Atlantic white cedar (AWC;
Chamaecyparis thyoides
), an aromatic evergreen conifer native to swamps and bogs along the Atlantic and Gulf coasts of the eastern United States was once an important ...species for timber production due to its durable wood. However, native populations have declined over the past two centuries. We established an in vitro propagation system for AWC via somatic embryogenesis (SE) without the use of plant growth regulators (PGRs). Whole megagametophytes with zygotic embryos from immature AWC cones were cultured on a modified half-strength embryo maturation (EM) medium with three different PGR treatments, including one devoid of PGRs. Both PGR treatment and cone collection date had significant effects on embryogenesis induction, with EM with no PGRs giving the highest embryogenesis induction, which ranged as high as 27%. We also conducted experiments to determine the effects of activated carbon (AC) and abscisic acid (ABA) in the maturation medium on production of mature somatic embryos. AC significantly affected this variable, with 2 g l
−1
producing more embryos than 0 g l
−1
. Application of exogenous ABA not only failed to improve production of mature somatic embryos, the highest level tested (200 µM), apparently lowered production of mature embryos compared to the 0 ABA control. The highest numbers of mature somatic embryos per ml of plated embryogenic suspension (32–37) were produced on medium with 2 g l
−1
AC and levels of ABA at 100 µM or lower. The SE system described here has the potential to contribute the restoration of Atlantic white cedar to its native habitat.
Emerald ash borer (
Agrilus planipennis
; EAB) has devastated populations of ash (
Fraxinus
spp.) trees in dozens of U.S. states and Canada over the past few decades. The continued survival of ...scattered ash trees known as “lingering ash” in heavily infested natural stands, however, offers evidence of genetic resistance or tolerance to EAB. These surviving or “lingering” ash individuals may form the basis for reforestation programs in EAB-impacted areas, and clonal mass-propagation of these genotypes can help accelerate these efforts. Between 2013 and 2018, we initiated embryogenic cultures by culturing immature zygotic embryos from open-pollinated (OP) seeds collected from several surviving white ash and green ash trees in Michigan and Pennsylvania. In addition, in 2018, we initiated cultures from crosses made between lingering green ash parents from the USDA Forest Service ash breeding program in Ohio. Somatic embryos were produced by growing cultures in liquid suspension, followed by fractionation and plating on semisolid medium to produce developmentally synchronous populations of somatic embryos. Somatic embryo germination and conversion were enhanced by a combination of pre-germination cold treatment and inclusion of activated charcoal and gibberellic acid in the germination medium. Ash somatic seedlings derived from OP explants grew rapidly following transfer to potting mix and somatic seedlings representing nine ash clones were acclimatized, grown in the greenhouse and planted in a preliminary field test, along with EAB-resistant Manchurian ash (
F. mandshurica
) and EAB-susceptible control seedlings. Somatic seedlings have now been produced from cultures that originated from seeds derived from the progeny of lingering green ash parents and an ex vitro germination protocol has shown some promise for accelerating early somatic seedling growth. Results of this research could provide the basis for scaled-up production of EAB-resistant ash varieties for seed orchard production for forest restoration and cultivar development for urban tree restoration.
KEY MESSAGE : Embryogenic cultures of eastern and Carolina hemlocks could be initiated, and somatic embryos and plantlets produced using standard conifer protocols and media. Embryogenic hemlock ...cultures were cryostored and recovered. Eastern hemlock (Tsuga canadenesis) and Carolina hemlock (Tsuga caroliniana) are threatened with extirpation from their native ranges in eastern North America by the introduction of the hemlock woolly adelgid (HWA; Adelges tsugae), an exotic insect pest that has already killed millions of hemlock trees. Efforts to conserve and restore these members of the Pinaceae could be greatly enhanced by the availability of an in vitro propagation system. We conducted experiments to initiate embryogenic cultures from eastern and Carolina hemlock zygotic embryos at different stages of development using three media supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D) and 6-Benzylaminopurine (BA). Cone collection date, medium and source tree had significant effects on induction of embryogenic tissue from zygotic embryo explants of both species, which ranged as high as 52 % for eastern hemlock and 17 % for Carolina hemlock. Embryogenic hemlock cultures could be cryostored using a protocol employing sorbitol and DMSO, and recovered following several months of frozen storage. Transfer of embryogenic tissue from proliferation media containing 2, 4-D and BA to a Litvay medium with abscisic acid promoted the development of somatic embryos, which were stimulated to mature by slow drying under semi-permeable plastic film. Embryos moved to an imbibition-germination medium without plant growth regulators and incubated in the light elongated and subsequently germinated. A small number of germinated embryos survived transfer to ex vitro conditions and grew into somatic seedlings. The embryogenesis and cryostorage systems developed in the study are already being integrated with hemlock breeding efforts to develop clones with resistance or tolerance to HWA.
