Browsing by Author "Lowman, James Scott"

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    Dwarf Tomatoes in an Indoor Vertical System
    Tharpe, Anna Ekene Davis (Virginia Tech, 2023-06-05)
    An experiment was conducted to evaluate the potential of producing dwarf tomatoes (Solanum lycopersicum L.) in an indoor vertical system. Cultivars 'Micro Tom', 'Jochalos', and 'Venus' were grown under the three daily light integral (DLI) levels of 16.9, 22.7, and 27.9 mol·m-2·day-1. Cultivar had an effect on height, with Jochalos being the tallest. Plants grown under 27.9 mol·m-2·day-1 were the shortest. The time of first flower was affected by cultivar, appearing earliest in Micro Tom. Regarding DLI, the first flower was earliest in plants under 22.7 and 27.9 mol·m-2·day-1. The time of first harvest was only affected by cultivar, in which Micro Tom was earliest. There was an interaction effect for the total and marketable fruit count harvested. Micro Tom had the highest overall number of fruits harvested amongst cultivars, and Micro Tom grown under 22.7 and 27.9 mol·m-2·day-1 had more total and marketable fruit counts than those grown under 16.9 mol·m-2·day-1. There was no interaction effect for fruit weight harvested. The effect of cultivar differed between the total and marketable fruit weights harvested, but Jochalos produced the highest weights in both. The effect of DLI was the same for total and marketable fruit weights harvested, with plants under 22.7 and 27.9 mol·m-2·day-1 having the highest weights. Cultivar had an effect on fruit Brix, with Micro Tom fruit having the lowest Brix and Jochalos fruit having the highest Brix. The effect of DLI resulted in fruits produced by plants under 27.9 mol·m-2·day-1 having the highest Brix and fruits produced by plants under 16.9 mol·m-2·day-1 having the lowest. Based on these results, there is potential for dwarf tomatoes to be grown in vertical farm systems.
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    Growth promotion and colonization of switchgrass (Panicum virgatum) cv. Alamo by bacterial endophyte Burkholderia phytofirmans strain PsJN
    Kim, Seonhwa; Lowman, James Scott; Hou, Guichuan; Nowak, Jerzy; Flinn, Barry; Mei, Chuansheng (2012-05-30)
    Background Switchgrass is one of the most promising bioenergy crop candidates for the US. It gives relatively high biomass yield and can grow on marginal lands. However, its yields vary from year to year and from location to location. Thus it is imperative to develop a low input and sustainable switchgrass feedstock production system. One of the most feasible ways to increase biomass yields is to harness benefits of microbial endophytes. Results We demonstrate that one of the most studied plant growth promoting bacterial endophytes, Burkholderia phytofirmans strain PsJN, is able to colonize and significantly promote growth of switchgrass cv. Alamo under in vitro, growth chamber, and greenhouse conditions. In several in vitro experiments, the average fresh weight of PsJN-inoculated plants was approximately 50% higher than non-inoculated plants. When one-month-old seedlings were grown in a growth chamber for 30 days, the PsJN-inoculated Alamo plants had significantly higher shoot and root biomass compared to controls. Biomass yield (dry weight) averaged from five experiments was 54.1% higher in the inoculated treatment compared to non-inoculated control. Similar results were obtained in greenhouse experiments with transplants grown in 4-gallon pots for two months. The inoculated plants exhibited more early tillers and persistent growth vigor with 48.6% higher biomass than controls. We also found that PsJN could significantly promote growth of switchgrass cv. Alamo under sub-optimal conditions. However, PsJN-mediated growth promotion in switchgrass is genotype specific. Conclusions Our results show B. phytofirmans strain PsJN significantly promotes growth of switchgrass cv. Alamo under different conditions, especially in the early growth stages leading to enhanced production of tillers. This phenomenon may benefit switchgrass establishment in the first year. Moreover, PsJN significantly stimulated growth of switchgrass cv. Alamo under sub-optimal conditions, indicating that the use of the beneficial bacterial endophytes may boost switchgrass growth on marginal lands and significantly contribute to the development of a low input and sustainable feedstock production system.
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    Optimizing Hydroponic Lettuce Yield: Evaluation of Potassium Source and Concentration with Plant Imaging
    Doss, Mitchell C. (Virginia Tech, 2024-10-15)
    Controlled Environment Agriculture (CEA) is an expanding industry in the United States. Lettuce (Lactuca sativa) possesses considerable economic importance as one of the foremost leafy vegetables worldwide in terms of financial value for production in CEA. Rapid growth rate, high yield, and potential return further enhance its suitability for cultivation within CEA. Pursuing optimal and sustainable nutrient concentrations for crops in CEA is a continuous requirement for an expanding industry. This study is set to investigate the impact of different potassium (K) sources and concentrations on 'Green Oakleaf' lettuce growth. The K concentration within the Virginia Tech base hydroponic lettuce fertilizer was increased,1x, 2x, and 3x the normal rates of K ppm, through the addition of potassium chloride (KCl) or potassium sulfate (K2SO4). To account for rising electrical conductivity (EC), due to the increase of K, KCl treatments were recreated with standardized EC through the addition of Sodium Chloride (NaCl). The Spatially and Mechanically Accurate Robotic Table (SMART) in an indoor space was utilized to cultivate and image plant growth over time through pixel count. Growth index and chlorophyll content were recorded weekly, while the fresh weight and dry weight of shoots were recorded at harvest. The KCl treatment with the highest concentration,4x K ppm, as well as those with standardized EC, led to reduced yield when compared to other treatments. All K2SO4 treatments showed no difference in growth when compared to the base solution. K source and concentration, as well as fertilizer EC, were all identified as factors influencing the impact of fertilizers on the optimization of lettuce yield.
