Abstract
Conventional breeding within natural cross border frames is not always
sufficient to increase genetic variability and produce new characteristics such as leaf and flower shape or cold tolerance. Interspecific hybridisation is an approach to obtain new plants with desired features. However, hybridization between plant species is associated with many challenges to enable survival of the developing embryo. Here we present an optimised technique for embryo rescue via ovule isolation in selected intra- and interspecific Campanula hybrids. A frequent problem in embryo rescue is the malformation of the endosperm. To circumvent this, embryos were isolated and the optimal ovule isolation time and growth conditions were determined to increase embryo survival. Ovules were isolated one to four weeks after pollination and cultivated on a modified MS medium. When ovules were allowed to stay inside the ovary for 2-3 weeks the number of germinating embryos increased as compared to ovules isolated one week after pollination. Additionally, ovules isolated 2-3 weeks after pollination showed an increased embryo germination rate. Among the Campanula hybrids, produced here from both the intraspecific crosses within C. carpatica ‘White’ and the interspecific crosses between C. medium
and C. formanekiana, the timing of ovule isolation time was critical. This study in Campanula supports that ovule isolation time is an important parameter in embryo rescue techniques affecting both the number of germinating embryos and the rate of their germination.