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Varietal Response of Burley Tobacco to Stage of Physiological Development when Topped¹

Little is known about the effects of stage of physiological development at which the plants are topped on early vs. late flowering cultivars of burley tobacco (Nicotiana tabacum L.). Four cultivars with a range of 18 days in flowering were topped at different stages of development to determine the optimum topping date for specific cultivats, whether discrimination would exist if all cultivars were topped simultaneously, and whether or not it would be feasible to use an extremely late-flowering cultivar commercially.

Topping ‘MS Burley 37 x LS’ or ‘Burley 37’ earlier than full bloom, ‘Burley 49’ later than 50% bloom, or ‘Burley 64’ later than button stage did not increase yield significantly. Percent total N and percent total alkaloids in leaf from plots of the respective cultivars topped at these stages were within normally accepted ranges. Thus, all entries in a variety trial may be topped at the same time without creating undue bias of the estimates obtained. Maximum performance of Burly 64 was obtained when it was topped in the button stage. This indicates that a late flowering cultivar may be grown commercially if it is topped at an earlier stage of development but about the same date as early flowering cultivars.

Key Words: Flowering • Variety testing • Tobacco production practices • Nicotiana tabacum L.

² Research geneticist, Southern Region, ARS-USDA, Greeneville, TN 37743.