Study On The Correlation Between Parental Genetic Distance And Heterosis Of F1 Hybrids

In order to explore the relationship between genetic distance and heterosis of flue-cured tobacco and provide a theory evidence for the selection of superior combination and the prediction of the heterosis.In this experiment,11 flue-cured tobacco varieties(lines)with significant differences in agronomic traits were formulated into 30 F1 generation combinations according to incomplete diallel cross design.The genetic distance and cluster analysis of flue-cured tobacco parents were carried out by morphological markers and SSR molecular markers respectively.The heterosis of agronomic,physical and chemical character in flue-cured tobacco was analyzed based on phenotypic traits of parents and F1 generation.Correlation analysis was made between the parental genetic distance and the F1 generation heterosis,the relationship between parental genetic distance and F1 generation heterosis was studied.(1)The genetic distance of the phenotypic traits of 11 flue-cured tobacco parents ranged from 0.93 to 4.19,and the genetic distance between GK2 and jingyehuang was the farthest.The genetic distance between Gexin-3 and Taiyan-8 was the closest.They are divided into four groups based on the threshold of 2.48,and Group I has two subgroups,totally five parents: Subgroup I1(GK2,HKDN2,HKDN8)and Subgroup I2(GK8,HKDN5);Group II consisted of two subgroups,including three parents: Subgroup II1(Taiyan-8,Gexin-3)and Subgroup II2(Coker371);Group III has two parents: Yanyan-97 and Anyan-2;Group IV has only one parent: jingyehuang.(2)A total of 59 pairs SSR primers amplified 163 bands with a polymorphism ratio of 97.5%.Each pair of primers detected 1-5 alleles with an average of 2.8 alleles.The genetic distance of SSR molecular markers in 11 flue-cured tobacco parents was 0.1098-0.4269,the average genetic distance was 0.2774,the genetic distance between GK2 and jingyehuang was the farthest,and the genetic distance between HKDN5 and HKDN8 was the closest.With the genetic distance of 0.71 as the threshold,11 flue-cured tobacco parents were divided into four groups,Group I has two subgroups,a total of five parents: Subgroup II(GK2、GK8),Subgroup I2(HKDN2、HKDN5、HKDN8);Group II has two subgroups,a total of five parents: Group II1(Coker371、Gexin-3),Group II2(Taiyan-8);Group III has two parents: Anyan-2,Yanyan-97;Group IV has only one parent: jingyehuang.(3)The variation amplitude of phenotypic traits of F1 generation was relatively large,the agronomic and physical character expression were superior to parents.Among them,the expression of phenotypic traits of GK8×Gexin-3,GK2× jingyehuang,HKDN2×Gexin-3,GK8×Coker371,HKDN8×AnYan-2 were relatively prominent.The overall expression of the average heterosis and heterobeltiosis of F1 generation is that the positive heterosis combination is more than negative heterosis combination,the mean value is greater than zero.GK2×jingyehuang,HKDN2×jingyehuang,HKDN5×jingyehuang and GK8×Coker371 are highly heterotic combinations.(4)The genetic distance of phenotypic traits has a significant correlation with agronomic traits(the plant height,stem girth,maximum leaf length and maximum leaf width),physical traits(the leaf length and leaf width)and chemical components(total sugar,total nitrogen,starch and nicotine).The genetic distance of SSR molecular markers has a significant correlation with seven agronomic traits indicators,physical traits(leaf length,leaf width,single leaf weight,leaf thickness and stem ratio)and chemical components(total sugar,total nitrogen,starch,nicotine,potassium).