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Stan C. Hokanson, Phil L. Forsline, James R. McFerson, Warren F. Lamboy, Herb S. Aldwinckle, and Aimak D. Djangaliev

Malus sieversii, the main progenitor of domesticated apple, is native to areas in Central Asia. To better represent Malus wild germplasm in the USDA–ARS germplasm collections, maintained in Geneva, N.Y., a cooperative project was initiated with the Republic if Kazakhstan to collect and assess that country's wild populations of M. sieversii and to develop more secure in situ reserves to complement ex situ holdings in the United States and Kazakhstan. To date, four exploration trips to the region have included participants from the United States, Kazakhstan, Canada, New Zealand, and South Africa. Four Kazkh scientists have toured USDA–ARS sites, exchanged information, and collected germplasm in the United States greenhouse screens of 1600 have revealed potentially new sources of resistance to apple scab, cedar apple rust, and fire blight. An isozyme analysis of maternal half-sib families from four regions suggests the populations of M. sieversii collected represent a single panmictic population, with over 85% of total genetic variation due to differences among families. The most recent collections in 1995 were directed towards more ecologically diverse regions, including a site (Tarbagatai) at the most northern limit for M. sieversii equivalent to northern Minnesota in the United States. Some trees in this region produced fruit nearly 70 mm in diameter with excellent aroma, firmness, and color. This germplasm is being systematically characterized for horticultural traits, pest and disease resistance, and molecular markers.

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Marietta Loehrlein and Sandy Siqueira

Landscape and garden use of Coreopsisrosea has been growing recently. With the introduction of the new varieties of Coreopsisrosea `Sweet Dreams' and `Limerock Ruby', there are increased opportunities for commercial sales. While plants can be propagated by vegetative means, seed production is generally less expensive, seed can be stored, and hybrid development depends on seed production. As a result, it is beneficial to understand the reproductive process of the plant. The purpose of this research was to investigate the reproductive development of Coreopsisrosea. This research also seeks to identify, describe and record inflorescence morphological characters, which could be useful in plant systematic and phylogeny studies. To this end, the anthesis process of pink tickseed, Coreopsisrosea Nutt., was studied in 100 inflorescences from 10 plants. Inflorescences were tagged when they were first visible and measured daily for a month. The following measurements were taken: number of ray flowers, inflorescence diameter, diameter of the disc floret cluster (head), timing of anthesis, presence of pollen, and the longevity of opened flowers. The inflorescence anthesis process was 19.8 (±1.6) days long and was subdivided into 13 stages of development. During the 20 days of inflorescence anthesis, the flower was open 27.5% of the time (5.4 days). When the disc florets started to open, they did so from the outer layer of the cluster to the center of the cluster; therefore, florets in the head did not mature at the same time. Micrographs were taken using a dissecting microscope (Cobra dynascope) to illustrate the entire process.

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William W. Inman and William L. Bauerle

Recent work has shown that stomatal conductance (gs) and net photosynthesis (Anet) are responsive to the hydraulic conductance of the soil to leaf pathway (Xp). Two tree species with differing xylem structures were used to study the effect of systematic manipulations in Xp that elevated xylem hydraulic resistance. Simultaneous measures of gs, Anet, bulk leaf abscisic acid concentration (ABAL), leaf water potential (L), and whole plant transpiration (Ew) were taken under controlled environment conditions. Quercus shumardii Buckl. (shumard oak), a ring porous species and Acer rubrum L. `Summer Red' (red maple), a diffuse porous species, were studied to investigate the short-term hydraulic and chemical messenger response to drought. Both species decreased Anet, gs, L, and Ew in response to an immediate substrate moisture alteration. Relative to initial well-watered values, red maple Anet, gs, and Ew declined more than shumard oak. However, gs and Anet vs. whole-plant leaf specific hydraulic resistance was greater in shumard oak. In addition, the larger hydraulic resistance in shumard oak was attributed to higher shoot, as opposed to root, system resistance. The results indicate hydraulic resistance differences that may be attributed to the disparate xylem anatomy between the two species. This study also provides evidence to support the short-term hydraulic signal negative feedback link hypothesis between gs and the cavitation threshold, as opposed to chemical signaling via rapid accumulation from root-synthesized ABA.

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

The “Réseau d'essais 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 5-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 and eight evaluated in each climatic zone. Propagation methods, as well as their potential for ornamental purpose, were described. In the 1984 plantation, 30 ornamental species and cultivars were evaluated. Winter damage data observed on each plant during this period were analyzed by Clusters analysis and five groups of plants were determined. Trees, flowering shrubs, and foliage shrubs were discussed separately and winter damages of each group were submitted to “Correspondence analyses” to identify plant response to climatic conditions. Growth and production potentials were defined by SAS analysis. Hardiness zone of each species was detailed, established, or modified.

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A. Medlicott, J. Brice, T. Salgadol, and D. Ramirez

No systematic curing and storage techniques are currently used with onions in Honduras; postharvest losses occur rapidly. The objective of this study was to evaluate the use of storage bins (maximum capacity 7t) that use forced ambient air ventilation to manipulate the atmospheric conditions around the onions. The desired storage conditions were 26 to 30C and 60% to 75% relative humidity. Ventilation regimes were manipulated in an attempt to obtain these conditions. The rate of deterioration in four varieties of onions over a 3-month period was determined and compared with onions stored under normal ambient conditions. Marketable onions in the forced-air storage bin compared to the controls stored under ambient conditions after 13 weeks were 82% vs. 37% for `Granex 33'; 71% vs. 40% for `Granex 429'; 63% vs. 31% for `Granex 438'; and 90% vs. 44% for `Texas Grano 502'. This represents a significant increase in the number of marketable onions after storage. All losses were increased by rain and tornado damage after 1 month of storage. The methods used to maintain uniform temperature and humidity conditions in the storage bin are discussed together with the problems encountered. The construction and operating costs are given together with the market prices and the required returns to cover the bin costs.

