The aquarium fish industry has become a capacity for job creation and income
generation. Aquarium fish were used for decoration and are creating tranquility in the
environment and beautification in public places. This study investigated genetic
variation between different populations of various varieties of guppy ornamental
aquarium fish using inter simple sequence repeat (ISSR) markers in Iran for the first
time. DNA was extracted from twelve strains. The polymerase chain reaction was
performed using seven ISSR primers. GenAlex 6.501 and XLSTAT software were used
to analyze data. Results of analysis of molecular variance showed that 54% of observed
polymorphism belongs to variance among populations, and 46% corresponds to
diversity between populations. The highest and the lowest polymorphism percentage
belonged to (GAG)5GC (90%) and (AG)8C (41%) markers, respectively. The percentage
of polymorphic loci ranges from 32.31% to 86.15%. The results of the phylogenetic tree
showed that this tree was divided into two major clusters. Cluster I included only two
populations and cluster II contained the other ten studied populations. It is suggested
that this marker system was efficient in discriminating each genotype at the molecular
level and can be used for genetic diversity analysis for aquarium guppy fish because a
greater understanding of the species' potential is necessary for supporting long-term
genetic improvement.