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Racheff Chair

Professor Neal Stewart | Projects | Course Documents | People

The Ivan Racheff Chair of Excellence was established in 1987 to honor the late Ivan Racheff, owner of Knoxville Iron Works, now AmeriSteel, and recognizes excellence in both teaching and research in the materials science and engineering disciplines.

Professor Charles “Neal” Stewart assumed the Ivan Racheff Chair of Excellence in Plant Molecular Genetics in 2002. Stewart and his laboratory conduct research in plant molecular genetics, plant biotechnology, risk assessment, and biofuel. The team performs agricultural biotechnology and risk assessment research. This work has been supported by various granting agencies including the Defense Advanced Research Projects Agency and various other US military agencies, Department of Agriculture, Department of Energy, Environmental Protection Agency, National Aeronautics and Space Administration, and National Science Foundation.​​​ ​

leafy green plants sit inside a tray of seedlings labelled with purple tags inside a grow chamber

Racheff Chair of Excellence in Plant Molecular Genetics | 320 Plant Biotechnology Building | 2505 E J Chapman Drive | Knoxville, Tennessee 37996


Neal Stewart, Department of Plant Sciences professor, holds the Ivan Racheff Chair of Excellence in Plant Molecular Genetics. He also serves as co-director of the Center for Agricultural Synthetic Biology, which Stewart co-founded in 2018. After completing a Doctorate of Biology in Plant Physiology at Virginia Tech, Stewart joined Professor Wayne Parrott’s laboratory at the University of Georgia as a postdoctoral researcher from 1993 – 1995. He then moved to the University of North Carolina at Greensboro where Stewart was an assistant and then associate professor in the Department of Biology from 1995 – 2002. In 2002, Stewart assumed the Racheff Chair with an appointment as professor.

Stewart has authored or co-authored over 310 journal articles, many book chapters, and nine books. He is co-editor in chief for Plant Cell Reports and is an associate editor for the Plant Biotechnology Journal. Stewart was elected as an American Association for the Advancement of Science fellow in 2015, a Society for In Vitro Biology fellow in 2019, and from 2014 – 2016, served on the National Academies committee responsible for publishing “Genetically Engineered Crops: Experiences and Prospects” in 2016.

Stewart’s research has been supported by various granting agencies including the DARPA, DOE, NSF, USDA, and industry sources. Of the approximately $40 million awarded over the past 25 years in grants and contracts, 5% has had industry ties.

Stewart teaches courses in biotechnology and research ethics. He has mentored over 100 graduate and postdoctoral students and technical staff, most of whom are still in science. Stewart has given scientific and lay presentations around the US and in 16 countries. 

Stewart’s hobbies include those in the bioenergy and transportation sectors and boating and swimming in the Tennessee River. Stewart is also a singer-songwriter whose songs can be found on ReverbNation.


Stewart also co-directs the Center for Agricultural Synthetic Biology.

Projects

Close up of pollen from genetically engineered switchgrass, green clumps on a Petri dish.
Close up of pollen from genetically engineered hemp, green clumps on a Petri dish.

Funded by the Department of Agriculture Biotechnology Risk Assessment Research Grants Program

This project focuses on having a validated and reliable long-distance transport prediction model for wind-dispersed pollen is critical to establishing appropriate isolation distances for genetically engineered crops and making informed regulatory decisions. Switchgrass and hemp are primarily wind-pollinated crops. The specific objectives of our proposed research are to develop and test new methods with unmanned aircraft systems (UAS or drones) for monitoring wind-dispersed pollen from genetically engineered crops, generate and validate a large eddy simulation (LES) model to track the long-distance transport of genetically engineered pollen, and predict the regional transport of wind-dispersed pollen using the LES model. Genetically engineered switchgrass and hemp, in which pollen is marked with genetically-encoded fluorescent proteins, will be grown at a unique field site in Tennessee. This work is being done in collaboration with Assistant Professor Hosein Foroutan, Professor Shane Ross, and Professor David Schmale laboratories at Virginia Tech. 

a drone photo over a field of stands of switchgrass with a green field and buildings in the background with a blue cloudy sunny sky

Funded by the Center for Bioenergy Innovation

This project focuses on increasing the yield and sustainability of plant feedstocks, which emphasizes the importance of performing field studies for improvement of biofuel yield without negative consequences to biomass production or sustainability. Our study supports a genome-wide association study (GWAS) in switchgrass under field condition to enable rapid domestication and increased sustainability in feedstock. The study also involves the development of unmanned aerial vehicle (UAV)-based remote sensing for switchgrass high-throughput phenotyping in the field. The UAV-based approach facilitates identification of superior genotypes. Using a GWAS approach, many measurements, including growth, composition and biomass convertibility, of the broad variation across the switchgrass population can be correlated with specific genes. The use of the natural variation and identification tools in the GWAS switchgrass studies allow rapid identification of gene candidates. Our established GWAS field enables rapid discovery of environmentally stable genetic controls. This will lead to the identification of important genetic regulators of biomass recalcitrance and other plant traits bringing the increased yield and sustainability in long-lived perennial switchgrass.

