Molecular analysis of olive (Olea europaea L.) in Iraq using the internal transcribed spacer (ITS) region

Olea is a genus of about 40 species in the Oleaceae family distributed in warm temperate and tropical areas of southern Europe, Africa, southern Asia, and Australia. The study aimed to use the variations in the Internal Transcribed Spacer 1 (ITS1) region to construct a phylogenetic tree for 12 Iraqi olive varieties with 15 ITS1 sequences downloaded from the NCBI database. Leaf samples were collected from 12 olive varieties grown in five geographical regions of the north of Iraq. Using the BLAST algorithm, 12 sequences were manually adjusted by chromatogram comparison and aligned with the NCBI GenBank database. Haplotype diversity ranged from zero in the Australian population to one in the Moroccan and Spanish populations. Nucleotide diversity ranged from 0.0 in the Australian population to 0.08 in the Algerian population and Tajima's D value was -0.940. Genetic differentiation values ranged from 0.0177 between Iraqi Moroccan and Iraqi Spanish populations to 0.6540 between Iraqi and Algerian populations. The average pairwise nucleotide diversity within populations was 0.9036 in Iraqi and Turkish olive populations to 0.8671 in Iraqi and Algerian populations. The phylogenetic tree formed 2 main clusters. The first cluster includes all Algerian varieties and the Iraqi varieties are grouped in second cluster. The negative Tajima test value in all populations indicates an excess of rare alleles. The high value of gene flow between the Iraqi and Australian populations may have been mediated by human transport and these varieties may have been originated from the same geographical region.