The principal aim of this investigation was to improve somatic embryogenesis initiation and to enhance representation of families and genotypes within those families of Pinus radiata D. Don. A total of 19 open-pollinated seed families, many with unrelated and weakly related parents, were tested. Optimum stage of cone maturity for initiation success was tested by five collections made at 1 week intervals, spanning the developmental period from pro-embryo to cotyledonary embryos. Two media were compared; embryo-development media (EDM6) and a modified Litvay medium (Glitz). Two zygotic embryo explant-preparation techniques were tested; embryos with retained megagametophytes and excised embryos. Proliferating embryogenic tissues were obtained from all four treatments (2850 explants per treatment, 570 per collection time) for the 19 families. The best initiation rates were achieved with a combination of Glitz medium with excised zygotic embryos, with 55% of explants from all collections and all families combined giving rise to proliferating embryogenic tissue. At the optimal collection time for each of the families, this treatment gave a range of 47%–97% initiation success with an average of 70% per family.

This is the first published report comparing production and performance of adventitious shoots from cryopreserved cotyledons, with axillary shoots formed from epicotyls of the same zygotic embryo of radiata pine (Pinus radiata D. Don). Genotypes from 10 control-pollinated families of P. radiata in two treatments were compared for shoot initiation, in vitro growth, rooting, and early nursery performance. Plant growth in nursery beds was assessed by measuring height after 2 and 7 months. After 8 months in nursery beds, the physiological ages of genotypes were assessed before field planting. Genotype capture was higher from the cryopreserved cotyledons than from the epicotyls. This technique has the advantage of preserving juvenile material while field testing is done. Early shoot multiplication in both treatments was good. After four transfer cycles, epicotyl cultures showed improved elongation and higher multiplication rates. After 6 months of in vitro growth, shoots from both treatments were given auxin pulses. Shoots of adventitious origin were slower to root than epicotyl-derived shoots. Overall rooting rates were satisfactory. Plants of adventitious origin were shorter when planted into nursery beds and when transferred to field trials. Assessment of relative physiological age indicated that all plants of adventitious origin showed some increase.