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- Author or Editor: Michele Warmund x
‘Emma K’, ‘Kwik Krop’, and ‘Sparrow’ black walnuts (Juglans nigra L.) were collected weekly in Sept. and Oct. 2007 to determine the effect of delayed hulling of fruits on kernel color at successive harvest dates. Delayed hulling of fruits resulted in lower kernel color values, including L*, chroma, hue angle, and LCH sum (L* + chroma + hue angle values) than those of fruits that were immediately hulled after harvest. ‘Sparrow’ kernels were visually the darkest brown color after delayed hulling. However, the effect of delayed hulling (i.e., change in kernel LCH sum values) over all harvest dates was greatest for ‘Emma K’. LCH sums of kernels generally decreased as the time of harvest was delayed. For ‘Sparrow’, mean kernel LCH sums from immediately hulled fruits decreased sharply from the third week of harvest on 20 Sept. (i.e., the “normal” date of harvest) to the next week. This decrease in LCH sums represented a change in kernel color classification from medium brown at Week 3 to dark brown in Week 4. Visual color changes for ‘Kwik Krop’ were less apparent as a result of the narrow range of color over harvest dates.
`Earliglow' strawberry (Fragaria × ananassa Duch.) plants were frozen to -5C to examine the distribution of ice in the crowns. Anatomical studies were also performed to characterize tissue growth in a greenhouse at 4, 8, and 16 weeks after freezing to -5C. Ice masses observed in fresh crown tissue corresponded to the presence of extracellular tissue voids in specimens fixed for scanning electron microscopy (SEM). Voids were present near the peduncle and adjacent to the vascular system in crown tissue. After plants were grown in the greenhouse, cell division and enlargement were observed near the voids in crowns subjected to -5C. By 15 weeks after freezing, a few small extracellular voids remained in the crowns.
`Earliglow' strawberry (Fragaria xananassa Duchesne) plants were frozen to -5 or -50C to examine the distribution of ice in the crowns. Anatomical studies were also performed to characterize tissue growth in a greenhouse at 4, 8, and 15 weeks after freezing to -5C. Ice masses observed in fresh crown tissue corresponded to the presence of extracellular tissue voids in specimens fixed for scanning electron microscopy (SEM). Voids were present near the peduncle and adjacent to the vascular system in crown tissue. After plants were grown in the greenhouse, cell division and enlargement were observed near the voids in crowns subjected to -5C. By 15 weeks after freezing, a few small extracellular voids remained in the crowns. Tissue voids were also present in crowns of plants frozen rapidly to -50C and subsequently thawed. Cells in the crown of these plants were intact and did not appear collapsed after exposure to -50C, a lethal temperature.
The effect of crown diameter on the regrowth of `Earliglow' and `Honeoye' strawberry (Fragaria × ananassa Duch.) plants was evaluated following exposure to sub-freezing temperatures. Large-diameter (12-14 mm) crowns of both cultivars had greater leaf number and dry weight than medium (9-11 mm) and small (6-8 mm) diameter crowns when plants were grown in the greenhouse after the freezing test. Large diameter crowns of both cultivars and medium-diameter crowns of `Honeoye' plants produced greater root dry weight than those of small-diameter crowns. The number of days to bloom of the primary flower increased with exposure to lower temperatures only in the large-diameter crowns of `Earliglow'. However, in small-diameter crowns of `Honeoye', the time of bloom decreased with exposure to lower temperatures. The fruit weight of small- and large-diameter crowns of `Earliglow' plants decreased linearly with exposure to lower temperatures. `Honeoye' plants subjected to -7C and unfrozen control plants had similar fruit weight.
Studies were conducted to characterize altered tissues of larvae-infested buds and stem and leaf galls induced by Dryocosmus kuriphilus Yasumatsu on Chinese chestnut trees (Castanea mollissima Blume) and to describe gall inhabitants. Bud and gall samples were collected from chestnut trees growing in Mantua, OH, on 2 Mar. and 3 May 2012, respectively, and prepared for microscopy. Uni- and multilocular larval chambers containing one D. kuriphilus larva per chamber were observed in buds and stem galls. Evidence of insect-modified Castanea cells was present as a two-layer zone of hypertrophied plant cells adjacent to the larval chambers before budbreak on 2 Mar. By 3 May, stem and leaf galls were in the growth and differentiation stage of development. Within galls, torn cell walls and disorganized organelles were visible in the protoplasm of cells surrounding ovoid-shaped larval chambers. A continuous layer of nutritive cells with large nuclei and nucleoli, abundant lipid bodies and mitochondria, and fragmented vacuoles was contiguous to larval chambers. At the outermost region of the nutritive tissue, cells had recently divided. Larger vacuolated cells, with slightly thickened walls, were observed surrounding recently divided cells. Thin-walled parenchyma cells in the chestnut gall cortex had large vacuoles with fewer organelles than those of the nutritive layer. Vascular tissue within the gall was connected with that of the plant host tissue outside the gall. In some chestnut galls, a single parasitoid larva was found attached to a D. kuriphilus larva. Each parasitoid larva had six pairs of setae on its head capsule, a pair of clypeal setae, a notched labrum, a semicircular lobed labium, 13 post-cephalic body segments, and rows of long, erect setae on all body segments.
