RESUMEN
Somatic embryogenesis (SE), a clonal propagation method utilizing somatic cells, occurs under conditions that activate plant stress adaptation mechanisms such as production of protective secondary metabolites. Surprisingly, possible differences in susceptibility to insect pests between SE-generated and conventionally cultivated plants have not been previously explored. Here, we recorded frequencies and levels of bark-feeding damage by pine weevils (Hylobius abietis) in two large field trials, consisting of emblings (SE-propagated plants) and seedlings from 50 half-sib Norway spruce (Picea abies) families. We found that emblings were less frequently attacked by pine weevils, and when attacked, they were damaged to a lesser extent than seedlings. Moreover, we detected significant additive genetic variation in damage levels received by plants, indicating a heritable component to differences in resistance to insect herbivory among half-sib families. We present first-time evidence that emblings can be more resistant than seedlings to herbivorous insect damage, thus, SE appears to confer a previously unknown plant protection advantage. This finding indicates novel avenues to explore mechanisms underlying plant resistance and new approaches to develop non-toxic measures against insect pests.
RESUMEN
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.
Asunto(s)
Picea/crecimiento & desarrollo , Árboles/crecimiento & desarrollo , Clonación de Organismos , Raíces de Plantas/crecimiento & desarrollo , Tallos de la Planta/crecimiento & desarrollo , Plantones/crecimiento & desarrolloRESUMEN
A mixture of tritiated and deuterated gibberellin A(4) (GA(4)) was injected into the xylem of Norway spruce (Picea abies (L.) Karst) propagules, below an elongating shoot, or applied directly on the needles of an elongating shoot. The distribution of [(2)H(2)]GA(4) and [(3)H]GA(4) in the needles, stems and buds was determined after 4, 12 and 24 h. After 4 h, most of the xylem-injected GA(4) was found in the needles, whereas after 24 h, most of the GA(4) was found in the stem, with a small portion in the lateral buds. Of the GA(4) applied to the needles, 51% of the radioactivity recovered after 24 h was found in the stem and 2% in the lateral buds. Mixtures of tritiated and deuterated GA(4) and GA(9) were injected into elongating shoots of one abundant-flowering family and one limited-flowering family, grown either under conditions inductive for flowering (hot and dry, HD) or under noninductive conditions for flowering (cool and wet, CW). Shoots of both CW- and HD-treated propagules converted [(2)H(2)]GA(9) to [(2)H(2)]GA(51), [(2)H(2)]GA(4), [(2)H(2)]GA(34) and [(2)H(2)]GA(1), whereas [(2)H(2)]GA(4) was converted to [(2)H(2)]GA(34), [(2)H(2)]GA(1) and [(2)H(2)]GA(8). In shoots of both CW-treated clones, the main metabolite of [(3)H]GA(9) was in the GA(51) region. The HD-treated propagules converted more [(3)H]GA(9) to putative GA(4) than the CW-treated propagules. The main metabolite of [(3)H]GA(4) was in the GA(34) region. Radioactive metabolites were also found in the GA(1) and GA(8) regions.