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  • Author or Editor: R.R. Tripepi x
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Nursery management, a course covering practices involved in production of woody landscape plants, was developed for delivery to place-bound students at distant sites around the state. Course subject matter was divided into 41 modules and involved aspects of site selection, cost accounting, plant propagation, nursery trade associations, licensing, as well as container and field production practices. Each module began and ended with a 1- to 2-min introduction and summary to the subject matter, and these segments were taped on location at nurseries in the Pacific Northwest. The lecture portion of each module was taped in a multimedia classroom, and presentation software was used to present text, slides, drawings and animation. Videotape footage of some cultural practices was also inserted into lectures as a “field trip.” Students in the course also received a lecture note guide for all modules in the course. In Idaho, the videotapes were distributed to education centers around the state. The first time the course was offered, 11 students at distant sites and three time-constrained students on campus enrolled. Students contacted the instructor by phone or e-mail. Homework assignments were sent via FAX or e-mail attachments, and tests were sent to the education centers where proctors gave three exams and a final exam. All tests and homework assignments were graded by the instructor located on campus. A videotaped course in nursery management can adequately convey principles involved in landscape plant production, but logistics of mailing videotapes and grading assignments and tests should be carefully evaluated when deciding if a course should be offered at a distance.

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Plant preservative mixture (PPM) is a new broad-spectrum biocide that may be useful for plant tissue culture. The objective of this study was to determine if PPM interfered with adventitious shoot regeneration on leaf explants from several plant species. Leaf explants from Dendranthema grandiflora `Iridon', Betula pendula, Rhododendron catawbiense var. album and R.c. `America' were made from the top two apical leaves on the microshoots. In the first experiment, 0, 0.5, 1, 2, or 4 mL·L-1 PPM were added to species-appropriate regeneration media. In the second experiment, only mum leaf explants were placed on regeneration media containing 0, 0.1, 0.2, 0.3, or 0.4 mL·L-1 PPM. The percentage of explants forming shoots and the number of shoots per regenerating explant were recorded after 4, 6, and 10 weeks, for mum, birch, and rhododendron leaves, respectively. The percentages of shoot regeneration from birch and rhododendron leaf explants were unaffected by up to 4 mL·L-1 PPM, and the number of shoots formed per R.c. album explant were also unaffected by the tested concentrations of PPM. In contrast, the numbers of shoots formed on birch and `America' explants were reduced 48% and 25%, respectively, when 4 mL·L-1 PPM was used in the media. The percentages of shoot regeneration and number of shoots per explant were drastically reduced on mum explants when only 0.5 mL·L-1 PPM was used in the medium. In fact, 0.3 mL·L-1 PPM or higher reduced shoot formation by more than 5-fold. This study demonstrates that the effects of PPM on shoot regeneration from leaf explants are species specific.

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Seeds of `Berken' mung bean [Vigna radiata (L.) R. Wilcz.] were surface-sterilized with NaOCl and then either aerated 24 hours before sowing (routine procedure), planted immediately after the NaOCl treatment, or treated with hot cupric acetate and antibiotics before planting. Nine- or 10-day-old seedlings were used in rooting bioassays. Up to 10% of the seedlings and 17% of the cuttings had collapsed upper stems or wilted leaves. None of the seed treatments completely eliminated the pathogen, but the combination of hot cupric acetate plus antibiotics reduced the quantity of diseased cuttings to 3.3%. A white and two yellow-pigmented (Y1 and Y2) bacteria were isolated from diseased cuttings and used in subsequent pathogenicity tests. The Y2 strain was nonpathogenic. Stems of plants inoculated with the white strain turned brown and collapsed 2 days after inoculation, whereas leaves of plants inoculated with the Y1 strain wilted after 7 days. Electron microscopy, fatty acid analysis, and standard biochemical and physiological tests were used to identify the white strain as Pseudomonas syringae pv. syringae van Hall and the Y1 strain as Curtobacterium flaccumfaciens ssp. flaccumfaciens (Hedges) Collins and Jones. These results emphasize that seeds of mung bean should be checked for seedborne pathogens to avoid experimental artifacts.

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Abstract

Interest in pruning landscape plants is increasing as people realize that attractive trees and shrubs increase aesthetic and property values of homes. In order to illustrate how to prune plants to enhance their appearance and health, a videotape was developed that demonstrates pruning techniques for various woody landscape plants. The tape, “Pruning Your Own Shrubs and Small Trees”, is intended to be used as a learning tool by homeowners, horticulture students, cooperative extension agents, and landscape maintenance personnel.

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Plant Preservative Mixture™ (PPM), a relatively new, broad-spectrum preservative and biocide for use in plant tissue culture, was evaluated as an alternative to the use of conventional antibiotics and fungicides in plant tissue culture. Concentrations of 0.5 to 4.0 mL·L-1 were tested with leaf explants of chrysanthemum (Dendranthem×grandiflora Kitam), European birch (Betula pendula Roth), and rhododendron (Rhododendron catawbiense Michx.). PPM had little effect on the percentage of explants forming shoots and the number of shoots formed per explant in birch and rhododendron, but dramatically reduced both responses in chrysanthemum. Therefore, the effects of PPM must be evaluated for each species of interest prior to use.