Chinese chestnut (Castanea mollissima Blume) is an exotic species that has potential as a niche crop. As a nut crop, it is relatively precocious in its bearing habit and has resistance to chestnut blight, tolerance to low winter temperatures, and relatively few pests. Current prices for fresh chestnuts are as much as $14/kg. Most U.S. chestnut growers (64%) have small orchards (less than 4 ha) and have been producing this crop for less than 10 years. Commercial chestnut production is low (≈680,000 kg) in the United States, but it is a relatively new industry in the central region. Limitations to growing this crop include a shortage of grafted trees, high tree costs, low yield efficiency, and high labor costs resulting from limited large-scale harvest equipment in the United States. However, results of ongoing research using cultivars on dwarfing rootstocks, thinning of secondary (2°) flowers, and improved tree nutrition will likely enhance profitability of production. In a 2003 Missouri survey, 67% of those interviewed had never consumed Chinese chestnuts but associated chestnut roasting with holidays. Chinese chestnuts provide health benefits. including a source of dietary fiber, a significant amount of vitamin C, no cholesterol, and are gluten-free.
Experiments were conducted to determine the temperatures at which different densities of INA bacteria incite ice crystallization on `Totem' strawberry flowers and to determine if there is a relationship between densities of INA bacteria on strawberry flowers and floral injury. Primary flowers were inoculated with Pseudomonas syringae at 106 cells/ml buffer, incubated at 25°C day/10°C night and 100% RH for 48 h, and exposed to –2.0°C. No ice nucleation occurred on these inoculated flowers and all of the flowers survived. However, when inoculated flowers were subjected to lower temperatures, ice nucleation occurred at –2.2°C and few of the flowers survived. In contrast, ice crystals formed on the surface of most non-inoculated flowers at –2.8°C and 21% of the flowers survived exposure to –3.5°C. When INA bacterial densities were ≈105 colony forming units/g dry wt, floral injury occurred at a warmer temperature than to flowers that had lower bacterial densities.
The time of rest completion of `Apache', `Arapaho', `Chickasaw', `Darrow', `Kiowa', `Navaho', and `Shawnee' blackberry (Rubus subgenus Rubus Watson) buds was compared and various models for estimating chilling were evaluated. `Kiowa' and `Arapaho' buds had the shortest rest periods, while those for `Shawnee', `Navaho', and `Chickasaw' buds were intermediate. `Apache' and `Darrow' buds had the longest rest periods. The model that accounted for the variation in percent budbreak among cultivars and temperatures during two dormant periods had the following two components: 1) a chilling inception temperature of –2.2 °C and 2) weighted chilling hours that accumulated after the chilling inception temperature. The chilling hours in this model were weighted as follows: 0 to 9.1 °C = 1; 9.2 to 12.4 °C = 0.5; 12.5 to 15.9 °C = 0; 16 to 18 °C = –0.5; >18 °C = –1. This study also elucidated that a blackberry model with a chilling inception temperature of –2.2 °C estimated chilling more accurately than one with chilling inception just after the maximum negative accumulation of chill units as used in the Utah chilling model. Also, temperatures between 0 and 2.4 °C must be weighted more heavily in a blackberry model than in the Utah peach model to accurately estimate chilling and rest completion.
Inflorescences of `Earliglow' and `Honeoye' strawberry (Fragaria ×ananassa Duch.) plants were subjected to controlled freezing tests to determine the cold tolerance of styles, anthers, and receptacles of individual flowers at various stages of development. Flowers of both cultivars tended to deacclimate as the stages of development progressed. Styles and receptacles generally exhibited injury at higher temperatures than anthers. The greatest deacclimation of styles and receptacles of primary flowers occurred at earlier developmental stages of `Honeoye' than of `Earliglow'. However, at the sixth stage of development, the critical temperature for receptacle injury in primary and secondary fruit was -3C for both cultivars.
Differential thermal analyses (DTA) and freeze viability tests were conducted to investigate the biophysics of freezing in floral buds of `Danka' black (Ribes nigrutn L.) and `Red Lake' red currants [Ribe.s sativum (Rchb.) Syrne] sampled from Nov. 1989 through Mar. 1990. Scanning electron microscopy was also used to determine the relationship between floral morphology and the freezing characteristics of the buds. Floral buds had multiple abrupt low-temperature exotherms (LTEs) and one or two broad LTEs in DTA tests. Abrupt LTEs from DTA were associated with apparent injury to the inflorescence in viability tests. The number of LTEs did not correspond to the number of racemes or flowers per bud, indicating that several flowers froze simultaneously. DTA experiments conducted in Dec. 1990 revealed that the broad exotherm detected between - 14 and - 20C in `Danka' samples resulted from freezing of supercooled water in the outer nonliving region of the periderm of cane tissue attached to the bud.