Influence of explant selection on the shoot-forming capacity of juvenile tissue of Pinusradiata

Abstract

The shoot-forming capacity of Pinusradiata D. Don juvenile explants under tissue culture conditions was examined. Three types of explant were used: whole embryos; cotyledons excised from whole embryos which had been cultured for 1 week on the shoot initiation medium; and cotyledons excised from 1-week-old aseptically germinated seeds. The average number of rootable shoots produced per seed in 12–13 weeks was 9 for excised embryos, 18 for their separated cotyledons, and 180 for the cotyledons from germinated seeds. Induction of a smooth-surfaced, yellow–green, nodular meristematic tissue appears to be a requirement for the formation of large numbers of adventitious shoots. By extending the culture period from 12 to 24 weeks more than 1300 shoots were formed from the cotyledons of one germinated seed. To date, no other conifer tissue culture method has been reported to give such a large number of adventitious shoots of the same clone in a first generation.