Application of Somatic Embryogenesis to Clonal Propagation of Interior Spruce
Seventy one lines (genotypes) of embryogenic cultures from six open pollinated families were obtained by culturing immature embryos of interior spruce. Induction frequencies varied among families and was also affected by cone collection date. Comparison of the SDS-PAGE protein profiles of embryo expiants from different collection dates revealed that embryos were most competent for embryogenesis during the period of development that directly preceded significant accumulation of storage protein. In order to optimize the maturation protocol, cultures from each genotype were screened through a range of abscisic acid (ABA) concentrations. The ABA-dependent developmental profile (the proportion of shooty embryos, precociously germinating embryos and mature embryos) differed among genotypes but, in general, production of somatic embryos was highest at 40 and 60 μM ABA. At these concentrations of ABA, embryos from most genotypes did not germinate precociously and entered a period of quiescence. Germination of eight genotypes tested was markedly enhanced after partial drying of mature embryos at high relative humidity. After one week, root emergence averaged 67% for somatic embryos treated with partial drying compared with 0% for non-treated controls. Emblings derived from this method were vigorous and acclimatized well to soil. Survival of emblings following transfer to soil, acclimatization and the first season’s growth in the nursery was 80% or greater for most genotypes and averaged 83% overall. Growth of emblings during the first season averaged 8.5 cm and was equivalent to that of seedlings.
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