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  • Author or Editor: Guo-Liang Wang x
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The Ornamental Plant Germplasm Center (OPGC) maintains a collection of herbaceous ornamental plants in order to protect future breeders from a loss of genetic diversity. The current Pelargonium collection includes ≈870 accessions. Our preliminary studies showed that TRAP (Target Region Amplified Polymorphism) has promise for analyzing the variation in our collection, and so we have expanded the study to analyze the entire Pelargonium collection. We have used the same primers for this screening of the Pelargonium collection as were used on sunflowers, and TRAP results run on a sequencing gel showed 90–150 bands that segregate the population into groups of similar accessions. In order to facilitate analysis of OPGC's large population, we have converted the method to a high throughput technique that efficiently analyzed the entire population. We used a 96-well DNA extraction kit from Qiagen that produced high quality DNA in spite of the high phenol levels in some Pelargonium species. Also, the use of labeled primers allowed analysis of the gels to be aided by a computer. These results produce a categorization of the collection that, combined with morphology and taxonomy, will form the basis for future studies that will use target genes specific to Pelargonium.

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Triploid loquat (2n = 3x = 51) has stronger growth vigor and larger leaves, flowers, and fruit compared with its diploid parental plant (2n = 2x = 34), but the effects of triploidization on the contents of flavonoids and phenolics in leaves and flowers, which are the most important antioxidant compounds for pharmacological applications, have not been reported. In this report, 58 triploid loquat genotypes and seven corresponding diploid parental cultivars were used to evaluate the effects of triploidization on the contents of total flavonoids and phenolics and the antioxidant activities of leaves and flower buds. The results showed that the contents of total flavonoids and phenolics and their corresponding antioxidant activities were higher in most of the triploid loquat genotypes than their diploid parents. The antioxidant activities of leaves and flower buds were significantly correlated with the total flavonoids and phenolics contents in both diploid loquat and triploid loquat. It could be inferred that triploidization could increase the contents of flavonoids and phenolics in leaves and flower buds of loquat. Notably, the contents of total flavonoids and phenolics of leaves in triploid genotype ‘H3/24’ were the highest, reaching 212.00 mg rutin equivalent (RE)/g DW and 93.06 mg gallic acid equivalents (GAE)/g DW, respectively, which were significantly higher than those previously reported. Such a valuable trait may be stacked with other triploid traits that are already established, such as larger vegetative organs and better tolerance to various stresses, as a feasible strategy for breeding loquat cultivars with high pharmaceutical potency.

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Amplified fragment length polymorphism (AFLP) analyses were used to assess genetic diversity among 30 genotypes of watermelon [Citrullus lanatus (Thunb.) Mansf.] representing a broad genetic base, including breeding lines and commercial germplasm. Eight AFLP primer combinations selected from 64 primer combinations were polymophic. The polymorphism was 13.0% to 31.9% within the 28 cultivars examined, and 45.3% to 64.2% among all the genotypes. Each genotype could be successfully distinguished based on AFLP scoring. Cluster grouping of accessions based on the AFLP analysis was consistent with that from classification by pedigrees and ecotypes.

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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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Pelargonium is one of the important flower crops in USA. It is a priority genus for conservation at the USDA Ornamental Plant Germplasm Center (OPGC). It belongs to Geraniaceae family and comprises of about 280 species. To understand the genetic variation of the Pelargonium collection at OPGC, the PCR-based TRAP (target region amplified polymorphism) marker system which was newly developed in sunflower was used in this study. Twelve sets of primers were used to fingerprint 46 accessions representing 21 commercial P. hortorum, 17 scented geraniums and 8 other unidentified Pelargonium taxa. About 150 DNA bands could be detected in each primer and accession combination. Cluster analysis showed that molecular data was highly correlated with the phenotypes. Cultivars with similar morphological traits were clustered together. These results demonstrated that the TRAP system is a useful technique for the characterization and classification of Pelargonium collections.

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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.

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This study examined the ability to vegetatively propagate 1-year-old pecan (Carya illinoinensis) through the rooting of hardwood cuttings. Cuttings were treated with varying concentrations of different auxins and different combinations of media and ambient temperatures. Under different temperature conditions, all auxin treatments induced the rooting of cuttings but did not promote sprouting. The effectiveness of the induction of adventitious roots was as follows: 1-naphthalene acetic acid (NAA) > indole 3-butyric acid > indole 3-acetic acid. The base of the parent shoot treated by NAA at a concentration of 0.09%, planted in substrate with bottom heat was the most effective, with 82% rooting, 8.3 roots/cutting and root lengths of 7.3 cm. These findings suggested that auxin and substrate/air temperature differences are both indispensable in the process of adventitious roots formation in pecan. This study revealed that the propagation of hardwood cuttings derived from branches of 1-year-old pecan is possible.

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