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There is growing demand for food grown and sold locally, but climate often limits supply. High tunnels can often overcome these limitations. In order to encourage local availability and production of specialty crops the Natural Resource Conservation Service (NRCS) has launched the Seasonal High Tunnel initiative. This cost-share program provides farmers with a high tunnel intended to encourage the availability of locally grown fresh produce. Using mixed-methods research this thesis examines the social, economic, and conservation impacts of the NRCS high tunnel program. We have run a county by county negative binomial regression of the NRCS high tunnel distribution biophysical, socio-demographic, and market driven factors. Additionally, 7 vegetable farms throughout Virginia were visited during the 2014 growing season to compare high tunnel and field grown cucumbers (Cucumis sativus) and tomatoes (Solanum lycopersicum). Additional detail about high tunnel production and food distribution was obtained with a survey of Virginia high tunnel growers. Survey respondents indicate that the majority of their high tunnel produce is sold within 100 miles of their farm. Regression results indicate that the NRCS high tunnel program is benefiting areas where the availability of local food is high, but may be neglecting areas with historically underserved communities. Our field results show that yield and the yield per pesticide application dividend were higher in high tunnel production of both cucumber and tomato. Therefore, we conclude that, high tunnels meet conservation goals different than the ones outlined by the NRCS. The NRCS high tunnel program is promoting the expansion of local food availability. However, work remains to clarify conservational benefits and to ensure that all communities have equal access to the fresh produce they provide. / Master of Science

Tomato fruit have been associated with numerous outbreaks of salmonellosis in recent years. Trace back suggests tomato fruit may become contaminated during pre-harvest, however exact routes are unclear. The objective of this study was to determine the potential for Salmonella enterica serotype Newport to be associated with the roots, leaves, stems, and ultimately fruit of red round tomato plants through contaminated irrigation water, at various stages of plant development, when grown under controlled environmental conditions. Tomato plants were individually root irrigated with 250 or 350 ml (depending on growth stage) of 7 log CFU/ml S. Newport contaminated irrigation water every seven days. Presence of the pathogen in plant tissue was evaluated at five growth stages; 14 days post transplant, early fruit, mid fruit, full fruit, and terminal stages. At each stage, roots, stems, leaves, and two tomato fruit, if present, from four S. Newport and four water irrigated (negative control) tomato plants were sampled for S. Newport contamination. Association of S. Newport was detected in tomato roots and stems using both conventional plating and molecular techniques. Twenty-four samples were confirmed positive for S. enterica using PCR. Sixty-five percent of the roots, 40% of the stems, 5% of the leaves and 5% of the fruit sampled were confirmed to contain S. enterica. Overall, there was significant difference in the presence of S. Newport according to tissue sampled (roots > stems > leaves and fruit) (P > 0.05). There was no correlation between growth stage and presence of S. Newport in tissues (P > 0.05). Ultimately, irrigation with S. Newport has a low probability of contaminating tomato fruit. / Master of Science

The impacts of climate change on agriculture have been observable for years, particularly with declining yields and reduced productivity. Much research has been performed to examine the relationships between yield and climatic variables, especially temperature and precipitation. By comparison, little research has been conducted to assess the impact that climate change has on the nutrition, particularly the antioxidant content and capacity, of crops. This research project aims to fulfill this knowledge gap. Solanum lycopersicum cv. Micro-Tom plants were cultivated in five growth chambers with different temperatures, hours of light, and watering regimes to simulate different environments. The three temperature regimes were 25°, 32°, and 40°C during the day. The two chosen light durations were 12 and 16 hours (h), and the selected watering frequencies were 3 and 5 days (d). Lycopene and phenolics were quantified via spectrophotometry. Color was assessed via the CIELAB color space, specifically the a* value. The ferric reducing ability of plasma (FRAP) assay assessed the ability of the compounds in each tomato sample to serve as antioxidants. Upon analysis, the highest lycopene concentration (72.68 mg per kg fresh weight) was found in tomatoes exposed to 32°C, three days between irrigation cycles, and 16 hours of light. The highest level of phenolics (0.41660 mg gallic acid equivalent per g fresh weight) was observed in tomatoes exposed to 32°C with three days between watering cycles. The largest a* value (11.21), which corresponds to an intense red hue, was seen in tomatoes exposed to 32°C with 16 hours of light. The greatest level of antioxidant capacity [162.12 micromolar Fe(II)] as measured by the FRAP assay occurred in tomatoes exposed to 32°C with three days between irrigation cycles. Overall, antioxidant content and capacity increased the most at 32°C with three days between watering periods. Photoperiod was unimportant. By varying environmental conditions, “designer crops” with specific antioxidant content can seemingly be produced without genetic manipulation. This work enhances the body of knowledge concerning effects of abiotic stress on food crop antioxidants, which is important given the gravity of climate change.

The transmission properties, host range, and virus- vector relationships of chino del tomate virus (CdTV), a new whitefly-transmitted geminivirus of tomato, are described. The virus is transmitted by B. tabaci, the sweet potato whitefly, but not by seed or sap. The virus infects members of the Asclepiadaceae, Leguminosae, Malvaceae, and Solanaceae. In virus-vector studies, minimum AAF and IAF times were 1 hour and 2 hours, respectively. The virus was retained by its whitefly vector for 4.5 and 7.3 days following 24- and 72-hr AAF respectively. Relative efficiencies of transmission for 1, 5, 10 and 20 B. tabaci were 15, 49, 84 and 100 percent, respectively. The chino del tomate (CdT), or leaf curl disease of tomato (Lycopersicon esculentum Mill.), was first reported in cultivated tomato fields in Sinaloa, Mexico in 1970-71 (4). Presently, it occurs in tomato production areas of the west coast of Sinaloa and may affect 100 percent of the plants in a field (1). The disease is characterized by curled and rolled leaves, thickened veins, a bright-to-subdued-yellow mosaic which varies with time of the year, stunting, and a reduced fruit set (1,3). Recently, a whitefly -transmitted geminivirus, CdT virus (CdTV), was implicated as the causal agent of the disease (1,3), but information concerning the biological nature of the virus is lacking. Here, we present the results of studies involving virus transmission, experimental host range, and virus -vector relationships.

Thesis (Ph. D.)--University of California, Davis, 1987. / Includes bibliographical references (leaves 237-253).

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