Genotypic Response of Burley Tobacco (Nicotiana tabacum L.) to Air-curing Detached Leaves

Burley tobacco (Nicotiana tabacum L.) production still requires about 340 hours of labor per acre. Harvesting, barning, and preparing the leaf for market have about as intense labor requirements as 30 years ago. These operations must be mechanized to some degree to maintain production. The major objective of this study was to determine if there is a differential response of diverse hurley genotypes when the leaf is cured detached from the stalk, with a view to producing cultivars whose mechanically-harvested leaf possesses the normal characteristics of burley tobacco. Ten hurley tobacco cultivars and breeding lines that differed from each other in plant type were grown in a split-plot design with genotypes as whole plots and methods of curing as subplots. The methods of curing consisted of conventional air-curing on the stalk and aircuring leaves that had been detached from the stalk and strung on sticks. Yield and grade index were determined for the cured leaf of each treatment. The leaf web was sampled and analyses for percent total nitrogen, percent α-amino nitrogen, water-soluble acids, pH, percent ash, percent K₂0, percent nicotine, percent nornicotine, and content of citric and malic acids were made. Yield, pH, water soluble acids, percent total nitrogen, and percent α-amino nitrogen were higher for detached than for stalk-cured leaves. No significant differences existed between curing methods for percent K₂0, percent nicotine, or percent nornicotine. Leaves cured detached were lower in percent ash and in grade index than those cured conventionally. Certain genotypes, such as Va 509, produced much more acceptable tobacco from the standpoint of both visual and chemical characteristics than others when the leaves were cured detached. Progress may be expected in breeding for cultivars that produce hurley tobacco that is acceptable when it is cured detached from the stalk.