The principal objectives in breeding tobacco are yield, field and handling characteristics, disease resistance, and quality. Of these objectives, major emphasis has been placed on breeding disease-resistant varieties. Resistant varieties have provided one of the most effective means of combating many of the pathogens that attack the tobacco plant. However, the transfer of genes for disease resistance into susceptible varieties has been accompanied in many cases by other characteristics which are undesirable. It is often a difficult task to combine acceptable type, yield, and quality with desired factors for disease resistance into a single variety.
Legg, Paul D., "Breeding Tobacco Varieties" (1967). Agronomy Notes. 221.