Immature Embryo Culture of Hydrangea quercifoia Bartr

Hydrangea quercifolia Bartr. is one of the most beautiful native shrubs in the United States for its great foliage color and exfoliating bark. To cross it with other Hydrangea species, embryo rescue is needed to avoid embryo abortion during maturation. Immature embryo was excised and sterilized at 75% alcohol for 5, 10, 15, and 20 seconds. As exposure times went up, the embryo germination rate decreased from 18.5 to 3.7%. Media were optimized within 4 formulations and the B-5 media produced highest embryo germination rate at 18.5%, which was significantly higher than that of WPM and MS (full or half strength). Sucrose concentrations had significantly affected on embryo germination rate and media with 2% sucrose yielded 18.5% germination rate. Both increasing and decreasing sucrose concentrations greatly reduced the embryo germination. The optimization of H. querifolia immature embryo germination system should be sterilized immature embryo at 75% alcohol in 5 seconds or less, then cultured them in B-5 media with 2% sucrose. Further studies should focus on improving immature embryo germination rate and its micropropagation.