Genetic diversity among flue-cured tobacco (Nicotiana tabacum L.) revealed by amplified fragment length polymorphism

Flue-cured tobacco (Nicotiana tabacum L.) is one of the most important commercial crops in the world. Genetic diversity studies provide estimates on the level of genetic variation among diverse materials that can be used in germplasm management, varietal protection, and flue-cured tobacco improvement. Amplified fragment length polymorphism (AFLP) analysis of 51 flue-cured tobacco cultivars produced a total of 1479 unambiguous DNA fragments. Cluster analyses using the unweighted pair group method with arithmetic mean (UPGMA) showed that the cultivars could be grouped into American or Chinese types, with the Chinese types being further clustered into four subgroups and American ones into two subgroups. The average pairwise genetic distance was 0.167 and ranged from 0.024 to 0.267. AMOVA analysis showed that 55.76% of genetic variation came from cultivars having different origins and 44.24% from cultivars having the same origin. The overall average Fst of the 51 accessions was 0.177. Mean Fst of each accession against the rest ranged from 0.152 to 0.238. The findings of this study revealed that the present day commonly grown flue-cured tobacco germplasm has narrow genetic diversity among the cultivars, necessitating a sustained effort to preserve flue-cured tobacco germplasm resources. Further crosses should be made only with genetically distant varieties.