Initiation of embryogenic cultures and somatic embryo development in loblolly pine (Pinustaeda)

Abstract

Immature zygotic embryo explants (isolated or with intact megagametophytes) from 10 loblolly pine (Pinustaeda L.) clones (7-34, 7-56, 11-9, 11-16, 11-25, 10-1003, 10-1007, 10-1011, 10-1018, and 10-1019) were surveyed for their potential to form embryogenic tissue from the suspensor region of zygotic embryos. After over 14 000 explants were cultured, embryogenic cultures were initiated from explants of 8 of the 10 clones; only explants from clones 11-25 and 10-1019 were not responsive. Embryogenic tissue was initiated from zygotic embryos with intact megagametophytes on MSG basal medium with no exogenous plant growth regulators or with 2–5 mg/L 2,4-dichlorophenoxy acetic acid (2,4-D) and 0–1 mg/L N6-benzyladenine (BA). The highest initiation frequency (5%) was obtained from isolated zygotic embryos of clone 7-34 less than 0.5 mm in length just prior to cotyledon primordia development on DCR basal medium with 3 mg/L 2,4-D and 0.5 mg/L BA. Two types of embryogenic cultures were maintained on medium with 2,4-D and BA: (i) those that contained pre-embryonal masses of cells interspersed with unaggregated suspensorlike cells, but which rarely contained well-formed somatic embryos, and (ii) those that frequently contained well-formed somatic embryos. Somatic embryo development from both types of cultures progressed to a precotyledonary stage on medium with 2.6 mg/L abscisic acid.

Difference in the Ability of Initiation and Maintenance of Embryogenic Cultures among Sugi (Cryptomeriajaponica D. Don) Seed Families.

“…The overall mean rate was 45.6% (689/1512). This is higher than that found for immature zygotic embryos of Pinus species (for example, 1.4% for 10 seed families of P. taeda, Becwar et al, 1990, and 15.3% for 13 seed families of P. strobus, Garin et al, Table 1. Embryogenic response of 20 open-pollinated seed families using zygotic immature embryo explants of C. japonica.…”

Somatic embryogenesis in loblolly pine (Pinus taeda L.): improving culture initiation rates

“…Reports on initiation of LP embryogenic tissue indicate initiation frequencies of 1-5% [1,3,8,12,13]. Several patents contain methods for improved initiation frequencies for LP [2,10,11].…”

Embryogenic Cell Culture, Protoplast Regeneration, Cryopreservation, Biolistic Gene Transfer and Plant Regeneration in Japanese Cedar (Cryptomeria japonica D. Don).

“…The optimal developmental stage of zygotic embryos as a critical factor in somatic embyogenesis initiation for several conifer species has been reported in terms of seed collection date or time after fertilization (Becwar et al, 1990;Tautorus et al, 1991;Lelu et al, 1994;Jamn et al, 1995;Lelu et al, 1999;Kim et al, 1999). However, due to the difficulty of determining the precise time of fertilization in openpollinated cones and that variation in zygotic embryo development depends on weather and location, the criteria of explant collection for embryogenic cell induction cannot be easily generalized.…”