تعیین مشخصات ریخت‌شناسی و مولکولی گونه pratylenchus mediterraneus corbett, 1983 (tylenchomorpha: pratylenchidae) از ایران

در این مطالعه، جمعیتی از جنس pratylenchus در ارتباط با درختان گز از منطقه حفاظت شده کرخه بدست آمد. مطالعات ریخت‌شناسی، ریخت‌سنجی و مولکولی این جمعیت بر اساس توالی دو ناحیه d2d3 از ژن 28s rrna و ژن its rrna نشان داد این جمعیت متعلق به گونهp. mediterraneus  می‌‌باشد. این جمعیت دارای ماده‌هایی به طول 431 تا 551 میکرومتر با کیسه ذخیره اسپرم پُر و استایلت به طول 15 تا 16.5 میکرومتر می‌باشد. نرهای جمعیت به دست آمده فعال بوده و دارای بدن به طول 331 تا 485، استایلت به طول 14.8 تا 15 و اسپیکول به طول 16.2 تا 19 میکرومتر می‌‌باشند. در آنالیز فیلوژنی با استفاده از توالی‌های ناحیه d2d3 ژن 28s rrna، توالی‌ جمعیت ایرانی به همراه توالی‌های دیگری از گونه p. mediterraneus و تعدادی از توالی‌هایی که به گونه p. thornei  تخصیص داده شده‌اند، در یک کلاد قرار گرفتند. این کلاد در ارتباط خویشاوندی نزدیک با کلادی است که توالی ‌های متعددی از گونه p. thornei را در بر‌گرفته است. در آنالیز فیلوژنی با استفاده از توالی ‌های ژن its rrna، توالی‌ جمعیت ایرانی به همراه توالی‌های دیگری از گونه p. mediterraneus در یک کلاد قرار گرفتند. این کلاد در ارتباط خویشاوندی نزدیک با کلادی است که توالی‌های متعددی از گونه p. thornei را در بر‌گرفته است. ویژگی‎‌های ریخت‌شناسی، ریخت‌سنجی و توصیف جمعیت ایرانی این گونه در تحقیق حاضر برای اولین بار ارائه گردید.

Morphological and molecular characterization of Pratylenchus mediterraneus Corbett, 1983 (Tylenchomorpha: Pratylenchidae) from Iran

Background and ObjectivesThe Karkheh protected area is considered as one of the protected areas of Iran, which harbors a remarkable diversity of vegetation. A population belonging to the genus Pratylenchus was recovered and identified as P. mediterraneus during a survey on the biodiversity of the plantparasitic nematodes in this region of Khuzestan province. This study aims to characterize the population based on the morphological and morphometric characteristics and evaluate its phylogenetic affinities using LSU D2D3 and ITS rDNA sequences. Moreover, its phylogenetic relationships were investigated with other relevant genera and species.Materials and MethodsSeveral soil samples were collected from the rhizosphere of tamarisk trees in Karkheh protected area. The centrifugalfloatation and tray methods were used for extracting the nematodes from the soil samples. The collected specimens were fixed and transferred to the pure glycerin after extracting the nematodes by using the modified De Grisse method. Then, permanent microscopic slides were prepared from the processed nematodes. The species was identified by using a light microscope equipped with a drawing tube based on the morphological and morphometric characteristics, and valid keys. The molecular phylogenetic analyses were performed by using partial sequences of the D2D3 expansion segments of  the large subunit, and internal transcribed spacer (LSU D2D3 and ITS rDNA) regions based on the Bayesian inference under the GTR + G + I model.ResultsA population of the genus Pratylenchus was recovered in the present study. The morphological, morphometric and molecular studies based on the D2D3 domains of the 28S and ITS rRNA gene indicated that the recovered population belongs to P. mediterraneus. The morphological, morphometric, and molecular data of the Iranian population of the species were presented for the first time in this study. In the phylogenetic tree inferred using the 28S rRNA gene sequences, the newly generated sequence of the Iranian population of P. mediterraneus formed a clade with other sequences of the species, and some sequences assigned to P. thornei. All other sequences of P. thornei occupied a clade, in close phylogenetic relationship with the aforementioned clade. The newly generated sequence of the Iranian population formed a maximally supported clade with other sequences of the species in the phylogenetic tree inferred using the ITS rRNA gene.  DiscussionThe two species P. thornei and P. mediterraneus are morphologically very similar and can mainly be separated from each other by presence/absence of male and a functional spermatheca. Their separation is further corroborated by using the partial sequences of 28S and ITS rDNA. The sequences of the two species form the separate clades, and the identification of some sequences occupying the same clade with the sequences of P. mediterraneus need further validations in lack of the morphological data.