Seasonal variation of sepal-petaloidy in F₁ progenies of double-flowered cyclamen

Cyclamen persicum is popular as a potted flower and its cold tolerant cultivars are used as garden plants. Recently, new double-flowered cyclamen cultivars with petaloid stamens or sepals have been bred by crossing. Our previous studies revealed that constant low and medium growth temperatures promoted the petaloidy of stamens. However, the effects of seasonal environmental changes, such as those associated with growth temperature and light conditions, on sepal-petaloidy of F₁ progenies was not assessed under actual cultivation conditions. Therefore, the seasonal variation of sepal-petaloidy in F₁ progenies of double-flowered cyclamen was investigated in this study. F₁ progenies produced by reciprocal crossing between single- and double-flowered cyclamens with petaloid-sepals were used. The seedlings obtained from eight cross combinations were cultivated using common methods under glasshouse conditions, from February to April 2019, during the flowering in each flower and within each plant. Degree of petaloidy, according to the sepal shape in each flower, was categorized into four levels. Additionally, a petaloidy index (PI) of each plant was calculated using the degree of petaloidy and the number of flowers. Based on the floral phenotypes of F₁ progenies, it was suggested that the double-flower trait was dominantly inherited. In double-flowered progenies, the degree of petaloidy showed variation where most of the flowers that opened in the early season expressed a lower degree of petaloidy than those flowers opened in the late season. The seasonal changes of petaloidy in F₁ progenies were expressed regardless of the cross combinations. However, the degree of petaloidy in several F₁ plants did not show significant seasonal differences between flowers in February and April during the flowering season. These results indicate that seasonal changes of petaloidy were regulated both by environmental and genetic factors.