Genetic Analysis of Several Important Botanic Traits in Flue-cured Tobacco

The joint segregation analysis method of mixed major gene plus polygene genetic model was used to study the inheritance of important botanic traits in flue-cured tobacco. Six generations (P₁, P₂, F₁, B₁, B₂ and F₂) from the crosses (Wanye×Coker319) were investigated. It was found that plant height, leaf number, leaf area and fresh leaf weight in flue-cured tobacco appeared to be a quantitative trait and their inheritances fitted to a mixed genetic model of two major genes with additive-dominant-epistatic effects plus polygenes with additive-dominant-epistatic effects (E0 model). Plant height and leaf number was mainly controlled by the additive effect and the epistatic effect of dominance × dominance. The additive, dominant and epistatic effects which the epistatic effect > the additive effect > the dominance effect of leaf area and fresh leaf weight were all important. Heritabilities of the major genes were estimated to be 57.53%, 42.63%, 30.32% and 44.26% in F₂. The inheritance of days of transplanting to flowering fitted to a mixed genetic model of two major genes with additive-dominant-epistatic effects plus polygenes with additive-dominant effects (E1 model) and it was mainly dominated by the epistatic effect of additive × additive, the additive effect, and the epistatic effect of dominance × dominance, the heritability of the major gene was 64.79% in F₂. The inheritance of stem girth and leaf mass per area fitted to a mixed genetic model of one major gene with complete dominant effects plus polygenes with additive-dominant effects (D3 model), stem girth was principally controlled by polygenes which additive effect was equal to its dominance effect, the heritability of the major gene was 2.48% and 38.71% in F₂. The inheritance of leaf index fitted to a mixed genetic model of one major gene with additive- dominant effects plus polygenes with additive-dominant- epistatic effects (D0 model), the additive effect and the dominance effect of the major gene was almost equal, the heritability of the major gene was 49.64% in F₂. Leaf length, leaf width, internodal distance and capsule weight fitted to a mixed genetic model of polygenes with additive-dominant-epistatic effects (C0 model), the heritability of the polygenes were 60.75%, 62.14%, 75.08% and 82.34% in F₂.