Medium composition, developmental temperature, and pollen density enhanced in vitro pollen germination in Phalaenopsis

In vitro pollen germination is a fundamental tool for assessing the viability of the parental lines in breeding. The conditions for in vitro germination require consistent improvement to ensure correlation with actual in vivo germination performance. However , research on the in vitro germination of Phalaenopsis pollen remains limited. This study investigated the effects of modifying the germination media, pollinia developmental temperature, and pollen population size on pollen germination. Compared with the standard Brewbaker and Kwack (BK) medium containing 100 mg·L⁻¹ H 3 BO 3 and 300 mg·L⁻¹ Ca(NO 3 ) 2 ·4H 2 O, the modified BK medium supplemented with 125 mg·L⁻¹ H 3 BO 3 and 100 mg·L⁻¹ Ca(NO 3 ) 2 ·4H 2 O significantly enhanced pollen germination, increasing rates from 29.4% to 51.8% in Phalaenopsis Hualien Pink Apple ‘Hualien No 1-Pink Apple’ and from 16.8% to 26.4% in Phalaenopsis Sogo Yukidian ‘V3’. Furthermore, extending the cooling period until pollinia development is critical for achieving high pollen viability. An extended period of cooler developmental temperature (21/17 °C day/night from 94 to 121 days) enhanced pollen viability, with germination rates improving by 45.4% and pollen tube length increasing. Notably, this study demonstrates a pollen population effect in Phalaenopsis Hualien Pink Apple ‘Hualien No 1-Pink Apple’, where increased pollen density promotes both germination and tube growth. These findings provide essential guidance for Phalaenopsis breeding programs, offering a potential framework to improve cross-pollination efficiency and reproductive success in commercial orchid production.