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Donald N. Maynard and Donald L. Hopkins

Watermelon (Citrullus lanatus [Thunb.] Matsum & Nakai) fruit are affected by a number of preharvest disorders that may limit their marketability and thereby restrict economic returns to growers. Pathogenic diseases discussed include bacterial rind necrosis (Erwinia sp.), bacterial fruit blotch [Acidovorax avenae subsp. citrulli (Schaad et al.) Willems et al.], anthracnose [Colletotrichum orbiculare (Berk & Mont.) Arx. syn. C. legenarium (Pass.) Ellis & Halst], gummy stem blight/black rot [Didymella bryoniae (Auersw.) Rehm], and phytophthora fruit rot (Phytophthora capsici Leonian). One insect-mediated disorder, rindworm damage is discussed. Physiological disorders considered are blossom-end rot, bottleneck, and sunburn. Additionally, cross stitch, greasy spot, and target cluster, disorders of unknown origin are discussed. Each defect is shown in color for easy identification.

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Nenita V. Desamero and Billy B. Rhodes

Vitrification, a physiological disorder characteristic of in vitro grown plants, was observed in single-node cultures of sweet potato in mannitol-enriched medium during their second year of storage. Vitrified or vitreous sweet potato plantlets were watersoaked, translucent or glassy in appearance, with thick, swollen, leaves and stems, stunted shoot growth and poor root growth. These plantlets were not able to regenerate normal plants when transferred into fresh regeneration medium nor were they able to survive outside culture conditions.

Electron microscopy revealed changes in the ultrastructures of vitrified sweet potato plantlets. Vitrified plants had defective stomatal complex, starch grain-filled chloroplasts, disrupted cell wall, big air spaces (lacunae), high frequency of cell membrane separation from the cell wall, nuclear disintegration, and cytoplasmic disorganization. These changes in the internal structures of vitrified plants were reflected in their abnormal morphology and physiology.

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Luis Luchsinger, Alvaro Villalobos, and Antonio Lizana

Postharvest response to high CO2 controlled atmosphere (CA) was studied in the blueberry (Vaccinium corymbosum L.) cultivar Elliot. Fruit was stored at 0 °C, 90% relative humidity and 15%, 18%, and 21% of CO2 and 5% of O2 and in air (0.03% CO2 and 21% O2). Evaluations were performed after 30 and 60 days of storage and an aditional period of 3 and 6 days at 10 °C (ripening period). Parameters meassured were: color (lightness, hue, and chroma), firmness, soluble solids (SS), titrable acidity (TA), SS/TA ratio, pH, weight loss, decay, physiological disorders, and appearance. The CA caused a positive effect, preserving the quality of the fruit in storage, by decreasing the respiratory rate and decay incidence. The 15% CO2 controlled atmosphere presented the best firmness and lowest decay. Acceptable conditions of quality were kept for 60 days of storage.

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Francisco Artés, Angel J. Escriche, and Jose G. Marin

Several intermittent 13C warming treatments were applied to `Primofiori' lemons (Citrus limon Burn) stored at 2 or SC. Fruit stored at 13C were treated with 10%, 2090, or 30% CO2 for 24 hours at weekly intervals. Reduction in decay and physiological disorders was best with two cycles of 2 weeks at 2C and 2 weeks at 13C and relative humidity >95 %. Under this storage condition, soluble solids concentration, pH, titratable acidity, and reducing sugars did not change relative to values at harvest, but the concentration of ascorbic acid increased and that of nonreducing sugars decreased in relation to harvest values. Carbon dioxide treatments did not prevent the development of alternaria (Alternaria citri Ell. & Pierce) rot and red blotch disorder, but effectively prevented the development of membranosis, rind pitting, and oleocellosis.

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Nenita V. Desamero and Billy B. Rhodes

Vitrification, a physiological disorder characteristic of in vitro grown plants, was observed in single-node cultures of sweet potato in mannitol-enriched medium during their second year of storage. Vitrified or vitreous sweet potato plantlets were watersoaked, translucent or glassy in appearance, with thick, swollen, leaves and stems, stunted shoot growth and poor root growth. These plantlets were not able to regenerate normal plants when transferred into fresh regeneration medium nor were they able to survive outside culture conditions.

Electron microscopy revealed changes in the ultrastructures of vitrified sweet potato plantlets. Vitrified plants had defective stomatal complex, starch grain-filled chloroplasts, disrupted cell wall, big air spaces (lacunae), high frequency of cell membrane separation from the cell wall, nuclear disintegration, and cytoplasmic disorganization. These changes in the internal structures of vitrified plants were reflected in their abnormal morphology and physiology.

