Protoplast Viabilty in the Lilacs and Prospects for Cell Manipulation

Few other woody plants embody the preeminence of temperate woody plants in garden cultivation like the lilacs. In spite of their relationship, the trees lack the diversity of cultivated floral forms observed within the shrub lineages. Typical selection and cross-pollination schemes within the tree lilacs have revealed few inherent variations for flower color throughout the long history of cultivation. Interspecies crosses have repeatedly failed between the two groups. Somatic hybridization is an in vitro technique in plant improvement that has demonstrated the ability to overcome the barriers of sexual incompatibility across species and familial divides. With Citrus spp. somatic fusion as a guideline for Syringa spp. protoplast isolation and culture, experiments were designed to optimize the conditions for somatic fusion. Protoplast isolation experiments examined various enzyme concentrations, formulations, and durations of exposure on protoplast liberation and viability. Leaf tissues from in vitro grown plants representing the taxonomic Subgenus Syringa series Syringa (Syringa xchinensis) and series Villosae (Syringa x ‘Dancing Druid’) were used as source material for those experiments. Digestion solutions were assessed for viability with fluorescein diacetate (FDA). Protoplast isolation experiments revealed significant increases in protoplast yield with the use of Driselase^® from Basidiomycetes sp. (P > 0.01) for any duration of exposure. Treatments containing pectinase and hemicellulase extracts from Rhizopus sp. (Macerozyme R-10) had a dramatic increase in protoplast yield over those treatments only containing hemicellulases derived from Aspergillus niger (P > 0.01). Protoplast isolation increased with increasing exposure to most digestion solutions, but came with an increased incidence of cell lysis or spontaneous fusion. Early indications envisage a difference in protoplast viability based on leaf anatomy. These differences may provide a convenient means for flow assisted cell sorting into groups that are more or less fit for regeneration and/or other techniques in plant protoplast manipulation.