GENETIC AND EVOLUTIONARY RELATIONSHIP AMONG NICOTIANA SPECIES AS ELUCIDATED BY AFLP

Abstract

Twenty two species representing three subgenera of the genus Nicotiana and two interspecific hybrids were analysed by AFLP. A total of 554 bands were amplified by 6 primer pairs, of which 541 (97.65%) were polymorphic and 13 (2.34%) monomorphic. The primer combination E-AAC/M-CTG gave the highest polymorphic information content (PIC) across all species, whereas E-AAG/M-CAC gave the lowest PIC score. A total of 59 species specific markers were generated, of which 54, 4 and 1 were specific to subgenera Petunioides, Tabacum and Rustica respectively. The pair-wise similarity measure in the species of subgenus Rustica was 0.35 whereas it was 0.29-0.50 in subgenus Tabacum, suggesting that there was significant diversity among the species of these subgenera. In the species of subgenus Petunioides, the range of pair-wise similarity measure was 0.25 to 0.95. The high genetic similarity (95%) was due close relationship among the species belonging to the sections Rependae and Trigonophyllae. Sub-grouping of the species within the main clusters of dendrogram was largely based on the chromosome number. AFLP was found efficient in determining the extent of interspecific genetic diversity existing in genus Nicotiana. The subgenus and species specific AFLP markers identified in this study would be useful in introgression breeding programs of tobacco. N. tabacum shared 174/198 AFLP fragments with the two progenitor species, thus providing molecular evidence that these two wild species contributed genetic information to N. tabacum