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    SmartPlants and SmartFarms for Global Food, Feed, and Fiber Security
    Abaye, Azenegashe Ozzie; Balota, Maria; Bombarely Gomez, Aureliano; Clark, Susan F.; Evanylo, Gregory K.; Fox, Thomas R.; Grabau, Elizabeth; Haak, David C.; Holliday, Jason A.; Kroehler, Carolyn J.; Lowman, James Scott; McDowell, John M.; Raun, Patricia; Saghai-Maroof, Mohammad A.; Schmale, David G. III; Tholl, Dorothea; Thomason, Wade E.; Tokekar, Pratap; Veilleux, Richard E.; Vinatzer, Boris A.; Westwood, James; Wynne, Randolph H.; Zhao, Bingyu (Virginia Tech, 2017-05-15)
    Meeting the food, feed, and fiber needs of a growing world population represents one of the signature challenges of this century. The UN FAO estimates that food production alone must increase by 70 percent by 2050 to meet the needs of a projected nine billion people. Demand will also increase for livestock feed, biofuel feedstocks, fiber for paper products, and construction materials. Meeting these demands will require implementation of advanced technologies, sustainable management of natural resources, and coordination of political forces. We must think beyond the boundaries of traditional agriculture, to integrate breakthroughs in plant science, engineering, environmental sciences, and other disciplines...
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    Utilizing Beneficial Bacterial Endophytes to Promote Switchgrass Growth in Low- input Agricultural Production Systems
    Lowman, James Scott (Virginia Tech, 2014-02-20)
    The US Department of Energy has focused research efforts on developing switchgrass into a bioenergy feedstock, helping to offset the use of non-renewable fossil fuels and make the US more energy independent. Bacterial endophytes, which reside inside plant tissues, are proven to increase yield and stress resistance in a number of plants. The primary objective of this dissertation was to explore the use of endophytes to improve biomass yields of switchgrass on lands not suitable for food crops and better understand the underlying mechanisms of the plant-endophyte interaction. Integration of this research into K-12 STEM education to increase interest in plant sciences and create the next generation of scientists with the motivation to help solve the challenges facing society in the twenty first century was the objective of the outreach component of this project. Chapter one demonstrates the ability of Burkholderia phytofirmans strain PsJN to colonize switchgrass and promote plant growth under in vitro (approximately 50% higher), and growth chamber and greenhouse (48.6% higher biomass yields) conditions. The objectives of Chapter two were to determine stand establishment in the field with different nutrient levels. PsJN bacterization positively benefited growth and development of switchgrass seedlings in the field with both low and high nutrient content. Highly significant (p<0.001) stimulation of root and shoot growth, lateral root formation and number of tillers was recorded on soil with low fertility. PsJN bacterization also enhanced biomass accumulation during the two seasons of growth on both poor (p<0.001) and rich (p<0.05) soil, indicating the potential for the use of PsJN in a low-input switchgrass feedstock production system. Chapter three outlines differences in gene expression patterns upon bacterization, between the responsive cv. Alamo, and a non-responsive cv. Cave-in-Rock. Using EST microarrays and quantitative PCR up- and down-regulated genes were identified in both cultivars. One of the key genes identified was a member of the tau class, glutathione S-transferase (GST). GST enzymes are known to be involved in plants responses to stress. Using overexpression and knockout/knockdown techniques we demonstrated that GST is likely involved in the bacterization induced early plant growth promotion in switchgrass. Chapter four describes the potential for the utilization of beneficial bacterial endophytes capable of fixing atmospheric nitrogen in a free-living state in the development of low-input switchgrass feedstock production systems. Sphingomonas sp. strain NSL isolated from switchgrass tissue was able to grow on nitrogen free medium and stimulated growth of switchgrass cv. Alamo under nitrogen deficient conditions. The ability to fix atmospheric nitrogen was also moved to Burkholderia phytofirmans strain PsJN via horizontal gene transfer from the legume nodulating Burkholderia phymatum. The transformed PsJN was able to fix nitrogen and promote plant growth under nitrogen limited conditions. At every step of the research described in this dissertation efforts were made to include its elements into K-12 education. Chapter five describes four case studies aiming at the enhancement of youth interest in plant sciences in the socieoeconomically depressed areas of Southside Virginia.