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Peet et al. (1997) demonstrated that in male-sterile tomato plants (Lycopersicon esculentum L. Mill cv. NC8288) (MSs) provided with pollen from male-fertile plants (MFs) grown at 24°C daily mean, percent fruit set, total number and weight of fruit, and relative seediness decreased linearly as mean daily temperature rose from 25 to 29°C. The primary parameter affecting these variables was mean temperature, with day temperature at a given night temperature, night temperature at a given day temperature, and day/night temperature differential having secondary or no effect. To compare the effect of temperature stress experienced only by the female tissues with that experienced by the male tissues or both male and female tissues, MSs and MFs were grown in 28/22°C, 30/24°C, and 32/26°C day/night temperature chambers. Fruit yield and seed number per fruit declined sharply when increased temperatures were experienced by both male and female tissues (MFs). There was no fruit set in any of the MSs assigned to the 32/26°C pollen treatment, mostly because of the limited amount of pollen available from MFs. Both fruit production and seed content per fruit were also greatly reduced in MSs receiving pollen from 30/24°C grown MFs for the same reason. For plants experiencing stress only on female tissues (MSs grown at high temperatures, but receiving pollen from MFs grown at the lowest temperature), there was also a linear decrease in fruit yield as growth temperatures increased, as previously seen by Peet et al. (1997), but the temperature effect was less pronounced than that on pollen production. Thus, for this system, temperature stress decreased yield much more drastically when experienced by male reproductive tissues than when experienced only by female reproductive tissues.

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Leaf gas-exchange and chlorophyll fluorescence measurements were used as indexes for evaluating heat tolerance among five taxa of birch: paper (Betula papyrifera Marsh.), European (B. pendula Roth.), Japanese (B. platyphylla var. japonica Hara. cv. Whitespire), Himalayan (B. jacquemontii Spach.), and river (B. nigra L. cv. Heritage). Gas-exchange measurements were conducted on individual leaves at temperatures ranging from 25 to 40C. River birch maintained the highest net photosynthetic rates (Pn) at high temperatures, while Pn of paper birch was reduced the most. Further study of river and paper birch indicated that the reduced Pn at high temperatures and the differential sensitivity between taxa resulted from several factors. Inhibition of Pn at higher temperatures was due largely to nonstomatal limitations for both taxa. Increases in respiration rates, decreases in maximal photochemical efficiency of photosystem (PS) II (F V/F M), and possible reductions in light energy directed to PS II (F 0 quenching) were apparent for both taxa. The capacity of river birch to maintain greater Pn at higher temperatures seemed to result from a lower Q10 for dark respiration and possibly greater thermotolerance of the Calvin cycle as indicated by a lack of nonphotochemical fluorescence quenching with increasing temperatures. Thermal injury, as indicated by a rapid increase in minimal, dark-acclimated (F 0) fluorescence, was not evident for either paper or river birch until temperatures reached ≈49C and was similar for both taxa.

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Lycopersicon esculentum Mill. `Laura' plants were grown in the North Carolina State Univ. phytotron at 26C day temperature and 18, 22, 24, or 26C night temperatures to determine the effects of night temperature on pollen characteristics, growth, fruit set, and early fruit growth. Total and percentage normal pollen grains were higher in plants grown at night temperatures of 18 and 22C than at 24 and 26C, but germination was highest in pollen produced at 26C. Seed content was rated higher on the plants grown at 18C night temperatures than in any of the other treatments. Numbers of flowers and fruit on the first cluster were lower in the 26C night treatment than in the other night temperature treatments. Plant height was greatest but total shoot dry mass was lowest in the 22C night temperature treatments. Fruit fresh mass increased with night temperature, reflecting more rapid development, but the experiment was not continued to fruit maturity, so the effect of night temperature on final fruit size and total plant production could not be determined. Night temperatures of 26C reduced fruit number and percentage fruit set only slightly at a day temperature of 26C, even though these temperatures were above optimal for pollen production and seed formation. To separate temperature effects on pollen from direct or developmental effects on female reproductive structures, pollen was collected from plants in the four night temperature treatments and applied to stigmas of a male-sterile cultivar kept at 24-18C minimum temperatures in adjacent greenhouses. In the greenhouse-grown male sterile plants, no consistent effects of night temperature treatment given the pollen could be seen in fruit set, fruit mass, seed content (either on a rating or seed count basis), seedling germination, or seedling dry mass.

