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Kentucky State Univ. (KYSU) emphasizes research on developing alternative, high-value crops and sustainable agriculture methods for use by limited-resource farmers. Since 1990, KYSU has maintained a research program to develop pawpaw into a new high-value tree fruit crop. With its high tolerance for many native pests and diseases, pawpaw shows great potential as a crop for organic and sustainable production. The objectives of KYSU's pawpaw research program include: 1) variety trials; 2) development of new or improved methods of propagation; 3) collection, evaluation, preservation, and dissemination of germplasm; and 4) sharing of information on pawpaw with scientists, commercial growers and marketers, and the general public. To aid in dissemination of information on pawpaw, a web site has been developed (http://www.pawpaw.kysu.edu) that includes information on current and past pawpaw research at KYSU and information on the PawPaw Foundation. On this site, there are a selected bibliography of publications on pawpaw and related species; pawpaw recipes and nutritional information; a guide to buying and growing pawpaws; photos of pawpaw trees, flowers and fruit; and links to other web sites with pawpaw information. In the future, the site will include results from the pawpaw regional variety trials and the database for the National Clonal Germplasm Repository for Asimina spp., located at KYSU. The pawpaw information web site will be an increasingly useful aid in the introduction of pawpaw as a new, potentially high-value, tree fruit crop.

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Hylocereus undatus (Haw.) and H. polyrhizus (Weber) are new fruit crops of the Cactaceae. In Israel, flowers of the two species, which are self-incompatible, are hand cross-pollinated. In order to ensure a current supply of compatible pollen and guarantee good yields, we have developed a procedure for long-term storage of pollen. Pollen for storage was collected in the evening or in the morning. Its moisture content ranged between 45% to 50% in the evening and between 18% to 22% in the morning. Pollen was first dehydrated in a vacuum desiccator until the moisture content was reduced to 5% to 10% and then stored at various temperatures (+4, –18, –70, –196 °C) for 3 or 9 months, after which it was used for cross-pollination. Percent fruit set and fruit fresh weight (FW) were affected by the temperature but not the duration of pollen storage; storage at +4 °C reduced fruit set, fruit FW, and seed number more than did storage at subfreezing temperatures. The FW of fruits produced by frozen pollen was similar to that produced by fresh pollen in commercial orchards. The rate of seed germination was high (≈90%) regardless of the temperature during pollen storage.

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Hylocereus undatus (Haw.) and H. polyrhizus (Weber) are new fruit crops of the Cactaceae. In Israel, flowers of the two species, which are self-incompatible, are hand cross-pollinated. In order to ensure a current supply of compatible pollen and guarantee good yields, we have developed a procedure for long-term storage of pollen. Pollen for storage was collected in the evening or in the morning. Its moisture content ranged between 45% to 50% in the evening and between 18% to 22% in the morning. Pollen was first dehydrated in a vacuum desiccator until the moisture content was reduced to 5% to 10% and then stored at various temperatures (+4, -18, -70, -196 °C) for 3 or 9 months, after which it was used for cross-pollination. Percent fruit set and fruit fresh weight (FW) were affected by the temperature but not the duration of pollen storage; storage at +4 °C reduced fruit set, fruit FW, and seed number more than did storage at subfreezing temperatures. The FW of fruits produced by frozen pollen was similar to that produced by fresh pollen in commercial orchards. The rate of seed germination was high (≈90%) regardless of the temperature during pollen storage.

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Abstract

Traditionally, the size control achieved in summer-pruned apple (Malus domestica Borkh.) trees has been attributed to the removal of shoot leaf area before it could replace the storage carbohydrate depleted during its initial growth. Therefore, tissues of young Top Red ‘Delicious’/M 9 trees grown in pots, and mature, field-grown ‘Jonathan’/M 26 trees were summer-pruned and subsequently analyzed for carbohydrate and nutrient element content. Increasing the severity of summer pruning (the length of shoot removed) did not affect the concentration of water-soluble reducing sugars (SRS) or insoluble hydrolyzable carbohydrates (IHC) in the basal shoot section of the Top Red ‘Delicious’/M 9 trees 11 weeks after pruning. Summer pruning 1) increased leaf SRS, N, K, B and stem IHC and 2) decreased leaf Ca and Mg in shoot regrowth. Levels of Fe, Ca, Zn, Al, and Na in the leaves of regrowth were not affected by summer pruning. There was no significant effect of pruning on SRS or IHC levels in the roots. A separation of the carbohydrates by gas chromatography revealed increasing glucose and fructose concentrations in the roots as pruning severity increased, but sorbitol, sucrose, and phloridzin concentrations in roots were not significantly affected. Neither previous season’s summer pruning nor fruit cropping of ‘Jonathan’/M 26 trees affected SRS or IHC of spur shoots in March or June, except that presence of fruit reduced IHC of spur leaves in June. SRS levels in roots in June were reduced by the previous year’s cropping, but not influenced by summer pruning. Root IHC was not influenced by either pruning or cropping treatments. Spur leaf N, Ca, Mg, Mn, and Al were reduced on defruited trees, with K, Ca, Mn, and Al generally being increased by summer pruning. Pruning and cropping treatments generally did not affect levels of P, Fe, B, Cu, Zn, or Na in spur leaves in June; but summer pruning increased K concentration in harvested fruit.

