by Claire Morin | 30 January 2019
Published in Theoretical and Applied Genetics 86: 81-87
The usefulness of random amplified polymorphic DNA (RAPD) in assessing the genetic stability of somatic embryogenesis-derived populations of black spruce [Picea mariana (Mill.) B.S.P.] was evaluated. Three arbitrary 11-mer primers were successfully used to amplify DNA from both in-vivo and in-vitro material. Twenty-five embryogenic cell lines, additional zygotic embryos and megagametophytes from three controlled crosses involving four selected genotypes of black spruce were used for the segregation analysis of RAPD variants. Ten markers were genetically characterized and used to evaluate the genetic stability of somatic embryos derived from three embryogenic cell lines (one cell line per cross, 30 somatic embryos per cell line). No variation was detected within clones. The utilization of RAPD markers both for the assessment of genetic stability of clonal materials and to certify genetic stability throughout the process of somatic embryogenesis is discussed.
by Claire Morin | 30 January 2019
Published in Plant Cell, Tissue and Organ Culture 27: 95-103
Different carbohydrates were investigated for somatic embryo development of black spruce and red spruce. They were tested in a basal maturation medium consisting of Litvay’s salts at half-strength containing 1 g l-1 glutamine, 1 g l-1 casein hydrolysate, 7.5 mM abscisic acid, and 0.9% Difco Bacto-agar. A comparison of different sucrose concentrations showed that 6% was optimal for embryo development. Among the nine carbohydrates tested, sucrose, fructose, glucose, maltose, and cellobiose supported embryo development while arabinose, mannitol, myo-inositol, and sorbitol did not. A comparison of sucrose, glucose, and fructose at three concentrations showed that the general pattern of response for both species followed concentration expressed as a percentage, independent of the molarity of carbohydrate in the medium. Interspecific differences were observed concerning carbohydrate requirements. For red spruce, 6% fructose was found best for embryo development, while no such preference was observed for black spruce. No significant difference was observed in the number of embryos produced with 6% sucrose or 3% sucrose plus an equimolar concentration of either mannitol, sorbitol, or myo-inositol in the maturation medium, suggesting that the effect of the carbohydrate on the maturation was partly osmotic.
by Claire Morin | 30 January 2019
Published in American Journal of Botany 86(10): 1373-1381
Plants of black spruce (Picea mariana, N = 7047 individuals) and white spruce (P. glauca, N = 3995 individuals) were regenerated from a total of 87 clones over a 5-yr period by somatic embryogenesis to study factors that might be associated with the appearance of variant phenotypes. Morphological evaluation of the plants showed several types of variation. These variations were grouped into nine types: dwarfism (type A), reduced height with various form anomalies (types B, C, and D), needle fasciation (type E), abnormality in tree architecture (type F), variegata phenotype (type G), and plants with an overall regular morphology but smaller than normal plants (type H). Plagiotropic plants were also observed (type I). Each plant from types A to H (except type C where no plants survived more than 6 mo) had retained its phenotype over 4-5 yr of growth. Some of the variant types could be related to chromosomic instability: chromosome counts showed aneuploid cells for type-A and type-D plants. The type I (plagiotropism) was not related to genetic instability but rather to physiological disorders. In total, spruce variants of types A-H were obtained at relatively low frequencies, i.e., 1.0% (39/3995) for white spruce and 1.6% (110/7047) for black spruce. Statistical analyses, conducted with family, clone, and time in maintenance as variables, showed that clone was the most important source of genetic instability followed by time in maintenance.
by Claire Morin | 30 January 2019
Published in Plant Science 77: 233-242
Embryogenic tissue was obtained from immature zygotic embryos of black spruce (Picea mariana) and mature zygotic embryos of red spruce (Picea rubens). Embryogenic tissues were induced and maintained on half-strength Litvay’s medium supplemented with 10 mM 2.4-dichlorophenoxyacetic acid (2.4-D), 5 mM benzylaminopurine (BAP), 1 g/l casein hydrolysate, 500 mg/l glutamine, 1.0% (w/v) sucrose, and 0.9% (w/v) Difco Bacto-agar. To improve the maturation of somatic embryos, different gelling agents and ammonium nitrate concentrations were tested with a basal maturation medium consisting of HLM basal medium supplemented with 1 g/l glutamine, 1 g/l casein hydrolysate, 6% (w/v) sucrose, and 7.5 mM abcisic acid (ABA). The number of somatic embryos was significantly higher on medium solidified with Gelrite gellan gum than with Difco Bacto-agar. Corn, potato, wheat, or rice starches as gelling agents either did not influence or drastically reduced the development of black spruce somatic embryos. An ammonium nitrate concentration 3.4–10 mM for black spruce or 3.4–15 mM for red spruce was found to be optimal for embryo development. Maintenance of the embryogenic tissue under light or in darkness and use of different fluorescent lamps during the maturation stage did not influence the total number of black spruce somatic embryos produced. However, a maximum number of germinating embryos was produced when the embryogenic tissue was maintained in darkness, followed by a maturation stage in light.
by Marie-Claude Boileau | 30 January 2019
Published in Hydrological Processes 22: 4163-4172
In boreal forested wetlands, the observed increase in the water table level after clearcutting (watering-up) is often a threat to sustained ecosystem productivity. Hydrologic recovery refers to the processes by which a water table progressively drops back to its initial level after the cut. In eastern Canada, drainage is used operationally after clearcutting wet sites in order to lower the water table level and accelerate hydrologic recovery. The objective of this study was to evaluate the duration of the watering-up caused by timber harvesting and the extent to which drainage affected the water table recovery on five peatlands and three hydromorphic mineral sites located in the St. Lawrence Lowlands of Québec (Canada). The mixed wood stands studied are dominated by balsam fir (Abies balsamea (L.) Mill.), eastern white cedar (Thuja occidentalis L.), and red maple (Acer rubrum L.). Results indicate that, 10 years after clearcutting, water table levels in undrained plots are still 5 to 7 cm higher than the pre-cut levels. The slight recovery in water table level plateaued after the third year. Rainfall interception by vegetation was also monitored, and after 10 years had reached nearly 50% of the pre-cut rate. The immediate water table drawdown following drainage mitigated watering-up within 40 m of a ditch. The persistent watering-up observed in this study should encourage using sylvicultural systems adapted to boreal forested wetlands in order to prevent productivity loss and stand conversion.
