The contributions of genetic diversity to the performance of sun-cured tobacco

Genetic diversity is a fundamental component in improving yield potential, quality, and adaptability in economically important crops such as tobacco (Nicotiana tabacum L.). Turkish sun-cured tobaccos, renowned worldwide for their distinctive aromatic profiles, are cultivated across diverse agroecological regions of Türkiye using genetically heterogeneous local genotypes. This study aimed to characterize the genetic diversity among Turkish sun-cured tobacco landraces using SSR markers and to elucidate its association on agronomic and chemical traits across major production regions. For this purpose, a total of 331 genotypes were collected from three major tobacco-growing regions. To assess genetic diversity at the DNA level, molecular characterization of the genotypes was conducted using nine SSR markers. All SSR markers were polymorphic and generated between 3 and 6 alleles per locus. Among the 331 genotypes analyzed, 259 were identified as genetically unique, including 146 from İzmir, 71 from Samsun, and 42 from Tokat. A dendrogram constructed from the SSR data revealed that most genotypes clustered according to their respective tobacco production regions. Distinct regional variations were observed among the studied materials; specifically, Izmir genotypes excelled in reducing sugar content, Samsun genotypes in dry leaf yield and nicotine levels, and Basma genotypes in both dry leaf yield and reducing sugar accumulation. Based on dry leaf yield and regional adaptation traits, 19% of the İzmir genotypes, 24% of the Samsun genotypes, and 18% of the Tokat genotypes outperformed the commonly cultivated commercial varieties in their respective regions. The pronounced regional differences in sun-cured tobacco quality largely stem from unique landraces, each genetically adapted and named after their region of origin. These findings show the fundamental role of genetic diversity in sustaining and enhancing sun-cured tobacco production and affirm its contribution to the continued cultivation of distinctive Turkish oriental tobaccos.