CYP82e4, CYP82e5, and CYP82e10 alleles that minimize the conversion of nicotine to nornicotine have been introgressed into numerous burley tobacco (Nicotiana tabacum L) varieties and parental lines developed by the Kentucky-Tennessee Tobacco Improvement Initiative (KTTII). A backcross breeding protocol was utilized, with the objective being the creation of "e3" varieties that differ only for nornicotine and nitroso-nornicotine content in comparison to the original low converter (LC) varieties. Field studies were conducted in Kentucky and Tennessee during the 2013 growing season where multiple iterations of seven KTTII parental lines, and four iterations of five hybrid commercial KTTII varieties, were grown and compared to their original LC counterparts. Considerable variation for agronomic and/or race 1 black shank resistance was detected among the iterations within specific breeding line and hybrid families. After selection and/or additional backcrosses within parental line families during 2013, e3 parental lines and varieties were again compared with their LC counterparts in 2014 field trials. Much less variation was detected between the e3 and LC versions of breeding lines and varieties in the 2014 field trials. The e3 alleles proved to be very effective in reducing the conversion of nicotine to nornicotine, resulting in a reduction in the formation of nornicotine, and the concomitant formation of nitroso-nornicotine, by approximately 85-90%. As a result of this project, e3 versions of TN 86, KT 209, KT 210, and KT 212 were released as commercial varieties in March, 2015, and it is anticipated that e3 versions of TN 90, KT 204, and KT 206 will be released in March, 2016. (Reprinted with permission)