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Valerie M. Jonas and Kimberly A. Williams

A series of experiments were conducted to determine the ranges of irrigation frequency and N and P fertilization regimes that produce ivy geranium (Pelargonium peltatum L.) plants of optimum commercial quality. Two cultivars, `Sybil Holmes' and `Amethyst', were grown. Data collected included fresh and dry weights, ratings, leaf area, height, width, ratings, and nutrient tissue content. Individual pots were weighed daily and irrigated when weight of pots dropped by 15%, 30%, 45%, or 60% of container capacity (CC). Leaf water potential was measured using a pressure chamber. At both mid and end of crop, plants irrigated when pot weight dropped by 30% of CC were under least water stress (e.g., water potential of –7.0 to –4.7 MPa). Irrigation frequencies at 15%, 45%, or 60% of CC had similar water potentials (e.g., –9.9 to –9.1 MPa). At 15%, a plausible explanation of the stress is that oxygen was limiting in the root zone due to water-logging; at 45% and 60%, water was the limiting factor. Single factor experiments with N at five concentrations ranging from 2 to 32 mm and P at five concentrations ranging from 0.08 to 2.56 mm were conducted. Quadratic equations were fit to curves of growth responses plotted against concentration of N or P applied. As an example of results, N fertilizer rates of 16 and 32 mm for `Amethyst' resulted in similar, commercially acceptable dry weights (37g), but different N tissue concentrations of 3.4% and 3.9% respectively. For `Sybil Holmes', N fertilizer rates of 10 and 26 mm resulted in similar dry weights (21g) but different tissue concentrations of 2.8% and 3.4%, respectively.

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Terri Woods Starman and Shane Abbitt

Our objective was to distinguish between eight cultivars of two geranium species, Pelargonium ×hortorum L.H. Bailey (cutting and seed geranium) and Pelargonium peltatum (L.) L'Hér. ex Ait. (ivy geranium), and evaluate their genetic relationships using the nucleic acid scanning techniques of DNA amplification fingerprinting (DAF) and/or arbitrary signatures from amplification profiles (ASAP). Cultivars used in the study represented three commercial types: cutting, seed, and ivy geranium. Two seed geranium cultivars from each of the Dynamo and Orbit series were included. Cutting geranium cultivars were `Designer Lilac Chiffon' and `Starburst Red' and the ivy geraniums were `Bernardo Guiber' and `Vinco Guivin'. The ASAP amplification protocol used one of two arbitrary octamer primers, followed by reamplification with one of four different minihairpin primers. ASAP profiles were complex, with 66% of bands being polymorphic and useful in distinguishing between cultivars. Genetic relationships were evaluated by principal coordinate analysis and cluster analysis based on the Jaccard distance estimator. This analysis grouped cultivars by species according to commercial type, i.e., seed geraniums were in one large group, the cutting geraniums were grouped together, and the ivy geraniums were a separate branch.

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George P. Opit, Yan Chen, Kimberly A. Williams, James R. Nechols, and David C. Margolies

In three experiments, damage caused by twospotted spider mite (TSSM; Tetranychus urticae Koch) was correlated with the quality of ivy geranium [Pelargonium peltatum (L.) L'Her ex Aiton], and the action threshold for TSSM on ivy geranium was developed. Ivy geranium quality was measured as overall plant quality—plant size and form, and leaf greenness and glossiness—leaf browning, and leaf distortion. Young plants with high initial TSSM numbers (30 TSSM/plant) exhibited the greatest damage, suggesting that monitoring for TSSM early in the plant production cycle is necessary to prevent extensive damage. The leaf distortion index and overall plant quality were correlated with cumulative TSSM density and marketability in 4-week-old plants infested with 30 TSSM, whereas leaf browning was not correlated with either. Thus, either leaf distortion or overall plant quality can be used to measure economic damage resulting from TSSM. The action threshold for TSSM on ivy geranium was determined using overall plant quality. When the predatory mite, Phytoseiulus persimilis Athias-Henriot, is used to control TSSM, the action threshold was found to be 2 TSSM/leaf. Results also showed that fertilizer combinations of 8 or 24 mm nitrogen and 0.32, 0.64, or 1.28 mm phosphorus had no effect on cumulative TSSM density. When P. persimilis was released at predator: prey ratios of 1:60, 1:20, and 1:4, TSSM damage, measured as both leaf distortion and overall plant quality, was significantly reduced at 1:4 and 1:20, but not at 1:60. A 1:4 rate resulted in the most marketable plants. These results suggest that P. persimilis should be released at a rate of 1:4 when the TSSM action threshold is reached.

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W. Roland Leatherwood, John M. Dole, Ben A. Bergmann, and James E. Faust

synthesis using five taxa ( Euphorbia pulcherrima ‘Visions of Grandeur’, Impatiens hawkeri ‘Sonic Red’, Pelargonium peltatum ‘Mandarin’, P . × hortorum ‘Kardino’, and Petunia × hybrida ‘Suncatcher Coral Prism’). Expt. 3 tested the hypothesis that

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Michael S. Uchneat, Kathryn Spicer, and Richard Craig

The objective of this study was to identify geranium cultivars that exhibit differential reactions to floral inoculation with Botrytis cinerea Per. ex. Fr. Sixty-two genotypes, including both cultivars and breeding lines, were evaluated from several Pelargonium species. Resistant genotypes included the diploid Pelargonium peltatum (L.) L'Herit. cultivar King of Balcon and the diploid Pelargonium ×hortorum L.H. Bail. cultivar Ben Franklin, as well as the diploid Pelargonium peltatum accession 93-1-33 developed from an accession obtained from South Africa. Susceptible genotypes included the putative tetraploid Pelargonium peltatum cultivar Simone. Floral resistance was not correlated with foliar resistance. Diploid genotypes appeared to have greater resistance than tetraploid genotypes, and P. peltatum cultivars more resistance than P. ×hortorum cultivars. In addition, the association of petal number and resistance was investigated.

