Adventitious shoot formation from embryonic explants of red pine (Pinus resinosa)

Adventitious shoots were induced from excised embryos of Pinus resinosa Ait, on half‐strength Le‐Poivre (LP) medium containing 1–70 μMN⁶‐benzyladenine (BA). At lower concentrations of BA, only 2–3 shoot primordia (from as many as 22 formed per embryo) developed into shoots when subcultured onto medium containing 0.5% activated charcoal. Concentrations of 10 to 70 μM of BA produced significantly higher numbers of shoot primordia and most of them developed into shoots. Ten to 17 day culture on medium containing 10–25 μM BA proved optimal for maximum adventitious shoot production. Less than three days of incubation on the cytokinin medium did not stimulate the formation of adventitious shoots. Twenty‐four day culture on the same medium produced several shoots, but most of them failed to develop normally and formed callus. Coconut milk (0.1–5% v/v) inhibited adventitious shoot formation. Using optimal conditions, seeds from 11 open‐pollinated selected trees were compared to test for genetic differences in the potential to produce adventitious shoots from embryos. No significant differences were observed with regard to the shoots produced per embryo among the different seed collections. More than 200 plants produced through this technique were tested for variation in several isozymes by electrophoresis. No variations were observed.