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CORESTA Congress, Edinburgh, 2010, AP 02

The effect of topping on yield, quality and TSNA accumulation in Burley tobacco

JACK A.M.; FISHER C.R.; SCHOERGENDORFER A.; FANNIN F.F.; BUSH L.P.
University of Kentucky, Dept. of Plant & Soil Sciences, Lexington, KY, USA

It is known that lower alkaloids result in lower TSNAs, and that untopped tobacco has lower alkaloids than topped tobacco. The objective of this study was to quantify the effect of not topping on TSNAs, other nitrogenous components, physical characteristics, yield and quality. Experimental design was a split plot, with varieties as main plots and topping treatments as subplots. Varieties were a high converter selection of TN 90 (TN 90H) and commercial low converter TN 90 (TN 90LC). Topping treatments were topped (10% bloom) and untopped (topped one day before harvest). Suckers were controlled with contact suckerides. NNN, NAT, total TSNAs, total alkaloids, nitrite and total nitrogen were lower in the untopped treatment. Marginal means for total TSNAs were 7.1 ppm in the topped treatment and 4.2 ppm in the untopped. The untopped treatment reduced TSNAs from 2.5 ppm to 1.4 ppm in TN 90LC, and from 10.5 ppm to 6.2 ppm in TN 90H. Nicotine to nornicotine conversion was higher in the untopped treatment. There were no differences between topping treatments for nitrate, leaf length and area, leaf number and stalk height. Yield (2515 vs. 2691 kg/ha), grade index (49 vs. 65), crop index and % F grades were lower in the untopped treatment. The low grade index in the untopped tobacco was largely a function of the preponderance of K grades (40% vs. 13%). There were no differences between topping treatments for % tip grades, price, value per ha and quality grades. Not topping almost halved TSNAs, but had a very detrimental effect on the quality of the tobacco, changing it from quality flavor leaf to filler.