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Michele R. Warmund

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.

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Michele R. Warmund

`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.

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Michele R. Warmund

`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.

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Michele R. Warmund

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.

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Michele R. Warmund and Joan Krumme

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.

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Michele R. Warmund and Denny Schrock

Master Gardener training was delivered via interactive television (IT) or face to face (FTF) in Missouri in 1997. IT and FTF participants were surveyed on their acceptance of the Master Gardener training method and their perceptions of program quality and technology to evaluate the newly developed multiple site IT training. Demographic characteristics were also recorded to determine if IT format attracted a different clientele than that of FTF training. Those who participated in IT training generally had more years of education than those in the FTF training and lived in suburban rather than rural areas. IT participants missed fewer training sessions than FTF participants. However, IT participants rated the slide quality, sound, and overall training lower than the FTF group. Some problems associated with IT training identified by the participants are correctable, which should improve future acceptance of this technology.

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Michele R. Warmund and James T. English

In 1993, ice-nucleation-active (INA) bacteria were isolated from `Redwing' red raspberries (Rubus idaeus L. var. idaeus) at five pigmentation stages. Fruit were also subjected to thermal analysis to determine the ice nucleation temperatures. INA bacteria were recovered from nearly all fruit samples, and the bacterial populations tended to decrease with greater red color development (i.e., fruit maturation). However, the ice nucleation temperature was not affected by the stage of fruit pigmentation. In 1994, INA bacterial densities were similar among fruit at the three pigmentation stages sampled. INA bacteria were recovered more often from the calyx rather than the drupe surface of these fruit. INA bacteria also were detected on pistils of some fruit. Red and pink fruit, which were nucleated with ice, had greater receptacle injury than mottled, yellow, or green fruit, but INA bacterial densities apparently were not related to injury. Thus, the injury response of fruit at different pigmentation (or development) stages indicated that nonbacterial ice nuclei may be involved in freezing injury of developing raspberries.

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Michele R. Warmund and James T. English

INA bacteria were isolated from primary flowers of `Totem' strawberry (Fragaria ×ananassa Duch.) plants that had been previously inoculated with strain Cit 7 of Pseudomonas syringae van Hall or noninoculated to determine their relationship to ice-nucleation temperature and floral injury. Mean ice-nucleation temperature of inoculated and noninoculated flowers was -2.2 and -2.8 °C, respectively. Primary flowers of noninoculated plants survived lower temperatures than those of inoculated plants. In another experiment, noninoculated plants were misted with sterile deionized water and incubated for 0, 12, 24, 36, or 48 hours at 25 °C day/10 °C night, and naturally occurring INA bacteria were isolated from primary flowers. INA bacterial densities increased exponentially with increasing incubation period. The critical wetness period for INA bacteria to establish a sufficient density to increase the likelihood of floral injury at -2.5 °C was 24 hours. Longer wetness periods resulted in higher INA bacterial densities but did not increase the floral mortality rate. Thermal analysis demonstrated that the ice nucleation temperature was associated with strawberry floral injury. Thus, low temperature survival of flowers was adversely affected by moisture for ≥24 h due to the presence of a sufficient density of INA bacteria to incite ice formation and floral injury.

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Michele R. Warmund and James T. English

Cryoprotectants were applied at labeled rates to primary flowers of `Honeoye' strawberry (Fragaria × ananassa Duch.) plants at full bloom to determine their effects on the floral organs. Frostgard at 50 ml/liter or KDL at 22 ml/liter injured pistils and resulted in misshapened fruit. Floral buds that were closed when cryoprotectants were applied were uninjured. In other experiments, efficacies of cryoprotectants were determined after floral tissues of `Honeoye' strawberry plants were inoculated or not inoculated with the ice-nucleation-active (INA) bacteria, Pseudomonas syringae van Hall and subjected to sub-freezing temperatures. None of the products protected primary or secondary flowers against freezing injury regardless of the occurrence of INA bacteria. INA bacteria were not recovered from primary flowers of treated plants that were killed by low temperature exposure, indicating that non-bacterial nuclei may incite freezing in these tissues.

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Michele R. Warmund and James T. English

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.