Cross Compatibility between Hydrangea serrata (Thunb.) Ser. and Hydrangea macrophylla (Thunb.) Ser., and Efficiency Improvement of Hybrid Acquisition with Ovule Culture

Abstract

Cross compatibility between Hydrangea serrata (Thunb.) Ser. and Hydrangea macrophylla (Thunb.) Ser., adequate conditions for ovule culture for their hybridization, and cross compatibility among hybrid individuals were examined. Seed formation did not occur in hybridization between H. serrata and H. macrophylla when H. serrata was used as the seed parent; however, a high rate of seed formation was confirmed using H. macrophylla as the seed parent. Individual hybrids could be acquired with ovule culture for most cross combinations between cultivars of H. serrata and those of H. macrophylla. To efficiently acquire hybrid individuals by interspecific crossing with ovule culture, the culturing ovules had to be passed 60 days after crossing and cultured in 1/2 MS (made by Murashige and Skoog) medium with the addition of gibberellin (GA₃) 1 mg·L⁻¹. Individual hybrids were acquired with ovule culture in all cross combinations when hybrid plants between H. serrata and H. macrophylla were crossed with cultivars of H. macrophylla or those of H. serrata.