Comparative in vitro and early nursery performance of adventitious shoots from cryopreserved cotyledons and axillary shoots from epicotyls of the same zygotic embryo of control-pollinated Pinus radiata

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.