Genetic analysis of floral traits in F1 hybrids of Hongxun No. 1×Double-flowering crabapple

【Objective】Ornamental crabapples (Malus spp.) are primarily distributed across the Eurasian continent and North America. Due to their vivid flower colors, concentrated blooming periods, and abundant flowering, ornamental crabapples have been widely applied in scenic areas, gardens, urban greening, and container gardening. Many ornamental crabapples in China were introduced from North America and Europe, and hybrid breeding was primarily focused on improving fruit traits of dessert apples. As a result, the breeding of crabapples started relatively late and mainly targeted descriptive traits such as flowering time, phenology, and flower color. Heridity of quantitative floral organ traits has been far from clear. A deeper analysis of the genetic variation and inheritance patterns of floral traits in the F1 progeny derived from the cross between Hongxun No. 1 and Double-flowering crabapple can provide a foundation for breeding ornamental apple cultivars.【Methods】A total of 204 F1 hybrid individu-als derived from the cross between Hongxun No. 1 (Malus spp.) and Double-flowering crabapple (Malus spp.) were investigated for five quantitative floral traits (flower diameter, petal count, stamen count, pistil count, and peduncle length) and two descriptive traits (flower color and petal type: single or double). We organized experimental data using IBM SPSS Statistics 27, and generated figures with Origin 2018. The parental values (P1 and P2), variances (Vp1 and Vp2), mid-parent value (MP), hybrid population mean (F), standard deviation (S), variance (VH), coefficient of variation (CV, %), transmissibility (Ta, %), broad-sense heritability (Hb 2 , %), heterosis rate (H, %), and high-parent rate (HH, %) were calculated to analyze the inheritance patterns. The mixed major gene plus polygene inheritance model was used to analyze the genetic models of the five quantitative traits in the F1 population using the SEA software package. The optimal genetic model was selected based on the minimum Akaike’s Information Criterion (AIC), and the corresponding major gene effects were estimated using the least squares method.【Results】Phenotypic identification of five quantitative and two descriptive traits in 204 F1 progeny revealed rich genetic diversity. The flower color in the F1 population showed clear segregation into four phenotypes: white (4.46% ), pink (50.50% ), red (33.66% ), and purplish- red (11.38% ). The petal type segregated into single- petaled (82.57% ) and double- petaled (17.43% ) individuals. Variants such as white single-petaled and red double-petaled were observed, demonstrating the high potential for selecting elite ornamental germplasm. All five quantitative traits showed varying degrees of phenotypic variation. The flower diameter had the lowest coefficient of variation (14.13% ) and exhibited high genetic transmissibility and broad-sense heritability. Its optimal inheritance model was 2MG-EA, with a positive additive major gene effect and a major gene heritability as high as 98.79%. The petal count exhibited relatively high heritability and transmissibility, but with a negative heterosis (-27.57%). Most F1 individuals had fewer petals than the mid-parent value, and the double-petal phenotype was unstable. The adaptability test suggested the optimal inheritance model for petal count was 2MG-AD. The stamen and pistil count both showed substantial variation in the F1 generation, indicating the potential for genetic improvement. The stamen count exhibited strong positive heterosis, high-parent value, and high heritability. Its optimal model was 2MG-AD, with a positive additive effect (3.72) and a negative dominance effect (-2.45), indicating a degree of suppression from dominant genes. The major gene heritability was 92%, showing stable inheritance primarily under additive genetic control. The pistil count had a high coefficient of variation, heritability, and broad-sense heritability. The best model was 2MG-A, indicating the inheritance was dominated by additive effects, suggesting good selection potential. The peduncle length conformed to a normal distribution but had the highest coefficient of variation (417.24%), indicating strong phenotypic plasticity in response to environmental factors. It had relatively low transmissibility (20.5% ) and broad- sense heritability (52.75% ). The F1 mean value was slightly lower than the mid-parent value, showing negative heterosis. The optimal genetic model was 2MG-AD, but the additive and dominance effects of the major genes were weak.【Conclusion】The floral traits of the F1 progeny from the cross between Hongxun No. 1 and Double-flowering crabapple displayed varying degrees of genetic variation and segregation. The flower diameter and stamen count showed high heritability and stable major gene control, making them priority traits for selection and fixation. The petal count was governed by a complex genetic mechanism involving both major genes and dominant suppression effects. Thus, breeding for double flowers should involve double- flowered parents on both sides. The pistil count exhibited significant variation and was regulated by additive effects of major genes, showing the potential for improvement. The peduncle length demonstrated low heritability and selectability, indicating the need for comprehensive evaluation integrating phenotype and environmental response.This study clarified the inheritance patterns of floral quantitative traits in the F1 population from Hongxun No. 1 × Double-flowering crabapple and would provide theoretical support and reference models for future floral organ trait improvement and molecular-assisted breeding.