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Robert G. Fjellstrom and Dan E. Parfitt

RFLPs were studied in 41 populations of 13 Juglans species to study genetic diversity and phylogenetic relationships. 19 single locus nuclear RFLP loci were used to generate genetic distance/identity matrices based on allele frequencies. 21 probes were used to generate genetic distances and phylograms using shared-fragments with parsimony analysis. Parsimony analysis on fragment data produced a minimal length tree in general agreement with distance data trees, but with additional phylogenetic resolution resembling previous systematic studies. All analyses indicate an ancient origin of J. regia, which has been considered a recently derived species. A 10x difference in heterozygosity was seen among species. Genetic differentiation among conspecific east Asian populations was larger than among east Asian species. The opposite was true for American species. J. hindsii is classified as a distinct species and J. cinerea was included in section Cardiocaryon rather than Trachycaryon, from the diversity analysis.

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Tehryung Kim and Hazel Y. Wetzstein

It has been shown that perennial woody plants exhibit marked seasonal changes in nutrient content, carbon metabolism, and organ development. A knowledge of seasonal nutrient allocation and temporal accumulation patterns can be useful in the development of fertilization regimes that reflect the biology of a tree crop. Maintenance of optimum leaf nutrient status is an important priority in pecan cultural practice. However, a systematic evaluation of nutrient resorption is lacking in pecan. In this work, seasonal changes in nutrients and carbohydrates were evaluated in pecan trees grown under orchard conditions. In addition, resorption efficiencies of eight pecan cultivars were evaluated. Significant levels of resorption were observed in all essential elements, but cultivar differences were not significant. Seasonal patterns of nutrient and carbohydrate content in leaf, stem, and shoot tissue, will be presented as well as a structural evaluation of abscission zone formation.

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Zhang Deshun and Jia Xiangyun

Taking Beihua shan and Wuling shan mountain as examples, the author investigated the Wild Ornamental Plants (WOP) resources in mountain area of northern China in detail with ecological systematic sampling method. The meteorological data of no meteorological observed plots was reckoned theoretically using statistics. And then the main factors that influence the WOP distribution were sifted out by the progressive regression analysis. At last the optimized chains of adaptability with which the WOP will be introduced from mountain to urban area and of most suitable place on which certain plants will be introduced were defined. In order to enrich the capital Beijing's afforestation materiels, this paper offers a reliable basis in terms of theory.

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Chengyan Yue, Jingjing Wang, Eric Watkins, Stacy A. Bonos, Kristen C. Nelson, James A. Murphy, William A. Meyer, and Brian P. Horgan

The development and evaluation of new turfgrass cultivars require considerable resources. A systematic understanding of the breeders’ and distributors’ trait selection behavior can provide a basis for making adjustments and improvements based on industry needs and thus accelerate the breeding process and make it more efficient. The objective of this study is to investigate the selection priorities for turfgrass traits and identify the most influential factors affecting turfgrass breeders’ and distributors’ likelihood of selecting turfgrass traits. Results show that the most important trait clusters for both breeders and distributors were abiotic stress resistance and growth characteristics. Breeders were more likely than distributors to select appearance traits when setting trait priorities. Program characteristics such as program size, education level, and being a male respondent had positive effects on the reported likelihood of selecting studied turfgrass traits, and these effects varied for different trait clusters.

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A.M. Armitage and Meg Green

The University of Georgia trial garden has been in existence since 1982, and the method of evaluation and distribution of taxa has evolved over the years. Annual and perennial taxa are evaluated systematically, over the entire season, providing season-long summaries for each one. Annuals are evaluated every 2 weeks, and scores are based on plant performance, including foliar health, flower numbers and the appearance of disease and insect damage. Perennials are evaluated similarly, however flowering time, flowering persistence and height in the landscape are also noted. Summaries for each taxon are presented in tabular and graphic form. Many new crops have been evaluated and introduced to the floriculture industry. New crops are placed in the horticulture gardens and evaluated by garden personnel and by commercial growers and landscapers. Plants have been distributed free of charge to propagators and growers, resulting in rapid market acceptance of successful taxa.

