Altering Condensate Levels in Tobacco Smoke by Genetic Techniques

Condensate deliveries from cigarettes can be reduced by manufacturers in various ways. Lines or cultivars of tobacco can also be developed whose cured leaf, upon pyrolysis, delivers less condensate in the smoke. Since there appears to be an association between condensate and nicotine in smoke, the condensate : nicotine ratio is important to the development of lines of tobacco that deliver low condensate levels. Experiments were conducted to evaluate the potential for genetically controlling condensate delivery in cigarette smoke and data are presented. In general, when comparing the condensate delivery potential for different classes of tobacco, Burley delivered higher condensate values followed by dark fire-cured, dark air-cured, flue-cured and Maryland cultivars. In selecting genotypes for lowering condensate deliveries, the condensate / g of tobacco smoked is a better index than condensate/cigarette. In evaluating low-alkaloid tobaccos, the condensate delivery did not decrease appreciably as the total alkaloids were decreased. On an average, the decrease was about 4 mg of condensate / cigarette when compared with normal-alkaloid types but the condensate : nicotine ratio increased greatly. The ratio of condensate : nicotine was lowered when lines high in nicotine were produced. In one test reported, the ratio of condensate : nicotine ranged from 5.3 (TI 717) to 75.0 for a low-nicotine line. N. rustica had higher nicotine than N. tabacum cultivars and a lower condensate : nicotine ratio. The gene(s) responsible for the production of nicotine in N. rustica were transferred into N. tabacum and some of the derived lines had a nicotine content about 1 % higher than SC 58, the highest-nicotine cultivar, or flue-cured tobacco available. The condensate delivery / g of tobacco smoked was lower for these lines when compared with SC 58. All of the lines tested gave a condensate : nicotine ratio lower than SC 58. The data showed that condensate deliveries from tobaccos vary with the environment, cultural practices and the weather conditions under which the tobacco is produced. To make progress in breeding for lower condensate delivery in tobacco, it is necessary to assay large numbers of samples and methods for doing this were discussed. To breed low-condensate delivery lines with good smoking flavour, it will be necessary, simultaneously, to select for certain flavour compounds. More research is needed on flavour chemicals of tobacco and their relationship to condensate.