Somatic embryogenesis and plant regeneration of northern red oak (Quercus rubra L.)

A somatic embryogenesis protocol for plant regeneration of northern red oak (Quercus rubra) was established from immature cotyledon explants. Embryogenic callus cultures were induced on Murashige and Skoog medium (MS) containing 3% sucrose, 0.24% Phytagel (TM), and various concentrations of 2,4-dichlorophenoxyacetic acid (2,4-d) after 4 weeks of culture in darkness. A higher response (66%) of embryogenic callus was induced on 0.45 mu M 2,4-d. Higher numbers of globular- (31), heart- (17), torpedo- (12), and cotyledon-stage (8) embryos per explant were obtained by culturing embryogenic callus on MS with 3% sucrose, 0.24% Phytagel (TM), and devoid of growth regulators after 8 weeks culture in darkness. Continuous sub-culturing of embryogenic callus on medium containing 2,4-d yielded only compact callus. Desiccation of embryos for 3 days in darkness at 25 +/- A 2A degrees C followed by cold storage at 4A degrees C in darkness for 8 weeks favored embryo germination and development of plantlets. Cotyledon-stage embryos subjected to desiccation and chilling treatment cultured on MS with 3% sucrose, 0.24 Phytagel (TM), 0.44 mu M 6-benzylaminopurine (BA), and 0.29 mu M gibberellic acid germinated at a higher frequency (61%) than with 0.44 mu M BA alone and control cultures. Germinated plantlets developed a shoot and root, were acclimatized successfully, and maintained in a growth room for plantlet development.