The major gene and polygene effects of ornamental traits in bearded iris (Iris germanica) using joint segregation analysis

Abstract Bearded iris (Iris germanica) is an indispensable horticultural perennial in the garden of spring. Therefore, improving their ornamental value is of great importance in the process of breeding. In order to find out whether the inheritance of some ornamental characters in bearded iris was controlled by major genes or polygenes, the joint segregation analysis was applied to investigate the inheritance of the six characters related to ornamental values in six generations (P1, P2, F1, F2, BC1P1 and BC1P2), including plant height (PH), leaf length (LL), height of individual flower (HF), diameter of flower (DF), length of fall (LF) and width of fall (WF). The six tested characters performed large range of coefficient of variation in the offspring generations, from 8.11% to 16.48%, indicating the diversity of offspring’s phenotypic performances. The broad-sense heritability ranged from 4.55% (DF) to 51.19% (LF), suggesting the different ability to pass down these characters to the next generation. From the analysis follows the corollary that PH, HF and DF were all in accordance with the additive-dominance-epistasis major gene plus additive-dominance polygene genetic model (E-1). The optimum model for LL was the additive major gene plus additive-dominance polygene genetic model (E-3), while an additive-dominance major gene plus additive-dominance-epistasis polygene genetic model (D-0) was suitable for WF. Unlike the other five characters, LF accorded with the B-1 model, which was controlled by two major genes without polygene effect. It proved that the selection of LL and WF was more effective in early generations, while the selection of PH and DF would be more useful in late generations. This research shed some light on the inheritance pattern of ornamental characters in bearded iris, and laid solid foundation for further molecular breeding of ornamental plants.