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De-inked paper sludge from a newsprint mill was evaluated as a substitute for sofwood bark in container media. Rooted cuttings of `Youngstown' juniper (Juniperus horizonatlis), Fraser photinia (Photinia × fraseri), and `PJM' rhododendron (Rhododendron) were planted in 3-L plastic pots that contained potting media amended with 0%, 20%, 40%, 60%, 80%, or 90% paper sludge and 80%, 60%, 40%, 20%, or 0%, respectively, bark (by volume). All mixes contained 10% sand and 10% peatmoss except for the 90% mix, which lacked peatmoss. After 19 weeks, plant heights were measured for photinia and rhododendron, but average plant width was measured for juniper. Shoot dry weights were also determined for all species. Juniper and photinia seemed to be the most tolerant of media amended with up to 40% paper sludge, whereas rhododendron was the most intolerant species. Shoot dry weights of juniper or photinia were similar for plants grown in media containing 40% or less paper sludge. Shoot dry weights of rhododendron plants grown in 40% sludge were 23% lower than those grown in 0% or 20% paper sludge, which were similar to each other. Plant heights followed similar trends to those of the shoot dry weights. With the exception of juniper, shoot dry weights and heights were drastically reduced if the potting mixes contained more than 40% paper sludge. These results demonstrated that de-inked paper sludge could be substituted for up to 40% of the bark in a container medium for two of the three species tested.

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De-inked paper sludge from a newsprint mill was evaluated as a substitute for softwood bark in container media. Whips, 1.2 m tall, of `October Glory' red maple (Acer rubrum L.), European birch (Betula pendula Roth), and `Royalty' crabapple (Malus L.) were planted in 15-L plastic pots that contained potting media amended with 0%, 20%, 40%, 60%, 80%, or 90% paper sludge and 80%, 60%, 40%, 20%, 0%, or 0%, respectively, bark (by volume). All media contained 10% sand. After 22 weeks, plant heights, trunk diameters, and shoot dry weights were determined. Initial pH of media increased as the amount of paper sludge in the media increased, with the 90% sludge mix having pH 7.2. Paper sludge had a low initial CEC. Physical properties of all sludge-amended media were suitable for tree growth, but media containing 80% or more paper sludge shrank in volume by 10% to 12% by the end of the study. All maple and crabapple trees grown in all sludge-amended media grew as well as those in 80% bark (control mix). In fact, maple and crabapples trees in 40% sludge produced at least 10% and 36% more total shoot biomass, respectively, than trees in 80% bark. Although birch trees grown in 40% or 60% paper sludge grew as well as control plants, those grown in 80% or more sludge were at least 11% shorter and produced 24% less total shoot biomass (leaves, stems, and trunk dry weight) than control trees. These results demonstrated that de-inked paper sludge was a worthy substitute for up to 40% of the bark in a container medium for the three species tested.

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Previous reports of somatic embryogenesis on rose tissues involved an embryogenic callus stage with either a complicated multi-step process or low numbers of embryos being produced. We have produced somatic embryos without a callus stage from leaf explants of the cut rose cultivar `Golden Emblem' by using a two step process. Explants were obtained from microshoots of `Golden Emblem' that had been in culture for three years. All experiments were repeated twice. When explants were maintained on Murashige and Skoog (MS) with 0.4 μM NAA and 0.4 μM kinetin for 10 weeks, 10% or less of the explants produced somatic embryos. Keeping the explants on the NAA/kinetin medium for two weeks, then switching to medium with 0, 0.5, 1.0, or 10.0 μM kinetin for the remaining 8 weeks failed to increase embryo production. Decreasing the time the explants were on the NAA/kinetin medium to 8 or 12 days, and then placing explants on MS medium with 1.0 μM kinetin increased somatic embryo production to a maximum of 25%. By limiting the length of time the rose leaf explants were exposed to auxin, direct somatic embryo production was increased.

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Mung bean (Vigna radiata (L.) R. Wilcz.) cuttings are used in rooting bioassays, and nonexperimental variability must be rigorously controlled to obtain meaningful results. This study was conducted to document bacterial disease problems of mung bean and identify the causal organisms. `Berken' seeds were surfaced sterilized and aerated 24 hr before sowing. Nine-day-old seedlings were used in rooting bioassays. Up to 10% of the seedlings and 17% of the cuttings had collapsed stems or wilted leaves. A white and two yellow (Y1 and Y2) bacteria were isolated from diseased cuttings and used in subsequent pathogenicity tests. The Y2 isolate was nonpathogenic. Stems of healthy mung beans inoculated with the white isolate turned brown and collapsed 2 days after inoculation, whereas leaves of plants inoculated with the yellow isolate wilted after 7 days. Standard biochemical and physiological tests revealed that the white isolate was Pseudomonas syringue pv. syringae van Hall and the yellow isolate was Curtobacterium flaccumfaciens subsp. flaccumfaciens (Hedges) Collins and Jones. This research is the first report of a disease in mung bean caused by P.s. pv. syringae. These results demonstrate the need or disease-free seeds being used in bioassays since both pathogens were seed-borne.

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A plant regeneration system that is compatible with recombinant DNA techniques is required before birch can be genetically transformed. The goal of this research is to develop a shoot regeneration system from leaf discs of European birch (Betula pendula Roth), since this tissue culture procedure is compatible with current transformation technology. Leaves from microplants were excised from stems, cut into approximately 25 mm2 pieces, and placed on WPM media containing differing ratios of NAA (0, 3, 6, 9 μM) to BA (0, 7.5, 15, 22.5 μM) in a 4 × 4 factorial design. Four replicates, each containing 4 leaf pieces, were used per treatment. After 4 and 8 weeks, data was taken including the percent leaves forming shoots and the number of shoots per leaf disc. Only a concentration of 15 or 22.5 μM BA without NAA stimulated shoot formation on leaf discs. Data on the effects of light, media formulations and tissue orientation will be presented. With a reliable and efficient shoot regeneration system for European birch, genetic engineering of this species is now possible.

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