Plant regeneration through organogenesis from callus induced from mature zygotic embryos of loblolly pine

Mature zygotic embryos from three seed sources of loblolly pine were cultured on callus induction medium containing 10 mg l^-1 α-naphthaleneacetic acid, 4 mg l^-1 benzyladenine (BA), 400 mg l^-1 casein hydrolysate, and 400 mg l^-1 glutamine for 6 weeks. Light-yellow, loose, glossy, globular callus was formed, and the highest frequency was 35.7%. The highest differentiation frequency of callus on adventitious bud induction medium was 62.1%. After culture of calli with adventitious buds on elongation medium for 6 weeks, adventitious shoots more than 1.0 cm in height were selected for rooting. On rooting medium supplemented with 0.1 mg l^-1 indole-3-butyric acid, 1 mg l^-1 BA, and 0.5 mg l^-1 gibberellic acid, the highest rooting frequency of adventitious shoots was 46% in a culture period of 6 weeks. Established plants survived following transfer to soil at a frequency of 71%.