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R. Kasten Dumroese, Robert L. James and David L. Wenny

Inoculum of Douglas fir root diseases caused by the fungi Fusarium and Cylindrocarpon is carried from crop to crop in reused containers. Soaking containers for 90 seconds in 80 °C water removed ≈99% of Fusarium and 100% of Cylindrocarpon inoculum between growing cycles. Overall seedling growth was also improved: seedlings grown in containers soaked between growing cycles were 10% taller and had 20% more biomass than seedlings grown in nonsoaked containers. We obtained a 13% increase in the number of deliverable seedlings from containers soaked in hot water between crops, from the use of copper coated containers, or from both practices combined.

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John L. Edson, David L. Wenny and Annette Leege-Brusven

In vitro—derived microshoots of antelope bitterbrush, incubated for 1 month in media supplemented with 0.44 μm BA, grew 0.8 and 1.1 cm longer in woody plant medium (WPM) compared to full-strength and half-strength Murashige and Skoog (MS) media, respectively. Explants cultured in WPM supplemented with 0.44 μm BA and 0.54 μm NAA produced a mean of five axillary shoots per explant. Explants dipped in 0.1% IBA or 0.1% NAA rooted best in 0.1% IBA with 89% success ex vitro vs. 60% success in vitro. Survival of acclimatized plantlets rooted ex vitro was 95%, while 50% survived when rooted in vitro. After 1 year of greenhouse growth, 98% of plantlets survived and flowered. Chemical names used: benzyladenine (BA), 3-indolebutyric acid (IBA), 1-naphthaleneacetic acid (NAA).

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John L. Edson, David L. Wenny and Annette Leege-Brusven

Idaho's population of Pacific dogwood (Cornus nuttallii Audubon) has declined. Propagation of disease-resistant clones would be useful to horticulturists and conservation biologists. In vitro-derived microshoots, incubated for 1 month on woody plant medium supplemented with 6.04 mm calcium gluconate and 4.44 μm benzyladenine, produced an average of 3.1 axillary microshoots per explant. Up to 62% of the elongated microshoots had rooted ex vitro 5 weeks following a 4.5%IBA talc dip. Plantlets resumed shoot growth within 2 months of acclimatization, and 70% survived after 1 year. This protocol is more rapid and efficient than propagation by layering or rooting the difficult-to-root stem cuttings of this species. Chemical names used: 2,3,4,5,6-pentahydroxy-caproic acid (calcium gluconate), benzyladenine (BA), 3-indolebutyric acid (IBA).

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Robert R. Tripepi, Mary W. George, R. Kasten Dumroese and David L. Wenny

European birch (Betula pendula Roth) seedlings (1+ 0 plugs) were planted in a container growth medium amended with 0, 1.2, 2.4, or 3.6 kg/m3 of a commercial hydrogel and watered either daily or once every 3 or 5 days. When hydrogel was incorporated in the growth medium, shoot and root dry weights and lea area were reduced by 19, 29 and 18%, respectively, compared to controls. Shoot height, stem diameter and shoot:root ratio were unaffected by hydrogel amendment rate. Compared to seedlings in polymer-amended media, plants growing in medium without hydrogel had significantly lower stomata1 conductance and transpiration on fewer than 25% of the measurement dates. Irrigation frequency significantly affected all plant growth Indices and stomata1 parameters; seedlings irrigated daily grew the most and had the highest stomata1 conductance and transpiration. Although polymer-amended media held more water than the medium without hydrogel at all measured tensions, this moisture was retained in the expanded gel rather than being available for plant uptake at higher tensions. The hydrogel appeared to have little benefit for container production of birch.