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Ritu Dhir, Richard L. Harkess, and Guihong Bi

Ivy geranium ( Pelargonium peltatum L.) is an important floriculture crop but it does not tolerate the high temperatures of southeastern U.S. summers. Under heat stress, the newly developing leaves of ivy geranium are partially or completely white

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Kellie J. Walters and Roberto G. Lopez

influenced by ALK and TEMP. Materials and Methods Plant material. Cuttings of verbena ( Verbena peruviana ) ‘Aztec Blue Velvet’ were stuck in 102-cell liner trays, and ivy geranium ( Pelargonium × peltatum ) ‘Precision Pink’ were stuck in 104-cell liner

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Anusuya Rangarajan and Theodore W. Tibbitts

Oedema, a physiological disorder, affects several cultivars of ivy geranium [Pelargonium peltatum (L.) L `Hér. ex Ait) when grown in greenhouses. This study investigated the regulation of oedema on this crop using far-red radiation because these wavelengths inhibited the injury on Solanaceous sp. Plants were exposed to far-red radiation from Sylvania #232 far-red lamps on abaxial and adaxial surfaces of leaves. A far-red photon flux of 15 to 20 μmol·m-2·s-1 (700-S00 nm) was not effective in preventing oedema injury. A far-red abaxial treatment during the light period tended to reduce the amount of injury that developed when photosynthetic photon flux was low (130-170 μmol·m-2·s-1), but this inhibition of the injury was absent with higher photon flux. The results from these studies indicate the use of supplemental far-red radiation treatments in greenhouses would not be justified because adequate and consistent control of the injury on ivy geraniums was not achieved.

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Terri Woods Starman and Shane Abbitt

The objective was to distinguish between series of cultivars of Pelargonium xhortorum (zonal geranium), Pelargonium hybrids (seed geranium), and Pelargonium peltatum (ivy leaf geranium) using DNA amplification fingerprinting (DAF) demonstrating the utility of DAF for patent protection to prevent infringement of inventor's rights. Leaf tissue of 10 plants of each cultivar of seedling geranium was bulked for DNA extraction, and cutting and ivy geranium cultivars were bulks of five plants of each cultivar. Isolated DNA from different cultivars of a series were bulked together in their respective series. Seedling geranium series included Dynamo, Glamour, Multibloom, Orbit, Pinto, and Ringo 2000. Cutting geranium series included Designer and Showcase. Ivy geraniums were from the Guillou group. Amplification was with one of two octamer primers, followed by reamplifying with one of four different mini hairpin primers. Gels were visually scored for presence or absence of bands. The four primers generated 336 bands. The average number of bands (_1000 bp) per primer was 40. Twenty percent of bands were polymorphic and distinguished between each series of cultivars. Genetic relationships were evaluated by SAHN cluster analysis based on the distance estimator of Dice using the NTSYS-pc program (Numerical taxonomy and multivariate analysis system, version 1.8). Series were grouped according to species. Seedling geraniums were in one large group, the two cutting geraniums were grouped together and the ivy leaf geraniums were a separate branch.

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Ritu Dhir, Richard L. Harkess, and Guihong Bi

The development of bleaching of the youngest leaves of actively growing ivy geranium (Pelargonium peltatum) has been observed as the season progresses from late spring to summer. Cultivar differences in foliar bleaching in response to elevated air temperature were studied. Ivy geranium ‘Beach’ and ‘Butterfly’ were grown in media containing sphagnum peat and perlite (70:30 v/v) for 6 weeks in modified greenhouse chambers with air temperatures averaging 28/16 or 36/22 °C (day/night). ‘Beach’ had greater plant width, growth index, leaf area, total fresh weight, and total dry weight than ‘Butterfly’ regardless of temperature. Overall, elevated air temperatures severely reduced plant width, plant growth index, leaf area, fresh weight, and dry weight of ivy geraniums. Elevated air temperatures caused foliar bleaching in both cultivars; however, ‘Butterfly’ was more susceptible to bleaching than ‘Beach’. ‘Beach’ had higher chlorophyll (Chl) b and total Chl content than ‘Butterfly’ at ambient air temperature, but they were similar at elevated air temperatures. Regardless of temperature, ‘Beach’ had greater Chl a, carotenoids (Caro), and pheophytins content but lower Chl a:Caro, Chl b:Caro, and total Chl:Caro ratios than ‘Butterfly’. This may contribute to the lower susceptibility to bleaching of ‘Beach’. Elevated air temperatures reduced Chl a, Caro, Chl a:Caro, Chl b:Caro, total Chl:Caro, and pheophytins content of ivy geraniums. In both cultivars, manganese (Mn) content increased with elevated air temperatures, but ‘Beach’ had greater Mn content than ‘Butterfly’. Total iron (Fe) content did not vary with cultivar or temperature. Irrespective of temperature, zinc (Zn) content was greater in ‘Beach’ than ‘Butterfly’, and irrespective of cultivar, Zn content was greater at elevated air temperatures. These results suggest greater chlorophyll, carotenoids, pheophytins, foliar Mn, and Zn contents play a role in reduced susceptibility of ‘Beach’ to foliar bleaching.