Pollen Tube Growth and Embryo Formation in <i>Kalanchoë blossfeldiana</i> × <i>K.</i> x <i>houghtonii</i> and <i>K. blossfeldiana</i> : Insights for Overcoming Hybridisation Challenges

The Kalanchoë genus contains many popular ornamental plant species, and interspecific hybridisation is key to introducing new hybrids with novel features. This study aimed to determine pivotal parameters, i.e., pollen viability, germination, and early embryo development in intersectional pollination of K. blossfeldiana × K. x houghtonii and self‐pollination of K. blossfeldiana . In both combinations, pollen tubes reached the ovary 24 h after pollination (HAP) and entered the ovule 48 HAP by penetrating the micropyle part. Furthermore, it was observed that the funiculus connecting the placenta and ovule started to disconnect at 48 HAP in both hybridisations. The number of pollen tubes moving from the style to the ovary was lower in self‐pollination of K. blossfeldiana . Moreover, zygotes formed at 4 days after pollination (DAP) in both intersectional and self‐pollination hybridisation, and embryos developed to globular and heart stages in intersectional pollination, while to the globular stage in self‐pollination at 10 DAP. Embryo development stages were observed normally in self‐pollination, whereas in intersectional pollination, embryo sac shrinkage was encountered in some ovules at 10 and 15 DAP, and no embryo was seen at 20 DAP. Embryo rescue with ovule culture is recommended to increase the success of this specific intersectional hybridisation.