Masters Theses
Date of Award
12-2024
Degree Type
Thesis
Degree Name
Master of Science
Major
Plant Sciences
Major Professor
Charles N. Stewart, Jr.
Committee Members
Gino J. D'Angelo, Sebe A. Brown, Feng Chen
Abstract
As soybean (Glycine max) cultivation expands into new areas, it is exposed to atypical pests like mammalian wildlife. The white-tailed deer (Odocoileus virginianus) is reported to cause the most yield losses out of all wildlife pests, and economic reports reflect that this is a worsening issue. Current crop protection strategies are insufficient and outdated. In plant biotechnology, there are many examples of crop protectants being directly incorporated into the plant using genetic engineering. Such systems have been successful in deterring insect pests, and similar strategies could be employed to mammalian pests. Plant trypsin inhibitors show promise as a potential deterrent based on the established feeding strategies employed by deer. Newly developed lines of transgenic soybean with redirected expression of native trypsin inhibitors showed promise in deterring both insect and deer herbivory without any phenotypic differences from nontransgenic lines. Four lines of transgenic soybean expressing the KTi7 or BBi5 trypsin inhibitor genes under the control of the CaMV 35S or soybean RBCS-SRS4 green tissue promoter were selected for field testing against insects or deer, and the highest expressing line was examined in controlled deer feeding experiments. Two field experiments were designed to quantify transgenic trypsin inhibitor soybean lines’ potential resistance defoliation from insects or deer. One field experiment was dedicated to growth characterization and quantifying herbivory resistance in ambient insect conditions. A separate field experiment was dedicated to quantifying herbivory resistance under ambient deer feeding conditions. Deer preference between transgenic trypsin inhibitor lines and nontransgenic soybean was also quantified in controlled deer feeding experiments in collaboration with the University of Georgia’s Whitehall Deer Research Facility. No significant difference in growth characteristics were found between transgenic trypsin inhibitor lines and nontransgenic soybean grown in field conditions. Two of the four transgenic trypsin inhibitor lines exhibited significantly reduced defoliation compared to nontransgenic soybean in ambient insect herbivory field conditions. In ambient deer herbivory field conditions, there was no difference in defoliation between nontransgenic and transgenic trypsin inhibitor soybean lines. In controlled feeding trials with tame captive deer, there was no significant difference between the amount of transgenic trypsin inhibitor and nontransgenic soybean consumed.
Recommended Citation
Birdwell, Audrey E., "The potential for trypsin inhibitor expression in leaves to convey herbivory deterrence in soybean. " Master's Thesis, University of Tennessee, 2024.
https://trace.tennessee.edu/utk_gradthes/12839
