,susceptible variety).Black shank incidences were investigated in the P1,P2 and DH population inoculated with race 0 Phytophthora parasitica var.nicotianae in 2 consecutive years,and disease indexes were calculated.The resistance to black shank was analyzed with the major gene and polygene mixing inheritance model on the basis of plants quantitative character,and other genetic parameters of the DH population were also estimated.The results showed that black shank incidence and disease index were controlled by 2 pairs of complementary major genes plus polygene(E-1-7) and 2 pairs of equally additive major genes plus polygene(E-1-3),respectively.Heritability values of major genes were 54.14% and 50.68%,and those of polygenes were 26.60% and 19.31%,the number of efficiency factor of polygenes was 0.61 and 1.31,respectively.Therefore,the resistance to black shank of burley tobacco was conditioned dominantly by 2 pairs of major genes and polygenes.The heritance of resistance to tobacco black shank in tobacco cultivars is relatively stable in breeding practice.However,environmental factors,including temperature and humidity,also have some influences on the occurrence and epidemic of tobacco black shank.