Abstract
Somatic embryogenesis was studied in four spruce species (<em>Picea abies</em>, <em>P. omorika</em>, <em>P. pungens</em> 'Glauca' and <em>P. brewenana</em>) to determine if this method can be used for in vitro propagation of coniferous trees. The highest frequency of initiation of embryogenic tissue was obtained when mature zygotic embryos were used as explants. It ranged then from 10.8% (<em>P. brewenana</em>) to 23.75% (<em>P. omorika</em> and <em>P. pungens</em> 'Glauca'). The frequency of embryogenic tissue initiation was strongly affected by medium composition, i.e. addition of appropriate auxins (2,4-D, NAA, Picloram) and sucrose concentration (10-20 g<sup>-1</sup>"1). A lower frequency was obtained in <em>Picea omorika</em> (10%) when megagametophytes (endosperms with immature zygotic embryos) were used as explants. No emryogenic tissue was produced from hypocotyls, cotyledons and needles. A satisfactory frequency was achieved with the use of somatic embryos of <em>Picea abies</em> (30%). The proliferation of embryogenic cell lines of spruces was affected by medium type. The experiments resulted in production of somatic plantlets of <em>P. abies</em> and <em>P. omorika</em>. This enables the application of this method of spruce micropropagation for genetic and breeding research or for nursery production.
Highlights
In spite of numerous studies on somatic embryogenesis, conducted in recent years in various laboratories all over the world, it is still not easy to produce somatic embryos in vitro, especially in coniferous tree species
In this study we aimed to develop a method for regeneration of somatic embryos of four spruce species (Picea abies, P. omorika, P. pungens Glauca and P. breweriana) from embryogenic tissues induced from various explants
The highest frequency of embryogenic tissue initiation for P. abies was recorded in media with lowered concentrations of macro and/or micronutrients (1/2 LM and 1/2 macro LM), while for P. breweriana in 1/2 macro LM (Table 2)
Summary
In spite of numerous studies on somatic embryogenesis, conducted in recent years in various laboratories all over the world, it is still not easy to produce somatic embryos in vitro, especially in coniferous tree species. Micropropagation by means of somatic embryogenesis is very beneficial, mainly due to the high regeneration rate and possibility to produce, within a short period, an unlimited number of plantlets from a small amount of initial material (Gupta et al 1993). This method is attractive because the process of somatic embryo production can be automated, thanks to the use of bioreactors, which may substantially reduce the cost of the produced plants (Ibaraki and Kurata 2001; Jain and Ishii 2003). Capable of further development into normal plants, were first produced independently by Chalupa (1985) as well as Hakman and von Arnold (1985), from embryogenic tissues initiated from immature zygotic embryos of Picea abies
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