Building better biofuel crops: A field evaluation of transgenic Populus modified to improve feedstock performance for bioenergy use

Author

Molli Elisabeth Coombs, West Virginia UniversityFollow

Semester

Summer

Date of Graduation

2024

Document Type

Thesis

Degree Type

MS

College

Eberly College of Arts and Sciences

Department

Biology

Committee Chair

Stephen DiFazio

Committee Co-Chair

Jennifer Hawkins

Committee Member

Jennifer Hawkins

Committee Member

Jonathan Cumming

Abstract

A transition away from fossil fuel use is necessary for the future of energy production, and biofuels are a renewable energy option that can mitigate the impacts of fossil fuels through lowered carbon emissions and possible carbon sequestration. In order to successfully compete with fossil fuels, the production of biofuels must be sustainable and cost effective. Populus species are a biofuel crop used for bioenergy conversion from lignocellulosic biomass that have been proposed for use in feedstock plantations on marginal lands, which would avoid competition with agricultural production. Two challenges of feedstock production being faced are recalcitrance to chemical processing, and the effects of increasing stress on plant productivity. To address these challenges, genetic manipulation is being used to improve agronomic performance and achieve desired growth and wood property phenotypes. It is important to understand how these modified feedstocks will perform in plantations to ensure they are achieving desired phenotypes and improving production for biofuel use.

To understand how transgenic Populus feedstocks perform under conditions like proposed plantations I examined two transgenic field trials addressing the challenges mentioned previously. The first study examined Populus deltoides transformed with genes that showed reduced recalcitrance phenotypes in preliminary greenhouse studies. It was observed that the phenotypes exhibited in greenhouse studies were not present under field conditions, and none of the transgenic lines showed improved growth compared to the controls. One transgenic line overexpressing O-acetyltransferase had an increased S/G ratio, a phenotype indicative of reduced recalcitrance, but had decreased growth compared to controls. The loss of phenotypes could possibly be a result of transgene silencing under field conditions or low target gene expression, but RNA analysis is needed to confirm. The second study of this thesis examined the performance of Populus tremula x alba transformed with heat, salt, and water deficit stress response genes to improve stress tolerance. These genes were paired with a constitutive gene promoter and a stress inducible promoter to examine how the inducibility of target gene expression impacts field performance. This study found that there is no clear difference in performance in the field based on promoter type, and the only significant difference in performance compared to controls was observed in Heat shock factor 2 overexpression lines that exhibited impaired growth in the field. Collectively my research shows that the performance of transgenic feedstocks can differ greatly under field conditions compared to greenhouse performance, and that field screenings are crucial in developing transgenic feedstocks for bioenergy use.

Recommended Citation

Coombs, Molli Elisabeth, "Building better biofuel crops: A field evaluation of transgenic Populus modified to improve feedstock performance for bioenergy use" (2024). Graduate Theses, Dissertations, and Problem Reports. 12521.
https://researchrepository.wvu.edu/etd/12521