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Randolph Beaudry, Philip Schwallir, and Marian Lennington

Due to the the extremely high level of competition in the marketplace for stored apple fruit, the need for quality maintenance during storage is critical. Quality analysis of fruit at harvest supports the contention that there is a harvest period during which fruit picked for long-term controlled-atmosphere storage maximize grower returns. The apple maturity program used in Michigan for determining this optimal harvest period-or window -incorporates a bloom date-based prediction and fruit maturity analyses. Techniques used in collecting and disseminating maturity information and its interpretation are discussed.

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Wesley T. Watson*, David N. Appel, Michael A. Arnold, Charles M. Kenerley, and James L. Starr

Several techniques have been used to study root growth and pathogen movement along roots between trees, including profile walls, micro-rhizotrons, and soil cores. These assessments can be very time consuming, cost prohibitive, and ineffective when studying soilborne pathogen movement across overlapping roots between adjacent trees in an orchard. Three aboveground rhizotrons were designed and constructed to study the movement of Phymatotrichopsis omnivora (Duggar) Hennebert (syn. Phymatotrichum omnivorum Duggar) along overlapping apple roots [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf. (syn. M. domestica Borkh. non Poir.)] in simulated orchard conditions. Two experiments involved boxes using either observation windows or micro-rhizotron observation tubes between trees. A third experiment utilized 45-gallon containers (171,457 cm3) joined by innovative observation windows. The container rhizotrons reduced labor and material costs, were more effective at monitoring roots, were more convenient than field measurements, and more closely simulated orchard growing conditions. This method provides several advantages to better study and manipulate the rooting environment of orchard-grown trees.

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Kent D. Kobayashi and H.C. Bittenbender

In 1988, the Farmer's Bookshelf started out as a computerized information system of crops grown in Hawaii. The first version was created on an Apple Macintosh computer using a hypermedia program called HyperCard. Because HyperCard came with each Macintosh computer, only the crop files needed to be sent to clientele. As the demand for an IBM-compatible version of the Farmer's Bookshelf increased, the Windows version was created using a hypermedia program called Plus. In addition to the crop files, the runtime version of Plus was also distributed to clientele. Later, other files were added to the Farmer's Bookshelf, including files to diagnose problems of macadamia in the field, select ground covers, select landscape trees, recommend fertilization, calculate nut loss for macadamia growers, and calculate turfgrass irrigation. Cost of analysis spread-sheets for several crops were also added. Recently, the Farmer's Bookshelf was moved to the World Wide Web, which has the advantages of reaching a world-wide clientele, easier updating and modifications, and linking to sites of related information. We have added links to newspaper articles on agriculture in Hawaii, to related sites on a particular crop, to on-line agricultural magazines and newsletters, to agricultural software, to upcoming agricultural events, and to Y2K sites. Because of the benefits of the Web version, the diskette versions (Macintosh and Windows) are no longer supported. Putting the Farmer's Bookshelf on the Web has allowed us to better meet the needs of our clientele for up-to-date information.

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Thomas E. Marler and Haluk M. Discekici

The influence of partial root volume irrigation on water relations and expansion of roots and leaves of papaya plants was determined using split root containers. In one study, `Tainung #1' and Solo #8 seedling roots were trained into four compartments until well-established, then water was withheld from 0, 1, 2, or 3 quadrants. Mid-morning stomatal conductance and predawn relative leaf water content were not affected by the irrigation treatments. Similarly, relative root water content in the dry quadrants was not different from that in the watered quadrants. In a second study, `Red Lady' seedling roots were trained into four compartments which contained a 13 × 13-cm plexiglass observation window. After the plants were well-established, watering was continued in one of 4 (1:4) or four of four (4:4) quadrants. Leaf midrib and root extension were measured at 06:00 and 18:00 hr each day. Daily growth of roots in the dry quadrants was reduced 25% below that in the watered quadrants, and midrib extension of the 1:4 plants was reduced ≈10% below that of the 4:4 plants. Irrigation treatments did not influence the percentage of growth occurring during the diurnal and nocturnal periods. The dry quadrants of 1:4 plants were almost devoid of fine roots. The number of root tips on the observation windows of the 1:4 plants was reduced 43% in the dry quadrants and increased 22% in the wet quadrant compared with that for the 4:4 plants.

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James W. Rushing

Mature-green tomatoes stored up to 8 weeks at 11.5°C under 4% oxygen with no accumulation of carbon dioxide above ambient had reached turning stage of color by the end of the storage period. Control tomatoes stored at identical temperature without CA quickly turned red and were unmarketable after 4 weeks due to overripenessand high incidence of decay. Tomatoes held under CA for 8 weeks and then transferred to 20°C without CA ripened normally to full-red color within 10 days with less than 10% decay and no apparent mealiness or other symptoms of chilling injury. Weight loss from tomatoes stored under CA increased with storage time, but, after 8 weeks, the fruit still did not have noticeable shrivelling and visual appearance was excellent compared to tomatoes purchased from a local supermarket. Results of this research suggest that short-term CA storage is a feasible method of expanding the market window for tomatoes. This could be particularly useful for production regions such as South Carolina, where the harvest is practically completed within a 3-week window and low prices often prevail during the harvest period.