Embryogenic cultures of loblolly pine (Pinus taeda L.), slash pine (Pinus elliottii Engelm.), longleaf pine (Pinus palustris Mill.) and slash pine x longleaf pine hybrids were initiated from immature ...seeds on an initiation medium containing 13.57 micromolar 2,4-dichlorophenoxyacetic acid and 2.22 micromolar benzylaminopurine. Embryogenic cultures proliferated and somatic embryos developed, matured and germinated following a modified protocol and media originally developed for radiata pine (Pinus radiata D. Don.) somatic seedling production. A discrete, light-sensitive pre-germination stage and a later germination (radicle emergence) stage were identified by the differential response of somatic embryos to light of different wavelengths. Different light quality treatments were applied during the pre-germination and germination steps, using cool white fluorescent bulbs or light-emitting diodes (LEDs), or both. In general, red wavelengths provided by LEDs during these steps resulted in higher frequencies of somatic embryo germination (up to 64%) and conversion (up to 50%), longer tap roots and more first-order lateral roots than the standard cool white fluorescent treatments or treatment with blue wavelengths from LEDs. In addition, exposure to red light allowed germination of somatic embryos of some clones that failed to produce germinants under fluorescent light. Germination and conversion were further enhanced by sequential application of cool white fluorescent light and red light, resulting in up to 100% germination and conversion in one experiment. Longleaf pine somatic embryos were especially responsive to the light quality treatments, resulting in the first report of somatic seedling production for this species.
Cryopreservation has become anessential tool for operational application offorest tree embryogenic cultures, due to thelong evaluation periods needed for treesregenerated from these cultures. ...Fiveyellow-poplar (Liriodendron tulipifera)and seven sweetgum (Liquidambar spp.)embryogenic culture lines werestored in liquid nitrogen for 48 hours, afterwhich they were thawed and tested for regrowthand ability to produce somatic seedlings.Combinations of two sorbitol pretreatments andthree dimethylsulfoxide (DMSO) cryoprotectantlevels were evaluated for their impact onrecovery following cryogenic storage. The bestresults were obtained with 0.4 M sorbitol and5% DMSO, which provided 100% recovery.Somatic seedlings were regenerated from allculture lines and treatments, except for atransgenic sweetgum line.PUBLICATION ABSTRACT
Effects of photoautotrophic and photomixotrophic growth conditions on adventitious shoot regeneration from leaf explants of eastern cottonwood (Populus deltoides Bartr. ex Marsh.) were investigated. ...Rooting and proliferating shoot cultures (Stage I) were grown in either an elevated (1500 ppm) CO2 concentration (CO2) at high photosynthetic photon flux (PPF; approximately 150 μmol m⁻² s⁻¹) (photoautotrophic condition) with 0, 10 or 30 g l⁻¹ sucrose or under standard conditions (ambient (360 ppm) CO2 at low PPF (approximately 60 μmol m⁻² s⁻¹) with 30 g l⁻¹ sucrose). Leaves harvested from these cultures were analyzed for soluble sugars and were used as explants for adventitious shoot regeneration (Stage II), which was also carried out under photoautotrophic and standard conditions. Photoautotrophic conditions during Stage I promoted growth of rooting shoots but inhibited axillary shoot proliferation. Photoautotrophic conditions during Stage II suppressed callus and adventitious bud production from leaf explants compared with standard conditions. The regeneration environment appeared to be more important in controlling bud formation than the conditions under which the donor shoots were grown. Regardless of Stage I treatment, bud production was up to 100-fold higher for leaves cultured under standard conditions than under photoautotrophic conditions. Once adventitious buds were differentiated from the leaf tissues, however, their elongation was faster under photoautotrophic conditions than that under standard conditions, with some shoots reaching 10 mm in length on leaf explants cultured under photoautotrophic conditions. Because total leaf soluble sugar concentration was always lowest in shoots under standard conditions, which also yielded the highest bud production, the results suggest that endogenous starvation enhanced shoot production.
Interpersonal skills have been shown to be foundational for effective leadership in many settings. The need for those skills among educational administrators was examined in three stages. First, the ...interpersonal skill level of 170 educational administration graduate students was evaluated in four categories (attending, empathy, respect, concreteness). Students' skill levels approximated those of the general population. Second, 14 school administrators received 50 hours of interpersonal skill and group management training. Pre-, post-, and postpost-training assessments showed marked improvement and sustained effects on all four skill categories. However, methodological considerations limits the generalizability of the results. The third phase employed a pre-post treatment (n = 10) and control-group (n = 12) design with blind raters. Significant gains were found for the treatment group on three of the four skills evaluated, after only 12 hours of training. Implications for interpersonal skills training for educational leaders are addressed.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NMLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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