Funded by the Tennessee Soybean Promotion Board

This project focuses on soybean plants with increased root length and branching to boost yield and durability. A strong root system is necessary for maximized plant nutrition, defense, and water use. Soybean plants with increased root length and branching would significantly improve water and nutrient uptake efficiency and yield potential in diverse environments. Such improvement is the primary goal of this project. For that, the key soybean genes involved in root growth and development are identified. The candidate root growth genes are initially assessed in transgenic soybean hairy root system. Subsequently, the novel root genes are evaluated in genetically-modified stable soybean plants for their impact on root growth, soybean productivity, and stress tolerance to challenging environmental conditions. We expect that the discovery of the novel root-important genes identified in the present study will lead to the production of soybean with deeper and more extensive root systems. In turn, these plants will have improved performance and yield, particularly under conditions of limited water and nutrient availability. The present study provides a basis for development of soybean lines with improved growth and tolerance to abiotic stresses. The result should facilitate a roadmap for breeding and developing high yielding soybean varieties.

Infographic of plant soybean plant with above text, "plant over expressing protease-inhibitor protein," with arrows pointing to a column called hypothesized expression with three pictures. The first is a worm eating a leaf with the text, "Protease-inhibitor protein will either kill insect or reduce leaf feeding." The second has one larger rat with a second slimmer rat with the text, "Reduction in rat weight gain in the presence fo protease-inhibitor protein in diet." And third a microscopic look of a nematode, which looks like a clear worm, with text, "Prevent or reduce soybean cyst nematode infection."

Funded by the Tennessee Soybean Promotion Board

The project focuses on producing genetically engineered soybean for deer resistance traits. All legume seeds produce trypsin inhibitors as well as other protease inhibitors that can hinder mammalian digestive enzymes. Mature seeds must be treated by heat or chemicals to deactivate these protease inhibitor proteins that are found in soybean meals. Soybean, therefore, already has a built-in deterrent to feeding by mammals in the seed. The goal of this project is to produce trypsin inhibitors in soybean leaves with high expression. For that, 6 different Kunitz trypsin inhibitor genes and 1 Bowman-Birk inhibitor gene have been selected. These genes will be evaluated in genetically engineered soybean plants to determine their inhibitory impact on the mammalian digestive system. Since deer are adept learners, it is hypothesized they would learn to avoid eating soybean leaves. Additionally, Kunitz trypsin inhibitor inactivates trypsin enzyme, which is the common digestive enzyme found in lepidopteran insects. The transgenic soybean lines will also be evaluated against leaf-feeding insects to determine their impact on insect growth as well as the decrease of leaf defoliation. The present study will alter trypsin inhibitor expression in soybean leaves with an increased inhibitory effect on mammalian and leaf defoliator digestive systems.

Course Documents

PLSC 452/552 — Plant Biotechnology and Genetics


A course on genetic principles and techniques used in plant modification and principles of molecular and transmission quantitative genetics as applied to plant biotechnology. Prerequisites include BIOL 111 and 112. 

SYLLABUS

LECTURE SLIDES – Stewart, C.N., Jr. (Ed.) 2008. Plant Biotechnology and Genetics: Principles, Techniques and Applications, John Wiley & Sons, Hoboken, New Jersey: 374 pp. (FIRST EDITION)

LECTURE SLIDES – Stewart, C.N., Jr. (Ed.) 2016. Plant Biotechnology and Genetics: Principles, Techniques and Applications, Second Edition, John Wiley & Sons, Hoboken, New Jersey: 406 pp. (SECOND EDITION)

a student in baseball hat and t shirt speaks as they sit at a table in a classroom
Research Ethics for Scientists: A Companion for Students book cover with a blue background with a light and hand grabbing a beaker from a stand in shadow with white text overlayed

Research Ethics for Scientists: A Companion for Students

A work on the best practices in all the major areas of research management and practice that are common to scientific researchers, especially those in academia. Aimed towards the younger scientist, the book critically examines the key areas that continue to plague even experienced and well-meaning science professionals.

Request materials for non-commercial use.

People

Graduate Students


Postdoctoral Associates


Professional Staff


Chandler Brown

Research Technician

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Timothy Chaffin

Research Technician

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Cassie Halvorsen

Administrative Assistant

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Lance Hamilton

Research Technician

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Stacee Harbison

Research Technician

Lana Howe

Research Technician

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Brianna Jacobs

Research Technician

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Mitra Mazarei

Research Scientist

Reggie Millwood

Lab Manager and Research Associate

Bryce Trull

Undergraduate Student Assistant

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Yongil Yang

Research Scientist