Open Access

Zinc (Zn) deficiency is widespread throughout the world causing economic losses on a number of crops. Despite the fact that much information was generated during the last 20 years on Zn soil chemistry and its inorganic phase equilibrium, the mechanism controlling the amount of free Zn+2 present in the soil solution is not yet completely understood. This information is critical for the development of effective techniques of supplying Zn through the soil. As Zn moves very slowly through the soil, however, and a large portion of fruit tree root system occupies deep soil layers, foliar sprays with Zn are generally more effective than soil treatments in alleviating Zn deficiency symptoms. That is why many extension specialists recommend this approach. In view of the poor mobility of foliar-absorbed Zn in plants, however, we may need to reexamine this approach. Zinc foliar sprays may be effective in controlling Zn deficiency in leaves, but not in alleviating Zn deficiency in roots or subsequent flushes of growth. Also, the conditions under which fruit trees are most likely to respond to corrective Zn treatments are not well understood and the critical periods for Zn supply to assure optimal fruit set, fruit growth, and high fruit external and internal quality are not well defined. Field studies on fruit trees suggest that Zn deficiency must be quite severe to make the application of this element economically justifiable. In well-controlled greenhouse studies, however, growth responses were realized on plants only mildly affected by Zn deficiency. If considerable field variability may explain this discrepancy in the data, then future field research must use improved methodologies to properly quantify the impact of various levels of Zn deficiency on tree growth, fruit yield, and fruit quality.

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Mechanized harvest for processing markets has become commercially accepted for blackberries (Rubus sp.), highbush (Vaccinium corymbosum), lowbush (V. angustifolium) and rabbiteye (V. ashei), blueberries, cranberries (V. macrocarpon), grapes (Vitus labruscana, V. vinifera, V. rotundifolia, V. sp.), raspberries (Rubus ideaus) and to a lesser extent for strawberries (Fragaria × ananassa). Fruit bruising during harvest and sorting often contributes to reduced “eye appeal” and keeping quality for fresh sales. Highbush and rabbiteye blueberries are successfully machine harvested for fresh markets, however, high temperature and rain will often make product quality unacceptable. Highbush blueberries grown in cool climates and rabbiteye blueberries with greater inherent resistance to bruising have most consistently given acceptable quality. Cultivar improvement and equipment that causes less bruising during harvest and sorting will be required for increased mechanization for fresh markets. Mechanical pruning of blackberries, blueberries, grapes and raspberries can reduce costs by up to 80%. The audience will be involved in discussion of advancements in mechanization techniques.

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Mechanized harvest for processing markets has become commercially accepted for blackberries (Rubus sp.), highbush (Vaccinium corymbosum), lowbush (V. angustifolium) and rabbiteye (V. ashei), blueberries, cranberries (V. macrocarpon), grapes (Vitus labruscana, V. vinifera, V. rotundifolia, V. sp.), raspberries (Rubus ideaus) and to a lesser extent for strawberries (Fragaria × ananassa). Fruit bruising during harvest and sorting often contributes to reduced “eye appeal” and keeping quality for fresh sales. Highbush and rabbiteye blueberries are successfully machine harvested for fresh markets, however, high temperature and rain will often make product quality unacceptable. Highbush blueberries grown in cool climates and rabbiteye blueberries with greater inherent resistance to bruising have most consistently given acceptable quality. Cultivar improvement and equipment that causes less bruising during harvest and sorting will be required for increased mechanization for fresh markets. Mechanical pruning of blackberries, blueberries, grapes and raspberries can reduce costs by up to 80%. The audience will be involved in discussion of advancements in mechanization techniques.

Free access