N-nitrosonornicotine reduction in dark tobacco varieties and smokeless product prototypes
During the past decades there has been a substantial effort to reduce the level of the tobacco specific nitrosamine N-nitrosonornicotine (NNN) and its precursor nornicotine in tobacco and tobacco products. Research on the mechanism of nornicotine formation led to the identification of three tobacco genes (CYP82E4, CYP82E5 and CYP82E10) encoding for cytochrome P450 nicotine demethylases that convert nicotine to nornicotine. Through conventional breeding, we developed dark tobacco (stable reduced converter/SRC) varieties containing the three non-functional nicotine demethylase genes. Tobacco varieties containing this new technology, named ZYVERT™, were grown on on-farm experiments and, leaf produced from these varieties, were used to make smokeless product prototypes. Control product prototypes were produced using leaf from commercial low converter (LC) varieties. Our results indicate that the presence of non-functional alleles of the three genes reduces the level of nornicotine and NNN in dark tobacco varieties by about 70 % compared to the level observed in commercial LC dark tobacco varieties. The reduced levels of NNN in the cured leaf of SRC varieties were also observed in smokeless product prototypes.