Genetic polymorphism of Indian tobacco types as revealed by amplified fragment length polymorphism

During the past five decades, a large number of tobacco varieties have been developed for different end uses in India through pure line selection from local land-races, mutation breeding and hybridization involving local selections and exotic introductions followed by pedigree selection. No systematic effort has been made to understand the existing diversity pattern in these varieties, which is crucial to define future breeding strategy in this important commercial crop. Amplified fragment length polymorphism (AFLP) analysis was used to determine genetic variation in 54 varieties of cultivated tobacco (Nicotiana tabacum and N. rustica) and three accessions of exotic germplasm. Nine oli-gonucleotide primer-pair combinations resolved a total of 967 AFLP fragments, of which 785 (81.2%) were polymorphic. The mean genetic distance among the 49 cultivars and three exotic accessions of N. tabacum was 15.35%; 22% among the five cultivars of rustica. Genetic polymorphism present among the cultivars of tobacco was low, as evidenced by the high degree of similarity in the AFLP profiles of different tobacco types. All the five cultivars of N. rustica can be readily identified using the primer pairs E-ACT/M-CAG and E-AAC/M-CTG. Two major clusters were formed on the basis of species and seven sub-clusters were formed on the basis of manufacturing quality traits in the cultivars of N. tabacum. Cultivated flue-cured varieties were clustered separately from other air cured types. Species-specific markers identified in this study would be useful in identification of the true hybrids and monitoring introgression of useful genes from the wild relatives. The markers found specific to the varieties can be used in correct identification of the carrier genotypes in trade and commerce.