Screening Of Linkage Molecular Markers For Number Of Flue-Cured Tobacco Leaves

Flue-cured tobacco is an important economic crop mainly for harvesting leaves.The number of leaves per plant is one of the important quantitative traits that constitute the yield of tobacco leaves,and it is also closely related to the quality of tobacco leaves.To study the inheritance of the number of flue-cured tobacco leaves and the molecular markers closely linked with the number of leaves,it is of great significance to formulate the genetic improvement strategy of flue-cured tobacco leaves,improve the selection accuracy and selection efficiency,and implement the directional improvement of flue-cured tobacco leaves.In this study,the flue-cured tobacco variety NC82 and Bina No.1 were used as the parental material for hybridization,and the P₁,P₂,F₁,F₂ 4generation genetic research materials were constructed,and the plant quantitative traits were used.The genetic analysis of the number of flue-cured tobacco leaves was carried out by genetic hybrid genetic model.The Simple Sequence Repeats（SSR）markers were used to screen the SSR markers associated with the number of flue-cured tobacco leaves.The results are as follows:1.The average number of leaves in NC82 was 22.2,and the average number of leaves in Bina No.1 was 31.The difference in the average number of leaves between the two parents was extremely significant（P<0.01）,indicating that there were real and extremely significant genetic differences in the number of leaves between parents.The average number of leaves of NC82×Bina NO.1 positive and reverse F1 tobacco plants was 24.5 and 25.7,respectively.The difference of average leaf number between the two was not significant（P>0.05）,indicating that the number of flue-cured tobacco leaves was non-cytoplasmic.It is a nuclear inheritance.The number of leaves in the F₂ segregating population was tested by chi-square test.The number of flue-cured tobacco leaves was controlled by two pairs of major genes,and the quantitative traits affected by the micro-effects were inherited.2.The optimal genetic model for flue-cured tobacco leaves is MX2-EA-AD（2 equivalent additive main gene+additive-dominant polygene）,and its maximum likelihood value（Log_Max_likelihood_Value）is-207.7734,AIC value（Akaike’s information criterion）Value)is419.5469.Estimated by genetic effect parameters,the population average was 26.26117,the first pair of additive main gene and the second pair of additive main gene effects were-3.402,the multigene additive effect was 2.3707,and the multigene dominant effect was-2.145.The variance of leaf number phenotype was 12.5161,the main gene variance was 10.94404,the multivariate variance was 0.547,the environmental variance was 1.5757,the main gene heritability was87.4107%,the polygene heritability was 4.3701%,and the main gene+polygene heritability was91.7808%.It indicated that the heredity of leaf number was large,and the genetic effect of leaf number was mainly additive effect,additive effect>dominant effect.It is indicated that the selection of the number of leaves should be based on the selection of early hybrids,and the selection of backcross generations should be supplemented.3.From 1000 pairs of tobacco SSR markers,144 pairs of markers with different bands between the parental NC82 and Bina 1 leaf number genomic DNA amplification bands were screened,the ratio was 14.4%.The linkage marker screening and validation of the 6 equal-equivalent leaves near the isogenic pool showed that the PT50001,TM10588,TM20490 and TM10102 4 pairs were all linked to the leaf number traits.The PT50001 marker is distributed on chromosome 7,and the other three markers are distributed on chromosome 4,indicating that the number of leaves is controlled by two pairs of genes,and the number of leaves is controlled by two pairs of major genes,and the results of genetic analysis affected by micro-effects are simultaneously Match.A total of 507 F₂isolates were used as mapping populations.A linkage map containing TM10588,TM20490 and TM10102 was constructed by JoinMap@4.0 mapping and linkage disequilibrium test.The TM10588 was labeled as the relative start marker,TM20490 and TM10102.The genetic distances marked on chromosome 4 relative to the TM10588 marker were 4.2 cM and 5.3 cM,respectively,both less than 10 cM,indicating that the TM20490 and TM10102 markers are closely linked to leaf number traits.The above results showed that the number of leaves per plant of flue-cured tobacco was 2 pairs of additive main gene+additive-dominant multi-gene control quantitative traits,and the heritability was high.TM20490 and TM10102 markers were closely linked to the number of flue-cured tobacco leaves.The research results can provide theoretical basis and selection technique for the number of leaves of Bina No.1 as donor parent and oriented improvement of high quality variety NC82.