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R.J. Henny and D.J. Norman

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J. Naraguma, J.R. Clark, and R.J. Norman

A spring application of 19 g CO(15NH2)2/plant at 2.49% atom percent enrichment was made in Mar. 1995 on 2-year old, field-grown `Arapaho' blackberry plants. Individual plants were harvested during the study at preharvest (late May), postharvest (mid-July), and early dormancy (late October). The following plant parts were separated for analysis: roots, primocanes, floricanes, primocane leaves, floricane leaves, fruits. Soil samples were also taken from within the drip line of the plants at each sample date. Plant tissues were washed, dry weights measured and ground for acid digestion, total N determination and 15N analysis. Samples were measured for 15N atom percent abundance by a isotope ratio spectrometer. The whole-plant dry matter in creased during the season from 53 g in May to 153 g in October. Plants sampled in October had a greater amount of dry matter in roots than in any other tissue. There was a decreased total N content in all vegetative tissues (leaves and canes) from May to October. The maximum fertilizer 15N percent recovery was 43% (October) and the minimum was 12% (May) from the total plant tissues. Compared to other plant tissues, floricane leaves and primocanes recovered significantly more fertilizer 15N in May, while roots and primocane leaves recovered more in October. Floricanes and fruits did not increase in 15N levels during the sampling period. Fertilizer 15N recovered in the soil amounted to 35.5% of the applied with 4.5% found in the inorganic fraction, 31% in the organic fraction. There were no statistical differences in percent recovery of the fertilizer 15N among sample dates in the topsoil. October 15N percent recovery was much lower than May in the subsoil, indicating a downward movement of N by leaching. Averaging all sample dates, 59.5% of the labeled fertilizer was accounted for in the plant and soil, with the remaining portion probably lost via volatilization, leaching, and/or denitrification.

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D.J. Norman, R.J. Henny, and J.M.F. Yuen

Twenty commonly grown Dieffenbachia cultivars were tested for their resistance to diseases affecting production caused by the following bacterial and fungal pathogens: Xanthomonas campestris pv. dieffenbachiae (McCulloch and Pirone) Dye, Erwinia chrysanthemi Burk, Fusarium solani Sacc, and Myrothecium roridum Tode ex Fr. Two isolates of each pathogen were used to compare heterogenic pathogen populations to the relatively homogenetic asexually produced cultivars. Cultivars having horizontal resistance toward tested pathogens could then easily be identified. The cultivars Camille, Compacta, and Parachute showed the broadest horizontal resistance, with resistance toward three of the four pathogen groups tested. Disease resistance identified in this research permits the selection of plants to be used in breeding, and also creates a baseline to compare resistance of newly developed cultivars.

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R. J. Henny, J. Chen, and D.J. Norman

Species and cultivars of Dieffenbachia Schott. (Araceae Juss.) have been important ornamental foliage plants for many decades. Their attractive foliar variegation, adaptability to interior environments, and ease of production are major reasons for their importance as ornamental foliage plants. Approximately 20 cultivars are commercially produced in Florida. Previously, most new cultivars were clones introduced from the wild or chance mutations of existing cultivars. Currently, cultivars are introduced into production from plant breeding programs (Henny 1995a, b; Henny and Chen, 2003; Henny et al., 1987). The hybrid Dieffenbachia `Sterling' was developed by the tropical foliage plant breeding program at the Mid-Florida Research and Education Center.

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R.J. Henny, J. Chen, and D.J. Norman

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D.J. Norman, J.M.F. Yuen, and R.J. Henny

Twenty-two spathiphyllum cultivars were evaluated for resistance to Cylindrocladium root rot (CRR). Four isolates of the fungus Cylindrocladium spathiphylli Shoult., El-Gholl & Alf. were selected from two different locations each in Florida and Hawaii. Spores of isolates were applied as a soil drench in replicated experiments using a randomized complete block design. The most severe symptoms were those produced by C. spathiphylli isolates from Hawaii. None of the spathiphyllum cultivars tested were highly resistant to CRR although resistance among the cultivars was observed. The cultivars Chris and Textura were the most promising cultivars, having fairly uniform resistance to the four isolates of C. spathiphylli. The cultivars Cupido, Daniel, Frederik, Jetty, and Vanessa were moderately resistant when combined data from all tests were analyzed. Results from this research permit the selection of more resistant breeding lines and also creates a baseline against which resistance of newly developed cultivars can be compared.

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D.J. Norman, J.M.F. Yuen, and R.J. Henny

One cut-flower and 14 pot anthurium cultivars were screened for resistance to anthurium blight by spraying four isolates of Xanthomonas campestris pv. dieffenbachiae (McCulloch and Pirone) Dye onto leaf surfaces in replicated experiments. Varying degrees of resistance were observed among the 15 cultivars tested. The pot cultivars Julia and Gemini were the most resistant, while the cut-flower cultivar Hearts Desire was the most susceptible. Each cultivar displayed different degrees of resistance to individual isolates of the pathogen. The results of this research permit the selection of clones with greater resistance for use in breeding and also create a baseline for comparing resistance of newly developed cultivars.

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R.J. Henny, D.J. Norman, and J. Chen

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R.J. Henny, J. Chen, and D.J. Norman

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R.J. Henny, T.A. Mellich, and D.J. Norman

Thirty-one spathiphyllum (Spathiphyllum Schott.) cultivars were evaluated for flowering response following treatment with gibberellic acid (GA3). Greenhouse-grown plants were treated once with 250 mg·L-1 (ppm) GA3 applied as a foliar spray. Within 16 weeks after treatment all GA3-treated plants had flowered but none of the untreated controls produced flowers. `Vickilynn' (14.1 flowers/plant after 16 weeks), `Piccolino' (12.8), `Mascha' (12.6), `Chris' (11.7), `Alpha' (11.7), and `Daniel' (11.0) produced significantly more flowers than other cultivars. The cultivars producing the fewest flowers per plant after 16 weeks were `Sierra' (2.5), `S1008' (3.2), `Rica' (3.4), `Sonya' (4.3), `Vanessa' (5.1), `S18' (5.5) and `S4002' (5.6). `Alpha,' `Textura,' `Daniel,' `Mascha,' `S1007', and `Showpiece' had significantly better flower quality. `S1008,' `Codys Color', and `Petite' had poor flower quality. `Mascha' was the earliest cultivar to bloom producing maximum flower counts during weeks 9 to 10 after treatment while `Vanessa' was the latest to flower with peak bloom occurring 15 to 16 weeks after treatment. Most cultivars reached peak bloom at 11 to 13 weeks after treatment. Results indicate sufficient genetic variability in spathiphyllum flowering response to GA3 treatment exists to permit cultivar selections based on differences in flowering time, number of flowers and flower quality.