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Krista C. Shellie

A collection of 23 red and six white wine grape (Vitis vinifera) cultivars were evaluated for viticultural performance in Parma, ID. Vine yield, fruit composition, and vegetative growth were measured over four growing seasons, and data were used to compare relative cultivar performance based on yield to pruning ratio and fruit maturity. Relative differences among cultivars in budbreak day of year [96 (6 Apr.) to 122 (2 May)] and days from budbreak to harvest (143 to 179 days) varied from year to year. The earliest and latest maturing cultivars in 3 of 4 years were ‘Blauer Portugieser’ (143 days), ‘Nebbiolo’ (177 days), ‘Barbera’ (179 days), ‘Orange Muscat’ (144 days), ‘Flora’ (149 days), ‘Muscat of Alexandria’ (166 days), and ‘Viognier’ (168 days). Cultivars differed in yield (2.4 to 7.0 tons/acre), vegetative vigor (4.6 to 20.4 yield/pruning weight), and harvest soluble solids concentration (21.1 to 26.5), but differences in harvest pH (3.0 to 4.1) and titratable acidity (2.48 to 13.03 g·L−1) varied from year to year. Average heat unit accumulation (1646) was 160 units higher than the 78-year site average. Few (less than 150) units accumulated in April and October, most units accumulated in July, and diurnal difference in air temperature was ≈15 °C. Performance results from this study can assist cultivar site selection by comparing climate data for an intended site with that of Parma. For example, the low acidity and earliness of ‘Blauer Portugieser’ suggests it is best suited to a site with less heat unit accumulation than Parma, and the high acidity and late maturity of ‘Barbera’, ‘Nebbiolo’, and ‘Carignan’ suggest these cultivars are best suited to a site with more heat unit accumulation than Parma. The inconsistent relationship between onset of budbreak and earliness observed in this study suggests opportunity to match short-season cultivars late to break bud such as Flora to short-season growing sites prone to late-season frost.

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Krista C. Shellie

`Manila' mangoes (Mangifera indica) were immersed in 46C water for 65 or 75 minutes, or exposed to 45, 50 or 52C moist, forced-air (MFA) for 240, 100, and 98 minutes, respectively Mangoes exposed to 50 or 52C MFA had a significantly higher incidence of internal cavitation than mangoes exposed to 45C MFA; mangoes immersed in 46C water for 65 or 75 minutes, or control fruit. Shrink wrapped and nonshrink wrapped mangoes were exposed to 45C MFA for 240 minutes or 52C MFA for 98 minutes to evaluate whether the concentration of oxygen and carbon dioxide inside the fruit influenced cavitation development. Shrink wrapping per se had no significant effect on cavitation development Mangoes heated in 45C MFA for 240 minutes, 52C MFA for 98 minutes, or 46C water for 65 minutes were hydrocooled in 23C water or air cooled at 23C to evaluate whether heat dose influenced cavitation development. Hydrocooling had no significant effect per se on cavitation development though it significantly reduced the heat dose. The above results suggest that tolerance of 'Manila' mango to disinfestation heat treatments is more influenced by a maximum flesh temperature threshold than the heating method, heat dose, or fruit internal atmosphere.

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Krista C. Shellie

Export and domestic marketing of grapefruit (Citrus paradisi Macf.) can be limited by phytosanitary barriers against fruit fly species and growth of decay organisms, especially green mold (Penicillium digitatum Sacc.), during the marketing process. The objective of this research was to identify whether the dose of high-temperature forced air that providing quarantine security against Mexican fruit fly could also beneficially control the growth of green mold during subsequent storage. `Rio Red' grapefruit were harvested four times in 1995 and nine times in 1996 and challenge-inoculated with 10 L of a 1 × 106 spores/ml spore solution (10,000 spores) of green mold before or after exposure to 46°C forced air for 300 min. Control fruit were challenge-inoculated but not exposed to the heat treatment. The growth of green mold was quantified by measuring lesion diameter after 3 days of storage at 23°C, 80% RH. Grapefruit inoculated prior to the heat treatment developed significantly smaller lesions than fruit inoculated after the heat treatment or fruit not exposed to a heat treatment. The average lesion diameter of fruit inoculated prior to the heat treatment was 2.5 and 0.9 cm, respectively, in 1995 and 1996. The average lesion diameter of fruit inoculated after the heat treatment was similar to non heat-treated, control fruit. Lesion diameter of control and post heat-challenged fruit were 6.4 and 6.1 cm in 1995 and 5.7 and 5.3 cm in 1996. Results suggest reduction in decay be attributed to alteration in the pathogenicity of green mold after exposure to the heat treatment rather than an altered resistance of the fruit to the pathogen.

