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Andrew Riseman, V.A. Sumanasinghe, Douglas Justice, and Richard Craig

We propose the name Exacum Styer Group for an interspecific population derived from several Sri Lankan Exacum taxa. Confirmation of hybrid status was determined by the appearance of either unique trait combinations or intermediate forms of traits originally represented by individual native taxa. Through 12 sexual generations, the proposed cultivar-group continues to exhibit these unique traits and now forms a cohesive fertile population.

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Hye-Ji Kim, Richard Craig, and Kathleen M. Brown

Ethylene induces significant petal abscission in regal pelargonium (Pelargonium ×domesticum L.H. Bailey). Three genotypes, `Elegance Silver' and its progeny, 00-43-1 and 00-43-2, were developed with exceptional production and postproduction characteristics. These genotypes had significantly enhanced individual floret longevity and whole plant longevity, and displayed more than twice as many florets as commercial cultivars. Dose response analysis demonstrated that `Elegance Silver' has reduced ethylene responsiveness throughout floret development, shown by lower petal abscission than other cultivars over a range of ethylene concentrations. Floret longevity was strongly correlated with ethylene responsiveness as indicated by S50 (ethylene concentration for 50% petal abscission), but not with ethylene production. These results suggest that reduced ethylene responsiveness is an important determinant of enhanced postproduction performance in the superior genotypes of regal pelargonium.

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Richard Grazzini, David Hesk, Ellen Yerger, Diana Cox-Foster, June Medford, Richard Craig, and Ralph O. Mumma

Biochemical and morphological components of 16 Pelargonium species and the P. ×hortorum interspecific complex were examined. Inflorescences and leaves of each species were analyzed for anacardic acids and the presence of glandular trichomes. Three species of the section Ciconium, P. acetosum, P. frutetorum, and P. inquinans, produced anacardic acids in association with glandular trichomes. only P. inquinans and P. frutetorum contained ω5- anacardic acids. An evolutionary model for the origin of anacardic acids and ω5- desaturation is proposed.

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Richard Grazzini, David Hesk, Ellen Yerger, Diana Cox-Foster, June Medford, Richard Craig, and Ralph O. Mumma

Composition of anacardic acids (phenolic acids known to be associated with small pest resistance in Pelargonium ×hortorum) was examined in 13 diploid and 25 tetraploid cultivars by high-performance liquid chromatography (HPLC). The presence of an unusual desaturation (omega (ω)-5) in the alkyl tail of anacardic acids present only in glandular trichome exudate of pest-resistant diploid inbred lines had previously been associated with a sticky-trap pest-resistance phenomenon. In this study, we examine Pelargonium cultivars for variability in anacardic acid composition to assess the distribution of ω5 desaturation among commercial cultivars, to determine possible interactions between ω5 desaturation and other plant desaturation mechanisms, and to examine the possible impact of ploidy on ω5 desaturation. An unsaturation index (UI) is derived to compare exudates differing widely in composition yet which may provide a similarly effective sticky-trap pest-resistance mechanism based on exudate viscosity. ω-5 Anacardic acids were observed in the glandular trichome exudate of all 38 commercial cultivars examined. No diploid cultivar produced ω5- and ω9- anacardic acids, although the simultaneous production of ω5 and ω9- anacardic acids was observed in three tetraploid cultivars. Total ω5- anacardic acids comprised from 42.4% (tetraploid cultivar Perlenkette-syn. Snowhite, Weiss) to 86.8% (tetraploid cultivar Amanda). Commercial P. ×domesticum cultivars had no ω5 anacardic acids. UIs ranged from 60.9 (tetraploid cultivar Dixieland) to 103.4 (diploid cultivar Pinto White). In contrast, anacardic acids collected from a pest-susceptible inbred line contained no ω5- anacardic acids and had a UI of 38.7. No significant differences among ploidy levels were observed for UIs or for most specific anacardic acid components, with the exception of 24:1 ω5- anacardic acid, in which the mean diploid value (32.1%) was significantly higher than that of the mean tetraploid value (27.6%). We conclude that ω5- anacardic acid production occurs in all Pelargonium cultivars observed and that these cultivars are predicted to exhibit resistance to small arthropod pests. Significant genetic variability in specific anacardic acid composition appears to exist among Pelargonium cultivars, suggesting that breeding for pest resistance can be readily monitored by HPLC of anacardic acids.