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Previous greenhouse studies in Raleigh have shown that nighttime cooling increases tomato fruit weights from 11% to 53%, depending on planting dates. The physiological mechanism was unclear, except that temperatures during fruitset were most critical. We report here on 3 experiments, 2 in greenhouses and 1 in the phytotron, comparing pollen characteristics of plants grown at differing night temperatures. In the greenhouse studies, nighttime temperatures were kept below 20°C for either the whole night or just the last half of the night. In the phytrotron studies night temperatures were 18, 22, 24 or 26°C, In both phytotron and greenhouse studies, there was considerable day-to-day variability in pollen characteristics and % germination. The most consistent effect in both types of studies was a decrease in total pollen and an increase in % abnormal pollen at high night temperatures. In the phytotron studies 20°C appeared optimal for both these characteristics.

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Research was initiated at the N.C. State Univ. Horticultural Field Laboratory, Raleigh, to identify cultural practices and tomato cultivars giving superior taste under North Carolina greenhouse conditions. The specialty cultivars `67', `Diana', `Elegance', `Momotaro', and `S630' were grown and harvested, as well as `Trust', which is grown on 85% of the North American greenhouse tomato acreage. Additionally, two fertilizer regimes were provided to the plants: standard greenhouse tomato fertilization (EC ≈1.75 dS·m-1) or high fertilization (EC ≈3.75 dS·m-1). Fertilizers were the same in both treatments. Seeds were started in October 2002 and transplanted, 2 per pot, into `Bato' buckets containing perlite in November. Standard cultural practices were followed, and plants were fertigated using the Harrow Fertigation Manager™ system. Taste tests conducted on three dates revealed differences among cultivars, with `67', `Elegance' and `Momotaro' consistently scoring well. Overall, all test varieties were scored higher than `Trust'; however flavor was somewhat less sweet than anticipated, especially early in the season, averaging 2-3 on a scale of 5, where 5 was “best”. No significant differences were seen between the standard and high fertilization treatments. Differences in total harvest weight were seen among cultivars. `Elegance' and `67' produced fruit consistently well through the harvest season, while the remaining cultivars' yields were sporadic. Harvested fruit were homogenized, and Brix was measured as an indicator of fruit quality. Significant differences in Brix were seen among the cultivars, with `67' significantly higher than all other varieties and `Elegance' and `Momotaro' higher than the remaining cultivars. All specialty cultivars had higher °Brix than `Trust'.

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Many potential students, because of distance from the university campus and/or job requirements, cannot take traditional courses on-campus. This group of learners is “place-bound”—a group of learners who may be employed full-time, most likely married with job responsibilities and/or other situations demanding most of their attention. The Horticultural Science Department and Graduate School at N.C. State University are addressing place-bound limitations in several ways, including the creation and offering of a Graduate Certificate Program in Horticultural Science via distance education (DE). By using DE, high demand, low-seat-available classes can offer additional enrollment for credit. Second, courses can be offered asynchronously or with alternative delivery methods. Also, courses offered collaboratively among institutions can generate a level of interest and enthusiasm that may not exist for “home-grown” courses. Such efforts as these promise to help meet continuing education demands of “non-traditional” students. These include Cooperative Extension's more than 120 Horticultural Crops Extension Agents (“field faculty”) and over 300 other field faculty whose interests include horticultural topics.