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Krista C. Shellie

Green mold, a predominant disease of citrus fruit, develops when spores of Penicillium digitatum infect extant wounds in fruit epidermal tissue. Development of green mold during shipping limits the distance grapefruit can be surface transported. The objective of this research was to evaluate whether altering the atmosphere during refrigerated storage could suppress development of green mold. In the first two experiments, growth of green mold was evaluated after fruit were stored in ultra-low oxygen (0.05 or 1 kPa) at 14, 16, or 18 °C for up to 21 days. In the last two experiments, grapefruit were stored for 14 or 21 d at 12, 13, or 14 °C in atmospheres containing 2, 5, or 10 kPa oxygen with or without 2, 5, 10, or 20 kPa carbon dioxide. In all experiments, grapefruit were inoculated with 10 or 20 μL of a spore suspension of P. digitatum. Decay progression after storage was monitored by measuring the diameter of the lesion in cm at the demarcated site of inoculation or by subjectively rating percent decayed fruit surface area. Grapefruit not inoculated with P. digitatum had no visible symptoms of green mold. Grapefruit stored under controlled atmosphere had less fruit surface covered with mycelium (5% to 64%) than grapefruit stored in air. Inoculated grapefruit stored in 0.05 kPa oxygen for up to 14 d at 14 or 18 °C had no visible symptoms of green mold upon removal from cold storage, but developed a characteristic green mold lesion after 5 additional days of storage in air at ambient temperature. Results suggest that refrigerated controlled-atmosphere storage combined with wax and a fungicide can enhance control of green mold during shipping.

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Krista C. Shellie

An instrumented sphere (IS) was used to identify high-impact areas on seven grapefruit (Citrus paradisi Macf.) packing lines in the Rio Grande Valley of Texas. The packing-line unit operations having the greatest percentage of high impacts were 1) the sizer, 2) when #2 fruit were separated by hand at the grading table, 3) when fruit were dumped from the harvest bin onto the packing line, and 4) when fruit dropped into a collection bin at the end of the packing line. The number of high impacts and the amount of cushioning in high-impact areas varied among the seven packing sheds. The amount of red dye visible on the surface of fruit collected from the end of each shed's packing line did not correspond with each shed's percentage of high impacts or with incidence of decay during fruit storage. The severity of impacts and degree of cushioning provided in these Texas packing sheds were comparable to that reported for 39 Florida packing houses. This study illustrates the usefulness of the IS for enhancing individual packing-line operations and for comparing individual shed performance to packing-line operations in other agricultural production regions.

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Krista C. Shellie and David Wolf

“Netted” (Cucumis melo var. reticulatus Naud.) cantaloupes typically abscise when mature, and have a shorter postharvest life than “Honeydew” (Cucumis melo var. inodoris Naud.) -type melons. The amount of ethylene and carbon dioxide produced by two cantaloupe genotypes (slipping), one Honeydew genotype (non-slipping), and the F1 hybrids derived from the slipping x non-slipping genotypes were measured during ripening to understand the genetic control of ethylene and fruit abscission. Sterile, nondestructive gas sampling ports inserted into 20-day-old fruit were used to extract samples from the central cavity of the melons and monitor ethylene and carbon dioxide from day 30 until the fruit was horticulturally mature. Honeydew melons had a lower rate of respiration during maturation and ripening than Netted melons, and Netted melons produced 10-fold more ethylene during ripening than Honeydew types. F1 fruit produced ethylene at levels similar to the Netted parent, abscissed 2 to 4 days later than the Netted parent, yet respired during maturation and ripening like the Honeydew-type parent. Ethylene production, respiration, and abscission appear to be controlled by dominant gene action.

