Year of Publication

2016

Degree Name

Master of Science (MS)

Document Type

Master's Thesis

College

Agriculture, Food and Environment

Department

Plant and Soil Sciences

First Advisor

Dr. Robert D. Miller

Abstract

CYP82e4, CYP82e5, and CYP82e10 mutant alleles that minimize the conversion of nicotine to nornicotine have been introgressed into numerous existing low converting (LC) burley varieties and parental lines developed by the Kentucky-Tennessee tobacco breeding program. A backcross breeding protocol was utilized, with the objective being the creation of "e3" varieties that differed from their LC counterparts only for nornicotine and nitroso-nornicotine content. Field studies were conducted in Kentucky and Tennessee during the 2013 growing season, with 17 prospective parental lines and 20 prospective commercial varieties grown and compared to their original counterparts. Most of the e3 lines were not morphologically equivalent to their LC counterparts; several were also lacking in black shank resistance. Selections and/or backcrosses to the appropriate LC counterparts were made in 2013 in an attempt to improve the e3 lines to make them more comparable to the LC versions. The improved parental lines and hybrids were re-evaluated in 2014. The comparative performance of e3 versus LC lines was substantially improved in the 2014 trials. After making selections and/or one or two backcrosses, the plant type and black shank resistance were improved for all e3 lines. The reduction in nicotine to nornicotine conversion was successful, with the e3 lines having conversion rates ranging from 0.48 to 0.66 percent, compared to a range of 2.35 to 4.86 percent for the LC lines. With a lower rate of conversion to nornicotine, the nitroso-nornicotine amounts were also reduced; values for the e3 materials ranged from 0.06 to 0.12 ppm, compared to a range of 0.27 to 0.61 ppm for the LC materials. All data for disease resistance, agronomic characteristics, and yield are presented.

Digital Object Identifier (DOI)

https://doi.org/10.13023/ETD.2016.452

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