A comparison of BA, zeatin and thidiazuron for adventitious bud formation from Picea glauca embryos and epicotyl explants

Abstract

Picea glauca (white spruce) zygotic embryos and one-week-old-seedling epicotyl explants were placed on either Woody Plant Medium (WPM) or half-strength Schenk & Hildebrandt (1/2S&H) medium supplemented with varying levels of benzyladenine (BA) (0.1, 1.0, 10, 50, 100 μM), zeatin (10, 50, 100 μM) or thidiazuron (TDZ) (0.01, 0.1 μM). In addition to differences in the number of buds induced at three months on the two media, buds induced on WPM were visually more uniform, less vitrified and elongated faster. On 1/2S&H supplemented with BA, maximum bud induction from embryos occurred on 1.0 μM BA with 0.01 μM TDZ with higher BA concentrations inhibitory to bud induction. In contrast, on WPM there was little difference in the number of buds induced from embryos placed on 10, 50 and 100 μM BA with or without TDZ. One-week-old-seedling epicotyl explants required higher BA levels on 1/2S&H, as bud induction at three months was greatest at 10 μM BA. On WPM, as with the embryos, there were only minor differences in the number of buds induced from epicotyl explants on the various BA levels. Zeatin was more effective at inducing buds than BA with both media. From embryos, bud induction was greatest on 50 or 100 μM zeatin without TDZ and 50 or 100 μM zeatin with or without TDZ on 1/2S&H and WPM respectively. From epicotyl explants on 1/2S&H, there was little difference in the number of buds induced with the zeatin concentrations used, while with WPM, 50 and 100 μM zeatin induced the greatest number of buds. Interestingly, with BA, the epicotyl explants needed a higher level than the embryos for maximal response, while with zeatin, the level was the same for both embryos and epicotyl explants. Long-term (six month) survival was higher on WPM than with 1/2S&H. Additionally, embryos had a higher percentage of genotypes surviving at six-months when compared with epicotyl explants. For overall survival and development of the buds, 50 μM zeatin with 0.01 μM TDZ was the best treatment tested.