Two alternative pathways of somatic embryo origin from polyembryonic mature stored seeds of Pinus koraiensis Sieb et Zucc.

Abstract

Individual mature stored seeds of Pinus koraiensis sometimes contain several viable zygotic embryos originated through the processes of simple and cleavage polyembryony. To induce the embryonic process, isolated zygotic embryos were cultured on five different media all supplemented with 10 μM 2,4-dichlorophenoxyacetic acid and 5 μM 6-benzyladenine. Two alternative pathways of somatic embryo origin were revealed. The first pathway was associated with the production of a friable, translucent callus in the hypocotyls–cotyledon region of the dominant zygotic embryo. The second pathway was related to the proliferation of a translucent, moist, and mucilaginous tissue (termed embryonal–suspensor mass) in the suspensor region of the dominant zygotic embryo. Both types of tissues contained early somatic embryos. Regression analysis has shown a strong negative correlation between the frequencies of formation of embryogenic callus and embryonal–suspensor mass both at 3 and 8 weeks of culture (r = − 0.85; p = 0.07 and r = −0.71; p = 0.17, respectively). Key words: Pinus koraiensis; polyembryonal seeds; somatic embryogenesis; embryogénie callus; embryonal–suspensor mass.

Programmed cell death eliminates all but one embryo in a polyembryonic plant seed

“…We defined a 3-week period (between 8 and 11 waf) during which about 80% of the ovules were completely cleared of subordinate embryos, thus becoming monoembryonic. The clearance of remaining polyembryonic ovules (about 20%, most of which tended to contain subordinate embryos of greater size) was slow and asynchronous, sometimes being delayed until seed germination (data not shown, see also refs 5,8 ).…”

“…The pathway`all but one embryo die' described in the present study does not, however, seem to be an absolute rule for development of polyembryonic pine seeds. Certain conditions, including growth in arctic regions 5,7 and the presence of massive female gametophyte, 8 can allow complete development of more than one embryo in a single pine seed, indicating a high level of plasticity in the activation of embryo autodestruct mechanism.…”

Somatic embryo production and plant regeneration of Japanese black pine (Pinus thunbergii)

“…This has been reported in numerous pine species, including Pinus caribaea (Lainé and David 1990), Pinus elliottii (Newton et al 1995), Pinus lambertiana (Gupta and Durzan 1986), Pinus nigra (Salajova et al 1995), Pinus palustris (Nagmani et al 1993), Pinus patula (Jones and van Staden 1995), Pinus pinaster (Bercetche and Pâques 1995), Pinus radiata (Chandler and Young 1995), Pinus strobus (Finer et al 1989), Pinus sylvestris (Keinonen-Mettälä et al 1996), Pinus taeda (Becwar et al 1990), and Pinus koraiensis (Bozhkov et al 1997). Nevertheless, in most cases, the maturation of large numbers of somatic embryos and their conversion into plants has not been efficient.…”

Clonal variation in Scots pine (Pinus sylvestris) and in transgenic silver birch (Betula pendula)

“…Pine somatic embryogenesis (SE) has been induced using protoplasts of proembryonal cells (Gupta and Durzan 1987), immature (Becwar et al 1988, Jain et al 1989, Lainé and David 1990, Bercetche and Pâques 1995, Arya et al 2000 and mature zygotic embryos (Gupta and Durzan 1986, Hohtola 1995, Bozhkov et al 1997. Also, either dissected (Arya et al 2000) or whole (Lainé and David 1990, Nagmani et al 1993, Keinonen-Mettälä et al 1996 female gametophytes (megagametophytes) have been used for tissue culture initiation.…”