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Douglas A. Hopper and Kevin T. Cifelli

Growth predictions derived from data collected in controlled-environment chambers would be expected to differ from growth responses observed in variable greenhouse conditions. ROSESIM was developed as a dynamic plant growth model based on `Royalty' rose (Rosa hybrida L.) response to 15 unique treatment combinations of photosynthetic photon flux (PPF), day temperature (DT), and night temperature (NT) under constant growth chamber conditions. Regression coefficients for growth equations are read from an external ASCII file, thus permitting coefficients up to a full quadratic model form. Calibration coefficients (CC) were added to ROSESIM to enable predictions to be altered proportionally to permit improved prediction of specific growth characteristics. Numerator and denominator values for CC are adjustable for the first 10 days (initial) growth equations, subsequent growth until anthesis equations, and for the prediction of anthesis. Validation studies were used to set CC values; this enables the model based on growth in controlled environment chambers to be systematically calibrated on site to fit actual growth measured at a specific greenhouse location.

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Alan T. Bakalinsky, Hong Xu, Diane J. Wilson, and S. Arulsekar

A total of eight random amplified polymorphic DNA (RAPD) markers were generated in a screen of 77 primers of 10-base length and were detected reproducibly among nine different grape (Vitis) rootstocks. Occasional failed amplifications could not be explained rationally nor easily corrected by systematic replacement of individual reaction components. In an effort to improve their reliability, the RAPD markers were cloned, their termini sequenced, and new sequence-specific primer pairs were synthesized based on addition of 10 to 14 bases to the 3' termini of the original 10-mers. Six pairs of the new primers were evaluated at their optimal and higher-than optimal annealing temperatures. One primer pair amplified a product the same size as the original RAPD marker in all rootstocks, resulting in loss of polymorphism. Post-amplification digestion with 7 different restriction endonucleases failed to reveal restriction site differences. Three primer pairs amplified an unexpected length variant in some accessions. Two other pairs of primers amplified a number of unexpected bands. Better approaches for exploiting the sequence differences that account for the RAPD phenomenon will be discussed.

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Philip L. Forsline, Warren F. Lamboy, James R. McFerson, and Cecil Stushnoff

The USDA–ARS germplasm collection of cold-hardy Vitis held at the Plant Genetic Resources Unit, Geneva, N.Y., has over 1300 clonal accessions maintained as field-grown vines. Security back-up using field-grown or potted vines at remote sites or via in vitro methods is costly. Cryopreservation offers a safe, cost-effective alternative. While we routinely employ cryogenic storage of dormant buds of Malus, dormant buds of Vitis generally do not appear to tolerate the desiccation levels required by our current cryopreservation protocol. Since tolerance to desiccation and cold appear to be correlated in Vitis, we tested desiccation tolerance of 60 germplasm accessions selected from the core subset to represent a range of cold hardiness. Budwood was collected in December 1995 in Geneva, stored at –4°C in sealed bags, and systematically desiccated to 30% and 20% moisture. In some treatments, additional desiccation was imposed by slow freezing to –25°C. Microscopic examination of rehydrated buds indicated 60% of accessions tolerated desiccation as low as 20% moisture. Freeze-desiccation at –25°C after desiccation at –4°C neither increased nor decreased viability in these accessions. Only slight modification so current protocols should be necessary for cryopreservation of this class. Of the remaining accessions, 25% tolerated desiccation to 30% moisture, but 15% were intolerant to any desiccation level tested. Techniques must be developed to successfully cryopreserve both these classes of accessions.

