Embryogenic cell lines of Juniperus communis; easy establishment and embryo maturation, limited germination

Abstract

Several coniferous species belonging to the Pinaceae family can be propagated via somatic embryogenesis, while species belonging to the Cupressaceae family cannot. The aim of this study was to identify possibilities and limitations with somatic embryogenesis in Cupressaceae. Juniperus communis was chosen as model species. We show that a high initiation frequency of embryogenic cell lines can be established from intact megagametophytes at the time when intensive cleavage polyembryogeny takes place. The embryogenic cell lines proliferate fast on medium lacking plant growth regulators. Early somatic embryos develop after transfer to medium with decreased content of nitrogen and calcium. The early embryos mature after exposure to abscisic acid. Mature cotyledonary embryos germinate after partial desiccation. A high proportion, over 40%, of the germinating embryos retain the embryogenic potential in the basal part, resulting in development of new embryogenic tissue.

Recalcitrance in clonal propagation, in particular of conifers

“…An unusual feature of the L. decidua somatic embryos was that initially they were incapable of switching from the embryogenic to the vegetative mode, with new adventitious embryos forming from various parts of the primary and secondary ones before finally developing proper shoots (Bonga 1996). A similar mode-switch failure was observed in mature somatic embryos of J. communis in which the basal part remained embryonic (Helmersson and von Arnold 2009). The transition from embryonic to vegetative growth is an important one in the life cycle of the plant, and in the above cases, this transition appears to be delayed.…”

“…For several conifers, mature zygotic embryos are already non-responsive and immature embryos have to be used. For example, for Pinus banksiana and Juniperus communis (Helmersson and von Arnold 2009) only embryos at the polyembryonic cleavage stage will respond. The zygotic embryo in pine seeds cleaves at the 16-cell stage, forming four new embryos each composed of four cells (Fig.…”

Conifer somatic embryogenesis – an efficient plant regeneration system for theoretical studies and mass propagation

“…2a). Using megagametophytes with immature embryos as explants is advantageous owing to the Immature embryos enclosed in megagametophytes have been used as explants in several conifer species as Abies alba (Gajdošová et al 1995;Krajňáková et al 2013a), Abies nordmanniana (Nörgaard and Krogstrup 1991), Juniperus communis (Helmersson and von Arnold 2009), Taxus brevifolia and T. cuspidata (Ewald et al 1995) but are typical for the species of the genus Pinus, as Pinus sylvestris (Aronen et al 2009), Pinus radiata (Montalbán et al 2012;Hargreaves et al 2009), Pinus pinaster (Humanez et al 2012), Pinus nigra (Salajova and Salaj 1992), Pinus palustris (Jones and van Staden 1995), Pinus halepensis (Montalbán et al 2013) Pinus oocarpa (Lara-Chavez et al 2011). Immature zygotic embryos excised from megagametophytes have been used in Picea glauca and Picea mariana (Hakman and Fowke 1987), Picea abies (Nagmani et al 1987), Picea sitchensis (Krogstrup et al1988).…”

“…The initiation frequencies have been variable depending on the species, year of cones harvest, developmental stage of zygotic embryos, nutrient medium composition reaching values in average 20% for Pinus pinaster (Humanez et al 2012), 5-50% for Juniperus communis (Helmersson and von Arnold 2009), 5% for Pinus taeda (Becwar et al 1990), 2.1-10.3% for Pinus nigra Salaj et al (2014) and 20.6% for Pinus radiata (Montalbán et al 2012).…”

Micropropagation of Juniperus navicularis, an endemic and rare species from Portugal SW coast

“…To date, only two reports showed that it is possible to induce somatic embryogenesis in J. oxycedrus (Gómez and Segura 1995) and J. communis (Helmersson and von Arnold 2009). However, in neither species mature somatic embryos nor plants were obtained.…”