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R.J. Campbell and C. de B. Campbell

Mango (Mangifera indica L.) currently ranks fifth, along with apple, among fresh fruit imported by the United States, with more than 142,000 MT imported in 1995. Imports have doubled in the past 5 years and are projected to increase by 20% to 30% by the year 2000. Mexico supplied >80% of the imported volume in 1995, with the remaining 20% supplied by Brazil, Ecuador, Guatemala, Haiti, Nicaragua, Peru, and Venezuela. Individual production areas (countries) have traditionally controlled a market, defined by time of year, resulting in a near 12-month supply of mangos in the United States in the past few years. However, market share among producing countries is rapidly changing as individual producers and production regions extend their season through the use of different available microclimates, bloom manipulation, and new cultivars. With this extension of production season in each region, there is now significant market overlap and traditional regional windows have been shortened or eliminated. Producers in all regions must now make timely management decisions to assure their future profitability. A holistic management scheme involving attention to fruit quality, cultivar selection, volume consistency, and marketing is presented. Such a management plan is key to an individual region's success in establishing and holding a given market window.

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J. Roger Harris, Richard Smith, and Jody Fanelli

Rapid posttransplant root growth is often a determining component of successful establishment. This study tested the effect of transplant timing on first-season root growth dynamics of bare-root Turkish hazelnut trees. Trees were either harvested and planted in the fall (F-F), harvested in the fall and planted in the spring after holding in refrigerated storage (F-S), or harvested and planted in the spring (S-S). All trees were transplanted into 51-L containers, adapted with root observation windows. Root growth began in F-F and F-S trees 1-2 weeks before spring budbreak, but was delayed in S-S trees until ≈3 weeks after budbreak. Budbreak was 6 days earlier for fall-harvested than for spring-harvested trees. No new roots were observed before spring. Root length accumulation against observation windows (RL) was delayed for S-S trees, but rate of increase was similar to F-F and F-S trees soon after growth began. Seasonal height, trunk diameter growth, and RL were similar among treatments. Surface area of two-dimensional pictures of entire rootballs was not correlated with seasonal RL.

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Gwendolyn H. Pemberton and A.A. De Hertogh

Dutch-grown `Deutschland', `Fanal', and `Rheinland' Astilbe, harvested 1 Nov. 1992 and shipped to the United States, were dissected to determine the stage of floral development after 0, 2, 4, 6, 8, 10, 12, or 15 weeks of 2C storage. Astilbe crowns were also planted after 15 weeks of 2C storage and floral development was determined after 1, 2, or 3 weeks of greenhouse forcing. On arrival, multiflower inflorescences were clearly visible. A pattern of abortion and reinitiation occurred during 2C storage. Floral development was markedly repressed when ecodormancy was imposed, but development resumed during greenhouse forcing. During the observational period, floral organ numbers were variable, and morphological abnormalities were observed. In a second experiment, physiological maturity of the crowns was evaluated by harvesting crowns of `Bumalda', `Europa', `Federsee', and `Rheinland' on 15 Sept., 1 Oct., 15 Oct., 1 Nov., and 15 Nov. in The Netherlands. Optimal harvest period was from 1 Oct. to 1 Nov., depending on the cultivar. Crowns harvested before this period were physiologically immature. Crowns harvested during the 4-week window produced the highest overall plant quality and performed as physiologically mature crowns. Astilbe crowns harvested after the 4-week window produced plants with lower forcing qualities and were determined to be beyond the optimal physiological state for forcing.

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Jeffrey W. Burcaw, Bruce W. Wood, and Michael W. Pool

The authors have developed a mathematical model designed for shade-intolerant tree crops which describes the amount of intertree shading in an orchard. These data are used to formulate an optimal orchard design based on shading reduction in orchards for any tree crop during any developmental window at any global location for either continuous canopy hedgerows or non-intersecting canopies for several different orchard geometries. Variables include tree shape, orchard geometry intertree spacing, row orientation, time and day of year, and geographical coordinates. Optimal orchard designs are based upon the total amount of unshaded canopy surface per unit area which each orchard configuration confers. Results indicate extensive variability of intertree shading between hedgerow and non-intersecting canopies to be largely a function of latitude, regardless of other variables.

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Edward F. Gilman

Due to the high cost of color separations, few plant materials texts have photographs and line drawings showing each plant at different times of the year and at different ages. CD-ROM computer technology allows the user ready access to this information at a reasonable cost. Horticulturists at the University of Florida have developed three CD-ROM discs for use throughout the U.S. The discs contain more than 3000 pages of text, extensive morphological characteristics and plant use suggestions, in addition to more than 2000 line drawings and nearly 3600 photographs of more than 1,800 plant species. Software developed for DOS and Windows allows the student to generate customized plant lists for landscape sites. Lists can be created to match specific site characteristics, desirable ornamental attributes, or both. Students can also use the programs to help identify unknown plant specimens. Other features allow viewing of insect and disease problems and access to up-to-date control recommendations.