Clonal Selection: The starting point for SE commercial production is the clonal establishment phase. The specific design of a clonal selection program depends on the pedigreed families available, level of gain expected and identification of target traits. Efforts on interior spruce are an example. In its conception, the program was designed to establish 1,000 clonal lines via SE using 30 to 40 top ranked families11. These families had been selected from 173 plus-trees based on 10 and 15-year progeny trial data for weevil-resistance and height, respectively. Subsequent execution of this plan resulted in the delivery of more than 1,300 lines from 36 top-ranked families to clonal trials from 1996 to 199812. The deployment strategy included the establishment of 6 to 8 copies on each of 3 or more sites selected for yield and high weevil-hazard. Prior to this program, approximately 250 lines from families varying in rank had been installed in trials during 1994 to 1995. Initial selection of 30 to 50 operational lines expected to begin in 1999, was based on a selection intensity of 5%20. Using a ‘Best’ family approach, a first-generation population of was constructed in 1997 (i.e., 5 lines × 12 top families)11. This was estimated to provide 60 % gain in weevil-resistance and 11 % gain in height over the baseline population. Gains after clonal selection, by definition are expected to be substantially higher; it has been calculated that these can be 40 to 60% as compared to 13% for seed orchards (El-Kassaby and Sutton, unpublished).

The steps of clonal selection include line initiation (induction), cryopreservation and production of plants for clonal trials. Typically, embryogenic cultures are established from excised embryo (i.e., spruce) and immature seed (i.e., pines and Douglas-fir) explants, with 200 to 2000 seed cultured per family. For large projects, seed volumes of 20 to 24 K may be handled in a 3 to 6 week window. Establishment of lines generally occurs within 1 to 8 weeks, with cryopreservation completed in 3 to 6 months. Production of plants (e.g., 10 to 200 copies per line) are delivered to the customer at 12-18 months; the timing of the delivery varies according to the species, region, trial schedule and the product format. For interior spruce, in vitro plants were delivered to the nursery within 9 to 10 months of receipt of the donor seed. Clonal trials were installed 13 to 14 months thereafter. In this program, close to 95% of the cryopreserved lines produced embryos and 80% of these met target numbers and stock quality for field trials.

CellFor Inc. and its predecessor companies have conducted clonal selection programs since 1990. Much of the current focus is on the development of programs for species with shorter rotation ages and advanced breeding, and in regions where plantation forestry is part of the forest estate. To date, greater than 3,000 clonal lines from 7 species have been placed in trials