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Robert E. Paull and Chris B. Watkins

Production of heat shock proteins (HSP) in response to high temperatures are a highly recognizable feature of plant and animal systems. It is thought that such proteins play a critical role in survival under supraoptimal temperature conditions. The use of heat treatments has been examined extensively, especially for disinfestation of fruit and disease control. Heat treatments can affect physiological responses, such as ethylene production, softening, and other ripening factors, as well as reducing physiological disorders, including chilling injury. HSPs have been implicated in a number of stress responses, but the extent that they are involved, especially in amelioration of chilling injury, is a subject of debate. In a number of cases, heat shock proteins do not appear to be involved, and HSPs do not explain long-term adaptation to heat; other systems for which we do not have models may be at work. Resolution of these issues may require the use of transgenic plants with modified heat shock responses.

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Paulo Roberto Ernani, Jaques Dias, Cassandro Vidal Amarante, and Diorvania Ribieiro

Calcium sprays have improved quality and storage life of apples throughout the world as a result of Ca prevention of many fruit physiological disorders. The efficacy of Ca sprays, however, varies according to soil, cultivar/rootstock, orchard cultural practices, and weather conditions. This study was carried out from 1998 to 2004 in southern Brazil in order to assess the effect of Ca sprays on quality of `Gala' fruits in an orchard planted in 1988 on a density of 1234 trees/ha. Treatments consisted of 0, 4, 8, and 12 sprays of 0.5% CaCl2. Fruits of same size and maturity level were annually analyzed at harvest and after 5 months of cold storage. In five out of six seasons, fruits from all treatments were free of any physiological disorder, and Ca sprays had no effect on leaf composition and on fruit quality attributes (soluble solids, acidity, starch pattern index, flesh firmness, and concentrations of N, K, Ca, and Mg). In the 2000–01 season, however, when yield was 18 t·ha-1 and fruits had an average weight of 175 g, the incidence of bitter pit plus lenticel blotch pit on stored fruits decreased from 24% in the treatment with no calcium to 2% in that with 12 calcium sprays. Two seasons later, yield was also light (25 t·ha-1) and fruits were big in size (168 g), but they did not show any disorders regardless of Ca sprays. It seems that the incidence of Ca related disorders in `Gala' apples grown on limed soils in Brazil only occurs in seasons with a light crop load as a result of large fruits and a high leaf/fruit ratio, associated with some unknown climatic factor.

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Mathieu Ngouajio, William Kirk, and Ronald Goldy

Nondestructive estimates of fruit volume are used for yield prediction. They are also used to study the relationship between fruit expansion rate and susceptibility to diseases or physiological disorders such as fruit cracking. A model relating bell pepper (Capsicum annuum) fruit diameter and length to its volume was derived using the equation of the volume of a sphere as the starting point. The model has the following formula: VF = KD2 Lπ/6, where VF is fruit volume, K is the shape factor that varies with fruit type, D is fruit diameter, and L is fruit length. The model is simple, easy to use in the field, and may account for variations in fruit shape. Regression analyses using actual fruit volume of bell pepper measured with the water displacement method and the volume estimated using different equations showed that accuracy of the new model is comparable to that of one of the best models previously proposed. However, because the model is less complex than previous models, it is easier to use in the field.

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Anusuya Rangarajan and Theodore W. Tibbitts

Oedema, a physiological disorder, affects several cultivars of ivy geranium [Pelargonium peltatum (L.) L `Hér. ex Ait) when grown in greenhouses. This study investigated the regulation of oedema on this crop using far-red radiation because these wavelengths inhibited the injury on Solanaceous sp. Plants were exposed to far-red radiation from Sylvania #232 far-red lamps on abaxial and adaxial surfaces of leaves. A far-red photon flux of 15 to 20 μmol·m-2·s-1 (700-S00 nm) was not effective in preventing oedema injury. A far-red abaxial treatment during the light period tended to reduce the amount of injury that developed when photosynthetic photon flux was low (130-170 μmol·m-2·s-1), but this inhibition of the injury was absent with higher photon flux. The results from these studies indicate the use of supplemental far-red radiation treatments in greenhouses would not be justified because adequate and consistent control of the injury on ivy geraniums was not achieved.

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Wol-Soo Kim, Tae-Hyun Kim, Soon-Ju Chung, and Hyun Suk Choi

Germanium has been reported as a mineral element affecting plant cell metabolism. Many trials to supply germanium to fruit have been carried out since tests have confirmed germanium's role as a medical substance. Supplying germanium to orchards by soil and foliar application was not effective because of loss from rainfall. Also, tree injection with germanium solution required the insertion of a tube to the tree xylem at each injection site. In order to increase germanium absorption by fruit, this study carried out the postharvest dipping of fruit into germanium solution. `Niitaka' pear (Pyruspyrifolia) fruit was treated with two types of germanium, GeO (inorganic type) and Ge-132 (organic type), in a concentration of 50 mg·L–1 just after harvest in early Oct. 2004. Flesh browning after peeling the fruit was delayed by germanium treatment, and polyphenoloxidase (PPO) activities were lowered. Postharvest potentials were maintained at high levels for fruit firmness, physiological disorders, and decayed fruit during cold storage at 0 to 1 °C for 2 months. Antioxidant and some phenolic compounds were higher than those of control fruit.