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Divergent Mass Selection for Carotenoids in a Flue-Cured Tobacco Populations¹

Leaf carotenoids are important precursors of aroma and flavor constituents in tobacco, Nicotiana tabacum L. In an F₂ population resulting from a cross of ‘Hicks’ x ‘Coker 139’, five cycles of mass selection were practiced for high and low total carotenoid concentrations in cured leaf. All 10 selected cycle populations, the original F~ population, and parental cultivars were evaluated at two locations. The effectiveness of mass selection for changing total carotenoids, the divergence and asymmetry of responses between the high and low populations and the correlated changes in other characters were measured. Based on a linear concurrent regression model, response to divergent mass selection for total carotenoids was significant in both directions. Average change per cycle of selection for total carotenoids was 4 µg g^-1 for the high population, and —5.4 µg g^-1 for the low population. Progress in the two populations was symmetric with the high population possessing 41% more carotenoids than the low population after five cycles of selection. Important correlated responses in other constituents occurred as well. Total alkaloids were positively correlated with carotenoid changes, diverging 46% between the high and low populations. Total alkaloids were altered 0.17 and —0.13% per cycle for the high and low populations, respectively. Leaf yields and grade index were negatively related to direction of carotenoid selections and diverged at cycle five by 20 and 45%, respectively. The complexity of cured leaf quality determination in tobacco is apparent from this study. If carotenoid concentrations in cured leaf are to be used as an indirect selection criterion for altering aroma and flavor of tobacco, selection schemes to minimize correlated responses for other chemical constituents may be necessary.

Key Words: Nicotina tabacum L. • Recurrent selection • Selection response • Correlated response • Alkaloids

² Former graduate assistant (present address: DSIR, Motueka, New Zealand), and professors of crop science, respectively, North Carolina State Univ., Raleigh, N.C.

Received for publication November 29, 1982.