Cross-compatibility in Interspecific Hybridization of Lychnis (Caryophyllaceae) and Characterization of Interspecific Hybrids between L. fulgens and L. sieboldii

Lychnis belongs to Caryophyllaceae and contains a number of horticulturally attractive species. In order to widen their variations in horticultural traits, interspecific cross-pollination and subsequent immature seed culture were carried out using 8 Lychnis species, L. chalcedonica, L. coronata, L. fulgens, L. gracillima, L. kiusiana, L. miqueliana, L. sieboldii, and L. wilfordii. Enlarged fruits containing immature seeds were obtained in the 26 cross-combinations 4 weeks after pollination. Immature seeds were isolated from the fruits and cultured on halfstrength Murashige and Skoog medium without plant growth regulators, on which germination occurred in 11 cross-combinations and seedlings were produced in 8 cross-combinations. However, green seedlings were obtained only in L. fulgens × L. sieboldii, and seedlings obtained from the other 7 cross-combinations, L. coronata × L. gracillima, L. gracillima × L. coronata, L. kiusiana × L. fulgens, L. kiusiana × L. sieboldii, L. kiusiana × L. wilfordii, L. wilfordii × L. kiusiana, and L. wilfordii × L. sieboldii, were albino and died during acclimatization. The hybridity of all 55 green seedlings obtained from L. fulgens × L. sieboldii was confirmed by random amplified polymorphic DNA analysis. Although some morphological variations were observed among hybrids, hybrid plants generally showed intermediate morphologies between the parents. Hybrids showed high pollen fertility and their selfpollination yielded viable seeds. The present study shows the possibility of interspecific cross-breeding in Lychnis. Further studies are necessary to improve the culture conditions of immature seeds and to examine interspecific cross-compatibility using a wide range of Lychnis species.