© 2003 Heron Publishing—Victoria, Canada
Early selection improves clonal performance and reduces intraclonal variation of Norway spruce plants propagated by somatic
embryogenesis
Karl-Anders Högberg (1, 2), Peter V. Bozhkov (3) and Sara Von Arnold (3)
1. The Forestry Research Institute of Sweden, Ekebo, SE-268 90 Svalöv, Sweden / 2. Author to whom correspondence should be addressed (karl-anders.hogberg@skogforsk.se) / 3. Department of Forest Genetics, Swedish University of Agricultural Sciences, Box 7027, SE-750 07 Uppsala, Sweden / Received June 5, 2002; accepted August 25, 2002; published online January 31, 2003
Summary
Height growth during the first and second growth periods (i.e., the June–September period in consecutive years) and intraclonal
variation were assessed in 13 Norway spruce (Picea abies (L.) Karst.) clones propagated by somatic embryogenesis. The plants were acclimatized and grown in a greenhouse until mid-July
and then transferred outdoors. The clonal mean heights after the first and second growth periods were lower for somatic embryo
plants than for seedlings from corresponding families sown at the time of somatic embryo plant ex vitro transfer, because
a large proportion of somatic embryo plants were small. We determined whether certain selection criteria at ex vitro transfer
can be used to identify somatic embryo plants with height growth characteristics comparable with those of seedlings. Epicotyl
length and presence of lateral roots proved to be important parameters for selection, whereas main root length was less useful.
A combined selection for somatic embryo plants with lateral roots and with an epicotyl length exceeding 8 mm resulted in
taller plants and reduced intraclonal variation after the first and second growth periods. The growth of somatic embryo plants
selected in this way was similar to that of seedlings from the corresponding families. We conclude that selection according
to these criteria at ex vitro transfer can result in improved performance of clonal stock propagated by somatic embryogenesis.
Keywords:
epicotyl length, height growth, lateral roots, Picea abies.
