PROPAGATION OF LIRIODENDRON HYBRIDS VIA SOMATIC EMBRYOGENESIS

Propagation of hybrids between the Chinese tuliptree (Liriodendron chi nense) and the North American yellow-poplar (Liriodendron tulipiferea) could be greatly accelerated with a highly productive somatic embryog enesis system. Flowers were collected from a single Chinese tuliptree and the anthers used for controlled pollinations of 4 yellow-poplar mo ther trees. Aggregates of samaras resulting from the pollinations were harvested 8 weeks post-pollination. Following surface disinfestation, samaras were dissected and embryos and endosperm were cultured togeth er on a semisolid induction medium containing 9.0 muM 2,4-dichlorophen oxyacetic acid and 1.1 muM benzyladenine. Following 2 - 3 months on in duction medium, an average of 15.6 percent of the explants produced ei ther somatic embryos or proembryogenic masses. Compared to pure yellow -poplar embryogenic cultures, putative hybrid cultures tended not to m aintain growth as proembryogenic masses while exposed to auxin, instea d proliferating via repetitive embryogenesis as globular-stage embryos . Four to six weeks following transfer of globular embryos to basal me dium, mature embryos were produced from the putative hybrid lines. Mat ure embryos germinated following transfer to basal medium lacking case in hydrolysate. Plantlets survived transfer to potting mix and acclima tization to greenhouse conditions. Verification of the hybrid nature o f the embryogenic lines and somatic embryo-derived plantlets was accom plished by Southern hybridization analysis with a species-specific DNA marker.