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Richard Grazzini, Donald Walters, Jody Harmon, David J. Hesk, Diana Cox-Foster, June Medford, Richard Craig, and Ralph O. Mumma

Diploid zonal geraniums (Pelargonium ×hortorum) are able to resist attack by small arthropod pests such as the two-spotted spider mite (Tetranychus urticae Koch) when exudate produced by tall glandular trichomes contains a high percentage of ω5-unsaturated anacardic acids. Trichomes of susceptible plants exude primarily saturated anacardic acids. Inbred mite-resistant and -susceptible geraniums were reciprocally crossed and the F1, F2, and backcross generations were examined for anacardic acid composition and trichome density. Selected F2 plants were bioassayed for resistance to two-spotted spider mites. High concentrations of ω5-unsaturated anacardic acids in resistant plants are conditioned by a single dominant allele. We propose that inheritance of tall glandular trichome density can be controlled by a small number of loci (possibly as few as one) exhibiting codominance. F2, with low densities of tall glandular trichomes and producing ω5-unsaturated anacardic acids, displayed effective resistance to two-spotted spider mites as measured by mite mortality and fecundity. A genetic model for the biosynthesis of anacardic acids is proposed.

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Richard L. Bell, Tom van der Zwet, Roland C. Blake, Craig K. Chandler, and Joseph C. Scheerens

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C. Frederick Deneke, Leon J. Glicenstein, Kathleen B. Evensen, and Richard Craig

The postproduction quality of 33 cultivars and 178 Pennsylvania State Univ. breeding lines of Pelargonium ×domesticum L.H. Bailey was evaluated in a simulated consumer environment. Petal abscission was the primary factor that reduced postproduction ratings (PPR). The heterozygosity of some cultivars was indicated by the range of PPR of progeny from self-pollinations. This range of PPR implies that P. ×domesticum has genetic variation for postproduction quality that can be used in a breeding and selection program. Few progeny with high PPR were produced from either self- or cross-pollinations involving parents with low PPR. Many of the superior progeny resulted from parents with high PPR. Therefore, progeny with improved postproduction quality can be developed by selecting parents with high PPR.

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Neil V. O'Connell, Craig E. Kallsen, Richard L. Snyder, Blake L. Sanden, Paul W. Giboney, and Mark W. Freeman

Many citrus growers are hesitant to plant cover crops, particularly perennial types, because of possible increased frost hazard. To quantify the increased risk, temperature relations over a 3-year period were compared between areas in a `Valencia' orange orchard with and without a partial perennial cover crop. The partial perennial cover crop consisted of a mowed perennial planting along the double drip line hoses, and an annually fall-replanted unirrigated strip of groundcover in the middle between the tree rows. This partial perennial cover crop increased the frost hazard compared to uncultivated bare ground even when wind machines were operating.

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Rose E. Palumbo, Wai-Foong Hong, Jinguo Hu, Charles Krause, James Locke, Richard Craig, David Tay, and Guo-Liang Wang

Pelargonium is one of the priority genera collected by the Ornamental Plant Germplasm Center (OPGC). In order to protect future breeders from a loss of genetic diversity, the OPGC collects heirloom cultivars, breeding lines, and wild species. The current Pelargonium collection consists primarily of cultivars originating from P. ×hortorum and P. ×domesticum. Our project was designed to analyze the current collection in order to facilitate the maintenance of a more-diverse core collection. We have expanded our TRAP (Target Region Amplified Polymorphism) analysis from 120 plants with one primer set to include 780 plants with four primer sets. Each primer set consists of a labeled arbitrary primer paired with a gene-specific primer, and two different fluorescent labels were used to allow multiplexed PCR reactions. We scored about 90 markers in each of the first two primer sets and about 60 markers in each of the second two. In comparisons between the phylogeny and the morphology and taxonomy of these plants, we show some matching clusters that may be explained by the breeding history of the plants.

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Rose Palumbo, Wai-Foong Hong, Guo-Liang Wang, Jinguo Hu, Richard Craig, James Locke, Charles Krause, and David Tay

Pelargonium was a priority genera collected by the Ornamental Plant Germplasm Center (OPGC) until a recent reorganization. To preserve genetic diversity for future breeders, OPGC collects heirloom cultivars, breeding lines, and wild species. The current Pelargonium collection at OPGC consists primarily of cultivars originating from P. ×hortorum and P. ×domesticum. Target region amplification polymorphism (TRAP) has the advantage of producing a large number of markers through use of sequence information that is already available. Our first goal was to determine the feasibility of TRAP for the analysis of this large collection, so that in the future the most diverse genotypes may be retained. To achieve this goal, we first modified existing DNA extraction techniques to account for the high levels of phenolic compounds present in some Pelargonium species by combining several washes to remove the phenolics with the addition of high levels of antiphenolic compounds. Second, we evaluated the TRAP procedure using the DNA isolated from 46 accessions. For 44 accessions, one or two primer combinations generated enough fragments to discriminate each of the accessions, and similar clades were produced by cluster analysis of the polymorphic fragments amplified by different primer combinations. All the scorable fragments were polymorphic, for one primer combination there were 148 markers from one image and the other produced 160 markers on two images. These results demonstrate that TRAP is an effective method for molecular characterization of ornamental collections.