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Samia Lotfy, Francois Luro, Françoise Carreel, Yann Froelicher, Delphine Rist, and Patrick Ollitrault

Somatic hybridization allows the creation of new patterns of nuclear, mitochondrial and chloroplastic association. It is therefore necessary to master cytoplasmic molecular markers to determine the genetic origin of both organelles of plantlets obtained from protoplasts fusion. In the case of Citrus and related genera, only southern blot hybridization and restriction fragment-length polymorphism (RFLP) techniques were used for this task until now. Here, we describe the use in the Aurantioideae subfamily, of a simple and non labeling cleaved amplified polymorphic sequence (CAPS) technique, to determine the cytoplasmic genome origin of intergeneric somatic hybrids. Mitochondrial and chloroplastic universal primers previously selected for population genetic studies in Quercus by Demesure et al. (1995) are used with some modifications. The variability of cytoplasmic genome among somatic fusion partners is detected by coupling amplification and restriction reactions. Digested DNA fragments are analyzed by agarose gel electrophoresis (PCR-RFLP). This technique has been applied for the analysis of the cytoplasmic constitution of somatic hybrids arising from intergeneric, intersubtribal and intertribal combinations. Systematic transmission of the mitochondria from protoplasts isolated from embryogenic callus parents was confirmed.

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E.H. Simonne, J.T. Eason, J.A. Pitts, and J.T. Owen

Bell pepper (Capsicum annuum L.) fruit are typically green in color at the immature stage, 1/3 and 2/3 colored during ripening, and red at maturity. However, this sequence does not apply to new varieties with immature colors of white or purple, intermediate colors of brown or black, and mature colors of yellow or orange. The study of physiological changes during ripening in such cultivars requires the description of color changes. Therefore, color changes of new bell pepper varieties were evaluated by subjective description and objective measurement of L, a, and b. Color changes were described with a five-color stage scale. L, a, and b were affected significantly by variety (P < 0.01), and a and b were affected significantly by color stage (P = 0.95, 0.01, and 0.01 for L, a, and b, respectively). Location and cultivar*location had no significant effect. For each cultivar, differences in a and b values defined color stages that were clearly identifiable. When plotted, color measurements (a and b) were in good agreement with the verbal descriptions. Therefore, measurements of L, a, and b are not systematically necessary when referring to bell pepper colors.

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S.S. Miller, R.W. McNew, B.H. Barritt, L. Berkett, S.K. Brown, J.A. Cline, J.M. Clements, W.P. Cowgill, R.M. Crassweller, M.E. Garcia, D.W. Greene, G.M. Greene, C.R. Hampson, I. Merwin, D.D. Miller, R.E. Moran, C.R. Rom, T.R. Roper, J.R. Schupp, and E. Stover

Cultivar and planting site are two factors that often receive minimal attention, but can have a significant impact on the quality of apple (Malus ×domestica) produced. A regional project, NE-183 The Multidisciplinary Evaluation of New Apple Cultivars, was initiated in 1995 to systematically evaluate 20 newer apple cultivars on Malling.9 (M.9) rootstock across 19 sites in North America. This paper describes the effect of cultivar and site on fruit quality and sensory attributes at a number of the planting sites for the 1998 through 2000 growing seasons. Fruit quality attributes measured included fruit weight, length: diameter ratio, soluble solids concentration (SSC), titratable acidity (TA), flesh firmness, red overcolor, and russet. Fruit sensory characteristics rated included crispness, sweetness, and juiciness, based on a unipolar intensity scale (where 1 = least and 5 = most), and acidity, flavor, attractiveness, and desirability based on a bipolar hedonic scale (where 1 = dislike and 5 = like extremely). All fruit quality and sensory variables measured were affected by cultivar. The two-way interaction of cultivar and planting site was significant for all response variables except SSC, TA, russet, crispness, and sweetness ratings. The SSC: TA ratio was strongly correlated with sweetness and acidity sensory rating, but was weakly correlated with flavor rating. The results demonstrate that no one cultivar is ideally suited for all planting sites and no planting site is ideal for maximizing the quality of all apple cultivars.

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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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Kelly T. Morgan, T.A. Obreza, and J.M.S. Scholberg

Understanding the growth pattern of fibrous, orange tree [Citrus sinensis (L.) Osbeck] roots enables proper fertilizer placement to improve nutrient uptake efficiency and to reduce nutrient leaching below the root zone. The objective of this study was to develop relationships defining citrus fibrous root length density (FRLD) as a function of soil depth, distance from the tree trunk, and tree size. Root systems of 18 trees with tree canopy volumes (TCV) ranging from 2.4 to 34.3 m3 on two different rootstocks and growing in well-drained sandy soils were sampled in a systematic pattern extending 2 m away from the trunk and 0.9 m deep. Trees grown on Swingle citrumelo [Citrus paradisi Macf. × Poncirus trjfoliata (L.) Raf.] rootstock had significantly greater FRLD in the top 0.15 m than trees on Carrizo citrange (C. sinensis × P. trifoliata). Conversely, Carrizo citrange had greater FRLD from 0.15 to 0.75 m below the soil surface. FRLD was significantly greater for ‘Hamlin’ orange trees grown on Swingle citrumelo rootstock at distances less than 0.75 m from the tree trunk compared with those on Carrizo citrange. Fibrous roots of young citrus trees developed a dense root mat above soil depths of 0.3 m that expanded both radially and with depth with time as trees grow and TCV increased. Functional relationships developed in this study accounted for changes in FRLD with increase in tree size.