Aim and Background. Cotton is considered as one of the most important crop plants in Iran, cultivated in various regions of the country. Continuous cultivation of the same genotypes may bring about genetic erosion in the long term therefore study of the available genetic variability as well as introducing the new ones is of importance.

Materials and Methods. Molecular study was performed in 10 tetraploid cotton cultivars (Gossypium

hirsutum L.S). Random Amplified Polymorphic DNA (RAPD) profiles for ten cotton genotypes were

generated with 30 random primers.

Results. Out of 30 primers used 22 primers produced reproducible bands. The primers generated 387 RAPD loci, of which 178 were polymorphic. The primer OPM11 produced the highest number of Polymorphic bands and Primer OPC90 produced the highest number of unique bands while some of the primers produced no unique band at all. Siokra cultivar produced the highest unique bands (6).

Conclusions. NJ clustering methods performed on molecular data. Two parental cultivars of Nazilli and Siokra are grouped together with 100% bootstrap value in NJ dendrogram.