Co-expression of Long-lasting and Hose-in-hose Flower Traits in Evergreen Azalea

Abstract

The long-lasting flower (sepaloid corolla) traits, known as “misome-shō” and hose-in-hose flower (petaloid sepal) traits, that exist in Japanese azalea cultivars are homeotic mutations caused by transposable mutations of MADS-box B class genes AP3 (ap3／ap3) and PI (PI-H／PI). DNA markers have been developed to detect each gene mutation. In this study, the possible co-expression of long-lasting and hose-in-hose flower traits controlled by B class gene mutations was evaluated based on floral characteristics in crossed progenies that were selected by DNA markers. In crossed progenies involving the F₁ hybrid of long-lasting flower cultivars and hose-in-hose cultivars as breeding parents, although individuals with both the PI-H mutant allele and ap3／ap3 mutant allele were predicted to appear in long-lasting flowers with petaloid sepals, all showed long-lasting flowers with non-petaloid sepals. In some of these individuals, the sepals were the same color and the petals and their adaxial epidermal cells were larger than those of normal sepals and similar to those of petals. Individuals with the PI-H mutant allele showed female sterility. These results indicate that it is difficult to produce individuals that co-express long-lasting and hose-in-hose flower traits controlled by MADS-box B class genes.