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M.W. George and R.R. Tripepi

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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Mary W. George and Robert R. Tripepi

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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James R. Ault

Shoot proliferation cultures were established in vitro using flower-stem explants from two different interspecific hybrid plants of Liatris. Explants taken on two dates from field-grown plants were successfully established and axillary shoot growth promoted on a medium consisting of Murashige and Skoog basal salts and vitamins with 30 g·L-1 sucrose, 1.0 μm BA, and 7.0 g·L-1 agar, with a medium pH = 5.7. Initial explant contamination rates were significantly higher among explants collected later in the growing season. Addition of BA (1.0, 2.0, 4.0, 8.0, or 16.0 μm) improved shoot formation compared to the control for both plants. Proliferation rates differed between the dates of establishment, the plants, and the BA treatments. Shoots rooted readily in medium without PGRs or with 1.0, 2.0, 4.0, or 8.0 μm K-IBA. Overall rooting was 88%. About 90% of the plants rooted in the presence of 1.0 μm K-IBA were successfully established in the greenhouse. Chemical names used: 6-benzyl adenine (BA); potassium salt of indole-3-butyric acid (K-IBA).

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Thiago Vieira da Costa, João Alexio Scarpare Filho, and Matthew W. Fidelibus

Seedless’, but the highest concentration tested, 750 ppm, had no obvious effect on fruit or foliage ( Fidelibus et al., 2007 ). However, higher rates of ethephon have been shown to be an effective postharvest defoliant of grapevines in tropical areas

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Amir Rezazadeh, Richard L. Harkess, and Guihong Bi

synthetic cytokinin, is commonly used to promote branching in ornamental plants ( Latimer and Freeborn, 2008 ). A previous study showed a foliar spray of BA at 300 or 600 ppm doubled the number of branches in ‘White Swan’ and ‘Double Decker’ purple

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Alexander D. Pavlista, Dipak K. Santra, James A. Schild, and Gary W. Hergert

,000 to 0.031 ppm GA 3 . A sticker-spreader-type surfactant, X77, at 0.125% was added to solutions applied to foliage until determined not to be needed in a greenhouse test in 2007 (unpublished data). Seed application experiments. Emergence tests were

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Smit le Roux and Graham H. Barry

× domestica ) and pear ( Pyrus communis ) fruit trees to reduce and control vegetative growth ( Miller, 2002 ). Costa et al. (2001) reported that applications of 100 ppm ProCa significantly reduced shoot growth and increased fruit size in pears. ProCa acts

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Piyada Alisha Tantasawat, Atitaya Sorntip, and Paniti Pornbungkerd

, Papadopoulos et al. (2006) reported that a 2.5-ppm KIN foliar spray had beneficial effects on plant growth (taller plants, greater leaf area, and fresh weight of leaves and stems), resulting in higher marketable yield in the spring–summer crop and in larger

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Randall P. Niedz

preparation and maintenance of the protoplast and tissue cultures and Assaf Guri of Plant Cell Technology for generously providing PPM samples for testing.

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Eugene K. Blythe

prepared 4.75 to 5.50 inches in length with four vegetative buds, trimming 0.5 inch above and below a vegetative bud. Caliper of the cuttings ranged from 0.35 to 0.40 inch. Auxin solutions were prepared by diluting Dip ’N Grow (10,000 ppm IBA + 5000 ppm NAA