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Gene Lester and Krista C. Shellie

Physicochemical and sensory attributes of fully mature honey dew melon (Cucumis melo L. var. inodorus Naud.) fruits were evaluated 10 days after storage for eight commercial cultivars grown in two locations. Cultivars varied in degree of pref- erence expressed by panelists' ratings for overall fruit preference, flavor, and shape and for physicochemical measurements of soluble solids concentration (SSC), flesh firmness, and fruit weight. The sensory attribute that correlated most strongly with overall fruit preference was fruit flavor (r = 0.97). The whiteness of epidermal tissue (rind L value) and SSC correlated more highly with overall fruit preference (r = 0.54 and r = 0.52, respectively) than other physicochemical attributes, such as fruit firm- ness (r = -0.24) and fruit weight (r = -0.12). Epidermal L value correlated more strongly with panelists' ratings for fruit shape (r = 0.69) than with fruit flavor (r = 0.35), but SSC correlated more strongly with fruit flavor (r = 0.61) than with fruit shape (r = 0.30). Superior honey dew melon quality at harvest was associated with high SSC, white epidermal tissue, and round fruit shape.

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Krista C. Shellie and Ken Rodde

A treatment schedule for disinfesting grapefruit of Mexican fruit fly with refrigerated (14 °C) storage for 21 days in ultra-low oxygen (0.05 kPa) was tested using a fully loaded, 24-ft sea freight container. The objective of this research was 3-fold: 1) evaluate the ability of a free standing Electronic Oxygen Control system to maintain 500 ppm of oxygen for 21 days inside the sealed container, 2) evaluate the mortality of third instar Mexican fruit fly larvae stored for 21 days inside the sealed container, and 3) evaluate fruit market quality after 21 days inside the container. The container was loaded with 17 pallets of red-fleshed, `Rio Star' grapefruit. Three boxes from each pallet were evaluated for fruit quality (decay (%), visible disorders (%)) after 21 days of treatment and again after 14 additional days of storage in air at 10 °C. Four cartons, each containing 24 fruit infested with third instar, Mexican fruit fly larvae, were each placed on top of a pallet in four different container locations. Upon completion of treatment, larvae were evaluated for survival. In the first replication, no fruit fly larvae survived the low oxygen treatment. In the second replication, oxygen concentration was less controlled, and 60 pupae survived the treatment. Treated and control grapefruit had similar incidence of decay when the treatment was terminated, however no sporulation was observed in fruit stored under ultra-low oxygen. Grapefruit exposed to ultra-low oxygen had a higher incidence of visible disorders, consisting of darkened, sunken areas on the fruit surface. It is unclear whether this damage is attributed to fluctuating levels of oxygen, deleterious volatiles produced during treatment, or a sensitivity of the fruit to low oxygen.

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Krista C. Shellie and Robert L. Mangan

`Valencia' oranges [Citrus sinensis (L.) Osbeck] were exposed to moist, forced air (MFA) at 46, 47, or 50C for 1, 2, 3, or 4 hours to identify the maximum temperature and duration of exposure for which there was no detectable reduction in fruit quality. The flavor of oranges exposed to MFA at 47 or 50C was rated significantly inferior to that of oranges exposed to 46C. The degree minutes that accumulated in the center of the fruit between 2 and 4 hours and the maximum fruit center temperature during the heat treatment were associated with inferior fruit flavor. Oranges exposed to MFA at 46C for up to 4 hours could not be distinguished from the nonheated fruit. MFA at 46C is a promising quarantine treatment for `Valencia' oranges.

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Krista C. Shellie and Mikal E. Saltveit Jr.

The CO2 and C2H4 conc in the internal cavity of three melon (Cucumis melo L., var. reticulatus and inodorus Naud.) cultivars was periodically measured in fruit attached to the vine and in fruit harvested 30 days after pollination (DAP). Gas samples were withdrawn through sterile serum stopper sampling ports aseptically installed near the equator of each fruit at ca. 20 DAP. Sampling continued until either 60 DAP or until fruit abscised. Internal CO2 and C2H4 conc increased in harvested fruit as they ripened (i.e., increased percent soluble solids, decreased flesh firmness, characteristic external color change). Fruit allowed to ripen on the vine also exhibited a rise in C2H4, but lacked a ripening associated climacteric rise in respiration, CO2 conc in attached fruit remained constant or declined as the C2H4, conc increased around 40-fold and the fruit ripened. The increase in CO2 conc, so commonly observed in ripening climacteric fruit, was observed in harvested melons, but not in fruit ripening on the vine. In melons, the respiratory climacteric may be an artifact of harvest. Implications of these observations will be discussed.