Abstract
In this survey, 14 populations of Mesocriconema xenoplax were collected from the rhizosphere of eight fruit and nut trees in Fars province, Southern Iran. The phylogenetic relationships of these populations with other representatives of the species were investigated using sequences of cytochrome c oxidase subunit 1 mitochondrial gene (COI) and D2-D3 expansion fragments of 28S rDNA. Phylogenetic studies indicated a close relationship of the currently sequenced populations with known haplotype groups (HG) in the COI tree and revealed two separate lineages in the 28S rDNA tree. Moreover, the genetic diversity of the populations was analyzed using seven ISSR primers as molecular markers. The estimated genetic diversity among populations regarding associated trees and geographic regions were low values of 3.3% and 5.9%, respectively, indicating high gene flow among the recovered nematode populations. On the other hand, the estimated fixation index (F(ST)) was higher for associated plants than for geographic regions (0.611 vs 0.504) indicating that plant-based population segregation better explains genetic diversity in this species. This work expands our knowledge of the genetic structure of this cosmopolitan species of plant-parasitic nematodes.