Abstract: 【Objective】 Inflorescence traits are an effective representation of ornamental merit in chrysanthemum. Heterosis and genetic analysis of inflorescence traits will provide an invaluable guidance for the breeding program of chrysanthemum with excellent ornamental traits. 【Method】 In this study, inheritance and heterosis analysis were carried out for 6 inflorescence traits of chrysanthemum based on phenotypic data in 2008-2009 of 142 F1 population derived from autumn-flowering chrysanthemum cultivar ‘Yuhualuoying’ with single flowers (female parent) and summer-flowering chrysanthemum cultivar ‘Aoyunhanxiao’ with double flowers (male parent) using single generation segregation analysis method of major gene plus polygene mixed genetic model. 【Result】 Compared with mid-parent value (MPV), the heterosis value of mid-parent (Hm) for the inflorescence traits of flower head diameter, ray floret number, ray floret length, ray floret width and center flower diameter, except tubular floret number, showed a significant difference degree at 0.01 level, and the ratio of heterosis value of mid-parents (RHm) for the first five traits were -3.19%, -25.17%, -4.46%, -12.81%, and 5.06%, respectively. The mixed genetic analysis revealed that there was no major gene detected for ray floret length and width, and flower diameter was fitting A-1 model with additive effect (0.618) larger than its dominant effect (0.168); ray floret number accorded with B-2 model with additive-dominant effect, additive effect of the first major gene (24.575) was larger than that of the second (13.120) and the dominant effect of the two was null; tubular floret number was fitting A-4 model with negatively complete dominant effect; center flower diameter were apt to B-3 model with additive effect. The heritability of major gene for the four inflorescence traits of flower diameter, ray floret number, tubular floret number and center flower diameter were 66.69%, 80.99%, 58.24% and 56.49%, respectively. 【Conclusion】 The heterosis and transgressive segregation of inflorescence traits commonly existed in F1 hybrid progenies of chrysanthemum and there were some dominant effect in the heterosis of flower diameter, ray floret number, ray floret length and width. Major genes with dominantly additive gene effects were detected for flower head diameter, ray floret number, tubular floret number and center flower diameter, and consequently, the detection of these major genes controlling inflorescence traits will afford a theoretical basis for the further study of QTL analysis and molecular marker assisted breeding program in chrysanthemum.

Key words: Chrysanthemum morifolium, inflorescence trait, heterosis, major gene plus polygene, genetic analysis