Effect of basal medium, growth regulators and Phytagel concentration on initiation of embryogenic cultures from immature zygotic embryos of loblolly pine (Pinus taeda L.)

Low initiation frequency is one of the main barriers in applying somatic embryogenesis to the clonal production of Pinus species. Factors affecting initiation, including basal medium, plant growth regulators, and Phytagel concentration, have been investigated in loblolly pine (Pinus taeda L.). BM1 basal medium proved superior to DCR1 and LP (LP basal salts plus BM1 organic nutrients). No extrusion from megagametophytes was exhibited on LP medium. The combination of 3 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.5 mg/l 6-benzylaminopurine (BA) resulted in a higher extrusion frequency than that of 11 mg/l 2,4-D, 4.5 mg/l BA and 4.3 mg/l kinetin. Phytagel at 1 g/l resulted in the highest explant browning, but the lowest extrusion frequency, while 4 g/l Phytagel induced some dry embryogenic extrusions. Phytagel at 2 g/l was regarded as the best level for initiation of embryogenic cultures.