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Li-Hong Gao, Mei Qu, Hua-Zhong Ren, Xiao-Lei Sui, Qing-Yun Chen, and Zhen-Xian Zhang

Single-slope, energy-efficient solar greenhouses in China use solar energy as the sole source of light and heat for winter crop production in the region between latitudes 32°N and 43°N. The use of solar greenhouses has greatly reduced energy demand and carbon dioxide (CO2) emissions. Solar greenhouses are the best structure for growing winter horticultural crops in China, and have been adopted by countries such as Japan, Korea, and Russia. Increased proliferation of efficient solar greenhouses in China may contribute to solving worldwide problems such as the energy crisis and global climate change. This article summarizes the structure, function, application, and ecological benefits of energy-efficient, single-slope solar greenhouses in China, based on 20 years of systematic studies. We hope this technology can be applied to regions of similar climate to help reduce energy consumption and CO2 emissions.

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Thomas E. Marler and Leah E. Willis

We are grateful to C. Hubbuch for systematic guidance in defining the list of species for this survey and to P. Andersen, B. Dehgan, and T. Walters for evaluation and suggestions for improving the manuscript. The cost of publishing this paper was

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John L. Maas, John M. Enns, Stan C. Hokanson, and Richard L. Hellmich

1 Research Plant Pathologist. 2 Horticulturist. 3 Research Geneticist. 4 Research Entomologist. We are grateful to M. Alma Solis, Research Entomologist, Systematic Entomology Laboratory. ARS. USDA, Beltsville, for insect identifications, and

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J.B. Magee, B.J. Smith, and Agnes Rimando

Control of muscadine diseases is necessary to minimize yield loss and is especially important for highest quality if the berries are to be marketed fresh. Throughout the 1998 growing season, vines of five muscadine cultivars (`Noble', `Summit', `Cowart', `Higgins', and `Carlos') were treated under a systematic disease control spray program; four fungicides registered for use on grapes were applied sequentially at 10- to 20-day intervals from early bloom until just before harvest. Control plants received no fungicide. The objectives of the study were to determine the effects of the spray schedule on foliage and berry diseases and to study the relationship between disease incidence and resveratrol content of the berries. Resveratrol is a phytoalexin and has been favorably implicated in cardiovascular disease and certain cancer processes. Foliar diseases were rated visually twice during the season. Berry disease ratings were made at harvest. All fungal foliage and berry diseases were significantly reduced by the fungicide treatments. Resveratrol concentrations were determined separately on berry skins, seed and pulp/juice by GC/MS. Overall, resveratrol levels in berry skins from unsprayed vines were much higher than those of sprayed vines. Concentrations varied by cultivar and within cultivar by treatment. The relationship of skin concentration and total disease score or scores of specific diseases has not been established. Seed resveratrol concentrations differed by cultivar but were not affected by the fungicide treatments. Mean concentration of seed was lower than that of skins. Accumulation of resveratrol in juice/pulp was much lower than in skins and seeds.

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Hirofumi Terai, Alley E. Watada, Charles A. Murphy, and William P. Wergin

Structural changes in chloroplasts of broccoli (Brassica oleracea L., Italica group) florets during senescence were examined using light microscopy, scanning electron microscopy (SEM) with freeze-fracture technique, and transmission electron microscopy (TEM) to better understand the process of chloroplast degradation, particularly at the advanced stage of senescence. Light microscopy revealed that chloroplasts, which initially were intact and green, became obscure in shape, and their color faded during senescence. Small, colored particles appeared in cells as the florets approached the final stage of senescence and became full- to dark-yellow in color. Scanning electron microscopy showed that stroma thylakoids in the chloroplast initially were parallel to each other and grana thylakoids were tightly stacked. As senescence advanced, the grana thylakoids degenerated and formed globules. The globules became larger by aggregation as senescence progressed, and the large globules, called “thylakoid plexus,” formed numerous vesicles. The vesicles ultimately were expelled into the cytosol, and the light microscope revealed many colored particles in the senescent cells. These results indicate that the degradation of chloroplasts in broccoli florets progresses systematically, with the final product being colored particles, which are visible in yellow broccoli sepal cells.