An overview of tobacco breeding - Past, present and future

TOBACCO, Nicotiana tabacum L., AROSE FROM the hybridization of two diploid species, N. sylvestris and N. tomentosiformis. This mode of origin and genetic similarities between the two parental species resulted in a high level of genetic redundancy within the tobacco genome. Many simply-inherited traits of economic importance, the burley character for example, are under the control of duplicate genetic loci. Tobacco evolved under a highly self-pollinated reproductive mode, and primitive plant populations would have been composed of heterogenous mixtures of highly homozygous individuals. Selection of unique genotypes within a broad germplasm pool was largely responsible for the differentiation of tobacco into classes or types long before science-based tobacco breeding began. Principal objectives of early tobacco breeding programs were resistance to diseases, along with improvements in yields and physical aspects of cured leaf. Little attention was devoted to chemical composition of cured leaf, and by the 1950s, selection of high yielding cultivars had reduced nicotine in American flue-cured leaf to unacceptable levels. Minimum standards programs for ensuring the quality of American tobaccos were implemented to solve this problem. Tobacco breeding procedures evolve continuously; biotechnology has shortened cultivar development time, provided laboratory methods for gene identification, and permitted introduction and expression of alien genes in the plant. Breeding progress resulting from the use of these technologies and the acceptance of the products by consumers will be discussed.