Agronomic, Chemical, and Smoke Characteristics of Flue-cured Tobacco Lines with Different Levels of Total Alkaloids

Total alkaloids (predominately nicotine) are important constitutents in flue-cured tobacco (Nicotiana tabacum L.). Due to varying nicotine levels in cigarettes, it is of interest to see what effect varying alkaloid levels in tobacco have on certain agronomic and chemical characteristics of the cured leaf. Experiments were conducted at two locations to develop lines of flue-cured tobacco with different levels of total alkaloids and to evaluate these lines for agronomic, chemical, and smoke characteristics. Three flue-cured cultivars with different total alkaloid levels were chosen as recurrent parents. The parents and alkaloid levels were: 'Coker 139' (1.88%), 'NC 95' (3.28%), and 'SC 58' (4.51%). Each cultivar was crossed with a low alkaloid line (0.20%). After the initial cross, backcrosses were made in each F₂ population between a low alkaloid plant and its respective recurrent parent. BC₅F₇ generation plants with different levels of total alkaloids were selected and advanced to the BC₅F₇ to obtain stable lines. Also dihaploids were developed from BC₅F₇ plants and lines with different levels of total alkaloids were selected. Both the BC₅F₇ and dihaploid populations were evaluated. Based on these tests the line with the highest yield and grade index at each alkaloid level was further evaluated for total alkaloids, reducing sugars, yield, grade index, days to flower, plant height, and number of leaves per plant. Lines with the following levels of total alkaloids were evaluated: NC 95 family - 0.34, 1.08, 2.05, 3.11, and 3.55%; SC 58 family - 0.38, 1.59, 1.90, 2.82, 4.18, and 4.82%; and the Coker 139 family - 0.20, 0.93,1.66,1.84, and 2.17%. The 1.08% line in the NC 95 and 1.59% line in the SC 58 families were dihaploids. None of the lines converted appreciable amounts of nicotine to nornicotine. Therefore, the total alkaloid levels reflected predominantly nicotine. In most families the high alkaloid lines gave the highest grade index. Days to flower, plant height, and number of leaves per plant were not associated with total alkaloid levels in cured leaf. Cigarette smoke from the different tobacco lines was evaluated by two smoke panels. The results from Panel A indicated that it was difficult to associate any of the taste parameters with levels of total alkaloids in the leaf. The results from Panel B indicated that an increase in total alkaloids in the leaf was accompanied by an increase in flavor of the smoke.