Abstract
At present there is no information about the level of genetic variability in N. tabacum and in the Nicotiana genus as revealed by random amplified polymorphic DNA (RAPD). Such knowledge could be useful for taxonomic and breeding purposes. The aim of this paper is to assess the potential application of the DNA polymorphisms generated by RAPD markers within this genus and in tobacco. As rigorously standardized reaction conditions are required to obtain a reproducible RAPD marker, four rapid DNA extraction methods were compared and several parameters of the reaction conditions for the random polymorphic DNA amplification were analysed and optimized. The DNA of six-week-old leaves of N. tabacum var. Samsun was obtained with the following methods differing in the strategy of purification: the cetyltrimethylammonium bromide (CTAB) method, that of Edwards, nucleon phytopure system and the method of Goring. Reproducible amplification profiles were obtained with all the methods except for Edwards'. As regards amplification conditions, the effects of primer-template annealing temperature, of a final extension step, of the number of cycles and of the length of extension time in each cycle were analysed. Moreover, the effects on amplification reaction of the DNA amount, of MgCl2, primer and deoxynucleotide triphosphate (dNTP) concentration were evaluated. Then DNA of 12 Nicotiana species and Nicotianatabacum was amplified with primers OPA-01 and OPA-13 which revealed a considerable polymorphism. The same primers used to analyse 36 var. of N. tabacum belonging to different types, showed identical amplification profiles. Further amplification experiments were carried out with only 12 of the tobacco lines; three primers among the 12 assayed revealed one polymorphic fragment each.