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Thomas Ranney* and Thomas Eaker

Information on ploidy levels is extremely valuable for use in plant breeding programs. Fertility, crossability, and heritability of traits are all influenced by ploidy levels. Knowledge of reproductive pathways, including occurrence of apomixes, pseudogamy, and formation of unreduced gametes can also be important information for developing breeding strategies. Although ploidy level can be determined by counting chromosomes, flow cytometry provides a reliable and much faster means for determination of nuclear DNA content and associated ploidy level. Measurement of ploidy levels of seeds (embryo and endosperm) can also provide useful insights into reproductive pathways. The objective of this study was to determine the approximate genome size, estimated ploidy level, and range of reproductive pathways of a diverse collection of flowering crapbapples (Malus spp.). Genome sizes were calculated as nuclear DNA content for unreduced tissue (2C). Results from the taxa included in our survey showed DNA contents ranging from 1.52 to 1.82 for diploids, 2.40 to 2.62 for triploids, and 3.36 to 3.74 pg/2C for tetraploids. Based on these ranges, we identified 43 diploid, 10 triploid, and 4 tetraploid crabapple taxa in this collection. Results from open pollinated seeds and seedlings demonstrated a variety of reproductive pathways including apomixes and unreduced gametes. This research provides information on ploidy levels and reproductive pathways of flowering crabapples and will allow for more systematic and efficient progress in the development of improved cultivars.

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Todd Rosenstock and Patrick Brown

Alternate bearing exerts economic and environmental consequences through unfulfilled yield potential and fertilizer runoff, respectively. We will discuss a systematic biological–statistical modeling management integration approach to address the concert of mechanisms catalyzing alternate bearing. New engineering technologies (precision harvesting, spatially variable fertigation, and mathematical crop modeling) are enabling optimization of alternate bearing systems. Four years of harvest data have been collected, documenting yield per tree of an 80-acre orchard. These results have shown variability within orchard to range from 20–180 lbs per tree per year. Results indicate irregular patterns not directly correlated to previous yield, soil, or tissue nutrient levels, or pollen abundance. Nor does significant autocorrelation of high or low yields occur throughout the orchard, suggesting that genetically dissimilar rootstocks may have significant impact. The general division of high- and low-yielding halves of the orchard may infer a biotic incongruency in microclimates. This orchard does not display a traditional 1 year-on, 1 year-off cyclic pattern. Delineation of causal mechanisms and the ability to manage effectively for current demands will empower growers to evaluate their fertilization, irrigation, male: female ratio, site selection, and economic planning. In comparison to annual crops, the application of precision agriculture to tree crops is more complex and profitable. When applied in conjunction, the aforementioned methods will have the ability to forecast yields, isolate mechanisms of alternate bearing, selectively manage resources, locate superior individuals, and establish new paradigms for experimental designs in perennial tree crops.

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C. Richer-Leclerc and J.-A. Rioux

The “Réseau d'esssais des plantes ligneuses ornementales du Québec” (REPLOQ) is a research project initiated in 1982 with the mandate to elaborate, develop and coordinate a cooperative research project to evaluate the winter hardiness of ornamental plants. Systematic evaluation trials provided information on growth potential and hardiness of woody trees and shrubs evaluated over a five year period in the principal growing regions of Québec. Zonal range covered was 2 to 5b in the Canadian system. Adequate field testing is critical for new introductions and, since 1984, more than 400 species and cultivars have been introduced in 8 evaluation sites. Results were published on several forms: technical factsheets provide cultural and production recommendations for the species and cultivar evaluated in each climatic zone. Propagation methods as well as their potential for ornamental purpose were described. In the 1984 plantation, Malus baccata and Quercus macrocarpa showed a similar potential for acclimation, but Malus baccata could be produced advantageously in any area, while the production potential of Quercus macrocarpa was enhanced by the summer heat of the wannest region. In this group of plants, Acer saccharinum was the species with the greatest number of plants suffering winter damage and could not be grown without risk anywhere in the area studied. Acer platanoides was severely damaged in the coldest of the eight evaluation sites and should not be cultivated there.

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Elsa Sanchez and Richard Craig

The Plant Systematics course at Penn State University was reformatted in 1995 based on a three-dimensional model. It now includes several collaborative learning activities: a learning fair hosted by the enrolled students for elementary school students; applied laboratory exercises; and applied laboratory examinations. Each activity has a specific objective and was constructed to strengthen teaching effectiveness and to aid students in developing useful skills for future employment. A survey was administered to students enrolled in the course from 2003 through 2005 in part to assess the collaborative learning activities. Most students “strongly agreed” or “agreed” that they liked working in collaborative groups and learned from other group members. Students preferred working in groups for laboratory examinations more than for the Asteraceae Fair and learned more from their peers while completing the laboratory exercises than in laboratory examinations. Student participation in the lecture portion of the course increased as collaborative learning activities were completed. Camaraderie with peers through group work may have created an atmosphere conducive to participation and/or involvement during lectures. Organization and planning were vital to the success of these activities, as were using small groups and providing adequate incentives for completing activities. These activities engaged students to become active participants in the teaching and learning process.

