Production of vigorous, desiccation tolerant white spruce (Picea glauca [Moench.] Voss.) synthetic seeds in a bioreactor

Abstract

This report describes a low-cost method for generating large numbers of high quality mature white spruce (Picea glauca [Moench.] Voss) somatic embryos which survived desiccation and grew to plantlets more vigorously than excised zygotic embryos cultured in vitro. Somatic embryos from suspension culture were supported within a culture chamber on a flat absorbent pad above the surface of a liquid culture medium containing 20-50 μM abscisic acid and 7.5 % polyethylene glycol. Throughout a 7 week culture period 3 L of fresh medium was pumped into one end of the chamber, while the spent medium exited by gravity from the opposite end. Over 6,300 cotyledonary stage white spruce somatic embryos were recovered after this time from a single culture chamber without manual manipulation. The somatic embryos were of excellent appearance with well developed cotyledons, and possessed high levels of storage lipids. They survived drying to about 8 % moisture content following treatment for 4 weeks at 63 % relative humidity, and following imbibition converted to normal plantlets at a frequency of 92 %, compared to 80 % for embryos grown in Petri dishes. Somatic embryos cultured within the bioreactor developed to plantlets that were 20 % longer than zygotic embryos excised from mature seed and grown in vitro, and were 38 % longer than somatic embryos cultured upon agar medium in Petri dishes.