Variations and heritability of phenotypic characters in the reblooming bearded iris (Iris germanica L.)

Abstract

• Longer leaves on non-blooming stems and less flowers on a scape may be two phenotypes for the rebloomers to support twice flowering. • FM1 ( Iris germanica ‘Cornhusker’) was the most ideal maternal parent. • FM2 × M2 ( I. germanica ‘Delta Lady’ × I. germanica ‘HD’) was the ideal cross combination with the reblooming rate being 16.67%. • Length of fall and scape height gained the largest broad-sense heritability (88.03%) and narrow-sense heritability (66.63%), respectively. • There were correlations between the vegetative trait plant height and the floral characters. The reblooming bearded iris ( Iris germanica L.) could bloom in not only spring, but also autumn. The additional blooming seasons bring the phenotypic differences between the once-bloomers and the rebloomers. However, the lack of studies on the rebloomers’ phenotypic variations largely hinders the process of breeding. In this study, ten F 1 populations were produced according to the North Carolina Design II, using five maternal and two paternal parents. After the hybridization, the leaves of non-blooming stems were longer than their parents in all of the F 1 populations, the photosynthesis of which may provide more nutrition for the additional blooming. Furthermore, the fewer flowers on a scape in F 1 could be another phenotype to support twice flowering. The six floral characters (height of individual flower (HF), diameter of flower (DF), length of fall (LF), width of fall (WF), length of standard (LS) and width of standard (WS)) were all largely improved in the cross combination of FM2 × M2 ( I. germanica ‘Delta Lady’ × I. germanica ‘HD’) over both parents. FM2 × M2 was considered as the ideal cross combination after the comprehensive analysis of heterobeltiosis, special combining ability and reblooming rate (16.67%). The general combining ability values showed that FM1 ( I. germanica ‘Cornhusker’) tended to be the ideal maternal parent. LF and scape height gained the largest broad-sense and narrow-sense heritability (88.03% and 66.63%), respectively. The correlations between the vegetative trait (plant height) and the six floral characters (HF, DF, LF, WF, LS and WS) enabled the selection of the large-flower individuals at the stage of vegetative growth. All these results presented a preliminary profile of the phenotypic characters inheritance, and may guide the future breeding of the rebloomers.