关键词: 番茄, 果脐大小, 数量性状, 主基因+多基因模型, 遗传分析

Abstract:

【Objective】 This study was conducted to perform a genetic analysis of tomato blossom-end scar size, with the aim of enhancing selection efficiency for this trait, accelerating the breeding process for small scar tomatoes, and laying a foundation for discovering key genes controlling blossom-end scar size and the genetic improvement of tomato varieties.【Method】 A small blossom-end scar line (P₁) was crossed with a large blossom-end scar line (P₂) to obtain F₁. The F₁ was self-pollinated and backcrossed with both parents to generate F₂, BC₁P₁ and BC₁P₂ populations. Blossom-end scar size and blossom-end scar index were evaluated across the six generations during the red ripening period of fruits. Genetic analysis was performed using the major gene plus polygene mixed inheritance model. The SEA software was employed to fit 24 potential genetic models. Candidate models were selected based on the maximum likelihood value (MLV) and Akaike’s information criterion (AIC), and the optimal genetic model was determined by integrating the results of the Smirnov test, Kolmogorov test, and homogeneity test. Finally, based on the optimal model, the least squares method was used to estimate genetic parameters, including additive effects, dominance effects, epistatic effects, as well as major gene heritability and polygene heritability.【Result】 The differences in blossom-end scar size between the parental lines were extremely significant. At 55 days after the peak flowering period, the average blossom-end scar size and scar index of the large blossom-end scar parent (P₂) were 9.44 times and 8.29 times greater than those of the small blossom-end scar parent (P₁), respectively. The average blossom-end scar size and blossom-end scar index of the F₁ population were intermediate between the two parental lines. The BC₁P₁, BC₁P₂ and F₂ populations exhibited continuous variation in both blossom-end scar size and blossom-end scar index, with a wide range of variability and coefficients of variation ranging from 61.2% to 87.4%. The frequency distribution of the F₂ population showed a continuous skewed normal distribution. Genetic model analysis suggested that the optimal model for tomato fruit blossom-end scar size was a mixed two major gene plus polygene inheritance model with additive-dominance-epistatic effects (MX2-ADI-ADI). The heritability of major genes in the F₂ population was 93.05%, while the polygenic heritability was 4.68%. The two major genes mainly control this trait through negative additive effects. In terms of dominance, the first major gene tended to decrease the fruit blossom-end scar size, whereas the second major gene tended to increase it. These two genes showed partial dominance, with the second having a stronger dominant effect. Additive × additive and dominance × additive interactions increased blossom-end scar size, whereas dominance × dominance and additive × dominance interactions decreased it. 【Conclusion】 Tomato blossom-end scar size is a quantitative trait principally controlled by two major genes.

Key words: tomato, blossom-end scar size, quantitative trait, major gene plus polygene model, genetic analysis