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Organic and heirloom tomatoes are high-value products with growing demand but there are many challenges to successful cultivation. A systems comparison study was carried out to evaluate the production of the popular heirloom tomato ‘Cherokee Purple’ (Solanum lycopersicum L.) under high tunnel and open field systems in North Carolina from 2007 to 2008. Management of the high tunnel (i.e., temperature and irrigation), weather events as well as pest and disease pressure influenced crop quality and yield. The high tunnel and field systems achieved similar total yields (100 t·ha−1) the first season but yields were 33% greater in the high tunnel system than the field system in the second year (100 t·ha−1 and 67 t·ha−1, respectively). Both years, the tomatoes were planted in high tunnels 1 month earlier and harvested 3 weeks earlier than the field. The accumulation of ≈1100 growing degree-days (GDD) was required in both systems before 50% of the fruit was harvested. Fruit cracking, cat-facing, blossom-end rot, and insect damage were the major categories of defects in both systems. Incidence of both Tomato Spotted Wilt Virus (TSWV) and Gray Leaf Spot (GLS) were lower in the high tunnel compared with the field in 2007 and 2008, respectively. Results of this study suggest that with proper management techniques, high tunnels can optimize yields, increase fruit quality, and provide season extension opportunities for high-value horticultural crops.

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Abstract

Crack-susceptible and crack-resistant tomato (Lycopersicon esculentum L. Mill.) cultivars were grown in soil beds and in bags filled with a peat-vermiculite mix. Plants in soil were drip-irrigated 1 or 4 times daily, or hand-watered every day or as needed based on soil moisture tension. Plants in bags received only drip-irrigation treatments. Genotype had the greatest effect on fruit cracking, with 3.8% by weight cracked fruit in the crack-resistant compared to 35.3% in the crack-susceptible cultivar. Growing plants in bags reduced the weight and the percentage of cracked fruit per plant, but, in both cultivars, total and No. 1 fruit weights were greatest from the soil treatments with drip-irrigation. Irrigation frequency and method did not affect fruit weight except in the crack-resistant cultivar grown in bags where increasing irrigation frequency increased weights. Cracking was decreased by 22% in tomatoes irrigated manually every day, compared to those irrigated only when needed. In the soil treatment, raising the irrigation frequency significantly decreased cracking in the susceptible, but not in the resistant cultivar. In the soilless treatment, frequent irrigation increased cracking in both cultivars.

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Eight tomato (Lycopersicon esculentum) cultivars were grown for 16 weeks in greenhouses enriched for an average of 8.1 hours daily to 1000 μl CO /liter of air or in greenhouses maintained at ambient CO. Carbon dioxide enrichment significantly decreased the mean number of greenhouse whiteflies [Trialeurodes vaporariorum (Westward), Homoptera: Aleyrodidae] as measured by counts from commercial yellow sticky traps. The number of whiteflies present was negatively correlated with both seasonal foliar C: N ratio and percent C but positively correlated with percent N in the foliage. Thus, CO enrichment apparently alters plant composition in such a way as to reduce significantly the population growth of greenhouse whiteflies.

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The grafting of herbaceous vegetables is an emerging development in the United States. This report provides an estimate of the variable costs of grafting within U.S. tomato (Solanum lycopersicum) transplant production systems. Grafted and nongrafted plants were propagated at two commercial farming operations in Ivanhoe, NC (NC) and Strasburg, PA (PA) and the farm in NC produced certified organic transplants. Detailed economic production sequences were generated for each site, and grafted and nongrafted transplant production costs were $0.59 and $0.13 in NC, and $1.25 and $0.51 in PA, respectively. Direct costs associated with grafting (e.g., grafting labor, clips, chamber, etc.) accounted for 37% to 38% of the added cost of grafting, and grafting labor was 11.1% to 14.4% of the cost of grafted transplant production. Seed costs represented 52% and 33% of the added cost of grafting at the two sites, and indirect costs (e.g., soil, trays, and heating) accounted for 10% and 30% of the added cost of grafting. Our findings suggest that under current seed prices and with similar production practices, the feasibility of grafting in the United States is not disproportionately affected by domestic labor costs. Additionally, the economic models presented in this report identify the cost of production at various transplant stages, and provide a valuable tool for growers interested in grafted tomato transplant production and utilization.

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