Variation and inheritance of the degree of style branching in hybrids of Iris dichotoma × I. domestica

Abstract

The degree of style branching is an important characteristic for classification, reproduction and ecological function in the Iridaceae family. We established 6 generations derived from Iris dichotoma and I. domestica, and calculated the style branch ratio (the ratio of each style branch to the whole style in length) to express the branching degree of style. The variation of style branch ratio was analyzed and the genetic mechanism of style branch ratio was explored by using the major gene plus polygene mixed inheritance analysis model. The style branch ratios of the progeny were between their parents, in which the style branch ratios of F1 (I. dichotoma × I. domestica) were intermediate between P1 (I. dichotoma) and P2 (I. domestica); BC1Dic (F1 × P1) and BC1Dom (F1 × P2) were close to their recurrent parents, respectively. F2 displayed a wide and continuous variation in the degree of style branching. E-1 (MX2-ADI-AD) was the optimal genetic model for the style branch ratio, indicating that it was controlled by two major genes with additive, dominant, and epistatic effects plus polygene with additive and dominant effects. In major genes, the unbranched was dominant, but in polygene the branched was dominant. The additive effect of polygene was the largest in all effects. The major gene heritabilities in BC1Dic, BC1Dom, and F2 were 32.76%, 39.81%, and 37.63%, respectively. The polygene heritability in BC1Dic, BC1Dom and F2 were 0%, 36.05% and 46.40%, respectively. Therefore, we obtained a good material with continuous variation in the degree of style branching for further research on its reproductive and ecological functions; our findings lay the foundation for QTL mapping to further study the genetic mechanism of the degree of style branching.