Elongation, rooting and acclimatization of micropropagated shoots from mature material of hybrid larch

Factors were defined for elongation, rooting and acclimatization of micropropagated shoots of Larix x eurolepis Henry initiated from short shoot buds of plagiotropic stecklings serially propagated for 9 years from an 8-year-old tree. Initiation and multiplication were on Schenk and Hildebrandt (SH) medium supplemented with 5 μM 6-benzyladenine (BA) and 1 μM indole-butyric acid (IBA). Stem elongation was obtained in 36% of the shoots on SH medium containing 0.5 μM BA and 63% of the remaining non-elongated shoots initiated stem elongation after transfer on SH medium devoid of growth regulators. Rooting involved 2 steps: root induction on Campbell and Durzan mineral salts and Murashige and Skoog organic elements, both half-strength (CD-MS/2), supplemented with 1 μM of both naphthaleneacetic acid (NAA) and IBA, and root elongation following transfer to CD-MS/2 medium devoid of growth regulators. Repeating this 2-step sequence yielded up to 67% rooted shoots. Acclimatization of plantlets ranged from 83% to 100%. Over 300 plants were transferred to the greenhouse; some showed plagiotropic growth

Increased Resistance of Bt Aspens to Phratora vitellinae (Coleoptera) Leads to Increased Plant Growth under Experimental Conditions

One main aim with genetic modification (GM) of trees is to produce plants that are resistant to various types of pests. The effectiveness of GM-introduced toxins against specific pest species on trees has been shown in the laboratory. However, few attempts have been made to determine if the production of these toxins and reduced herbivory will translate into increased tree productivity. We established an experiment with two lines of potted aspens (Populus tremula×Populus tremuloides) which express Bt (Bacillus thuringiensis) toxins and the isogenic wildtype (Wt) in the lab. The goal was to explore how experimentally controlled levels of a targeted leaf beetle Phratora vitellinae (Coleoptera; Chrysomelidae) influenced leaf damage severity, leaf beetle performance and the growth of aspen. Four patterns emerged. Firstly, we found clear evidence that Bt toxins reduce leaf damage. The damage on the Bt lines was significantly lower than for the Wt line in high and low herbivory treatment, respectively. Secondly, Bt toxins had a significant negative effect on leaf beetle survival. Thirdly, the significant decrease in height of the Wt line with increasing herbivory and the relative increase in height of one of the Bt lines compared with the Wt line in the presence of herbivores suggest that this also might translate into increased biomass production of Bt trees. This realized benefit was context-dependent and is likely to be manifested only if herbivore pressure is sufficiently high. However, these herbivore induced patterns did not translate into significant affect on biomass, instead one Bt line overall produced less biomass than the Wt. Fourthly, compiled results suggest that the growth reduction in one Bt line as indicated here is likely due to events in the transformation process and that a hypothesized cost of producing Bt toxins is of subordinate significance

Effects of buffer system pH and tissue storage on starch gel electrophoresis of allozymes in three tropical tree species

The effects of 16 different electrophoresis buffer pHs, 4 tissue storage conditions and 5 storage times on starch gel electrophoresis of 18 enzymes were determined to design a genetic variation sampling strategy for an isozyme study of 3 tropical tree species, Racosperma auriculiforme, R mangium, and Terminalia superba. The pH of the buffer systems had a significant effect on the number of putative gene loci and alleles resolved, and the staining intensity of the 18 enzymes assayed. For Racosperma species, 2 buffer systems B7 (Tris-citrate gel, pH 9.0: lithium hydroxide-borate electrode, pH 8.5) and H 7 (histidine-EDTA gel, pH 7.6: Tris-citrate electrode, pH 7.7) gave the highest average performance in resolving power. All buffer systems yielded poor results for Terminalia. Freezing of Racosperma embryos for up to 2 months did not seriously affect enzyme activity. However, freezing cotyledon tissue of Terminalia decreased enzyme activity over a 2-month period. In general, frozen tissues either with or without extraction buffer, were consistently better than frozen tissues with extraction buffer and DMSO. Three classes of enzymes were defined, based on their stability under the standardized storage conditions in vivo. Using the best buffer systems (B7 and H7) and tissue storage conditions (To or T1), 42, 43, and 32 zones of activity were resolved for R auriculiforme, R mangium, and T superba, respectively. Genetic inference of enzyme variants was made for 31 and 32 putative gene loci in R auriculiforme and R mangium, respectively. Mean number of putative alleles per locus was 3.0 for R auriculiforme and 2.4 for R mangium.Effets du pH du système de tampons et de la conservation des tissus en électrophorèse sur gel d'amidon d'allozymes chez 3 espèces d'arbres tropicaux. En vue de planifier une stratégie d'échantillonnage de la variabilité génétique de 3 espèces d'arbres tropicaux, Racosperma auriculiforme, R mangium et Terminalia superba, les effets de 16 différents pH de tampons d'électrophorèse (tableau /), de 4 conditions de conservation des tissus et de 5 durées de conservation ont été évalués pour l'électrophorèse sur gel d'amidon de 18 enzymes. La résolution du nombre de loci et d'allèles présumés possibles ainsi que l'intensité de coloration des 18 enzymes étaient influencées de manière sensible par le pH des systèmes de tampons. Pour les espèces de Racosperma, deux systèmes de tampons, B 7 (Tris-citrate, pH du gel 9.0: hydroxyde de lithium, borate- pH de l'électrode 8,5) et H7 (histidine, EDTA, pH du gel 7,6: Tris-citrate pH de l'électrode 7,7) ont donné le meilleur pouvoir moyen de résolution (fig 1-11, tableau II). Tous les systèmes de tampons ont entraîné des résultats insatisfaisants chez Terminalia. La congélation des embryons de Racosperma pour plus de 2 mois n'a pas affecté sérieusement l'activité enzymatique. En revanche, la congélation des cotylédons de Terminalia au-delà de 2 mois a diminué l'activité enzymatique. En général, les tissus congélés avec ou sans tampon d'extraction, donnaient constamment de meilleurs résultats que les tissus congélés avec le tampon d'extraction supplémenté de DMSO (fig 12). Trois classes d'enzymes ont été définies, sur la base de leur stabilité sous les conditions in vivo standardisées (tableau III). En utilisant les meilleurs systèmes de tampons (B7 et H7) et conditions de conservation (T0 ou T1), 42, 43 et 32 zones d'activité étaient séparées respectivement pour R auriculiforme, R mangium et T superba. L'inférence génétique de 31 et 32 loci présumés a été conduite pour R auriculiforme et R mangium, respectivement (fig 13-17). Le nombre moyen d'allèles présumés par locus était de 3,0 pour R auriculiforme et de 2,4 pour R mangium (tableau IV)