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Timothy J. Smalley and Frank B. Flanders

The Industry Liaison Committee of the American Society for Horticultural Science conducted a survey of the horticulture industry to systematically determine: 1) industry's perception of university training of recent graduates and 2) industry's perception of educational needs for future graduates. A Delphi survey was sent to experts in the fruit, ornamental, greenhouse, turf, and vegetable industry. The respondents expressed dissatisfaction with the level of competence of recent university graduates in personnel management and marketing. The lack of hands-on training in university courses was viewed as a major problem, but the respondents agreed that internships should provide university students with the necessary practical experience and universities should concentrate on the science of horticulture. The respondents indicated that business management and marketing expertise will be more important in the future than knowledge of production techniques; however, they would not be more likely to hire a business major instead of a horticulture major. The following areas of study were ranked for relative importance to be included in the university curriculum (from most important to least): communication skills, horticultural technology, business management, personnel management, plant nutrition and soil fertility, pest control, plant physiology, environmental awareness, plant physiology, plant pathology, accounting, and equipment use and maintenance. A second round of questioning for this Delphi survey is being conducted and results will be presented to verify preliminary results.

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Sandra B. Wilson, Robert L. Geneve, and Fred T. Davies

Interactive web-based questions were developed for students to review subject matter learned in an online plant propagation course. Articulate Storyline software was used to build nearly 250 review questions with five different testing styles to ascertain proficiency in subject areas, including the biology of propagation, the propagation environment, seed propagation, vegetative propagation, micropropagation, and cell culture. Questions were arranged to correspond to the supporting textbook chapters in Hartmann and Kester’s Plant propagation: Principles and practices, ninth edition. These are open access and available to instructors and students worldwide. Users received immediate feedback for each question answered correctly or incorrectly. The system remembers where one leaves off, which enables starting and stopping multiple times within a chapter. Means of pre- and posttest responses to nine content knowledge items showed that students perceived a significant content knowledge gain in the course. These online interactive reviews can be adapted easily to other courses in a variety of fields, including horticulture, botany, systematics, and biology. They can also be expanded to overlay multiple objects and trigger events based on user response. Since inception, the website hosting these online reviews averaged 156 unique visitors per month. Students have reported this to be a useful tool to prepare them for course exams.

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M.H. Maletta, W.P. Cowgill Jr., T. Manning, W. Tietjen, S.A. Johnston, and P. Nitzsche

Weather information has many applications in crop production practices, including disease forecasting. A variety of weather instruments are available for on-farm use, but associated costs and need for regular calibration and maintenance can limit actual use, especially by smaller growers. Subscription to an electronic meteorological service may be a viable alternative to on-site weather stations. In 1997 and 1998, hourly temperature, relative humidity and leaf wetness were monitored at six sites in a 400-m2 area of New Jersey with Field Monitor™ data loggers (Sensor Instruments, Inc.) and by subscription to SkyBit, Inc., an electronic meteorological service. There was close correspondence in temperature data from the two sources at all sites, the average seasonal difference ranging from 0 to 2 °F. Relative humidity data was variable between the two sources, the greatest variation occurring at low and high humidity, the ranges at which relative humidity sensors had been shown to be least accurate. Leaf wetness estimates from the two sources agreed at least two-thirds of the time. Data differences related to source were attributed to both systematic and random error. The usefulness of electronic weather data in crop production depends on how sensitive the particular weather-dependent applications (e.g., predictive disease and insect models) are to variation in the input data. The TOM-CAST early blight forecaster for tomatoes was not particularly sensitive to differences between SkyBit and Field Monitor leaf wetness estimates.