Microsatellite-based analysis of tobacco (nicotiana tabacum l.) genetic resources
Little is currently known about the genetic variation within diverse gene pools of cultivated tobacco (Nicotiana tabacum L.). Knowledge in this area could aid in future germplasm maintenance activities, provide additional information in the area of N. tabacum population genetics, and assist in selection of materials for breeding or genetic investigations. To this end, 702 N. tabacum accessions from the U.S. Nicotiana Germplasm Collection were genotyped with 70 microsatellite markers. A total of 1031 alleles were detected, with an average of 14.7 alleles per marker. Average gene diversity was quite large (0.7362) and was three times the value for a diverse population of U.S. flue-cured tobacco. Cluster analysis using various distance coefficients generated seven consistent groups. Patterns of geographic-specific clustering were frequent but not universal. An analysis of molecular variance for tobacco collected from Central and South America revealed that 92% of the total genetic variation among samples could be attributed to country-specific subpopulations. There was also a significant level of population subdivision between country-specific subpopulations, however. Tobacco samples collected from Peru had both the largest average gene diversity and the largest mean genetic distance, although N. tabacum collected from Mexico had the greatest allelic richness. Tobacco samples collected from Argentina were the most divergent subpopulation.