نوع مقاله : علمی پژوهشی-فارسی
نویسندگان
1 دانشجوی کارشناسی ارشد، گروه گیاه‌پزشکی، دانشکده کشاورزی، دانشگاه شهید چمران اهواز، اهواز، ایران
2 دانشیار، گروه گیاه‌پزشکی، دانشکده کشاورزی، دانشگاه شهید چمران اهواز، اهواز، ایران
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Background and Objectives
Filenchus is one of the most diverse genera of the family Tylenchidae, with various feeding habits. The members of this genus feed on fungi in the soil and the epidermal cells of plant roots. A species belonging to Filenchus was recovered and identified during a survey on the fauna of the plant-parasitic nematodes from the soil around the roots of corn in the north of Khuzestan province (Dezful city). This study aimed to characterize the recovered population based on the morphological and morphometric characters and reconstruct its phylogenetic affinities using 18S rDNA and D2-D3 expansion segments of the 28S rDNA sequences. Additionally, the phylogenetic relationships of the Iranian population with other populations of the species and other species of Filenchus were investigated.
Materials and Methods
Several soil samples were collected around the roots of corn fields in the north of Khuzestan province. The centrifugal-floatation and tray methods were used to extract the nematodes from the soil samples. The collected specimens were fixed, transferred to pure glycerin, and mounted on permanent microscopic slides. The species was recognized using an Olympus CX31 light microscope equipped with a drawing tube based on the morphological and morphometric characteristics, and valid keys. The nematode specimens were photographed using an Olympus BX51 microscope with a Tucsen Michrome 20 digital camera. The morphological and morphometric characters of the population were compared with other reported populations of the species. For molecular analyses, DNA was extracted from the studied nematodes. The DNA samples were stored at –20°C until used as a PCR template. Primers for amplification of 18S rDNA were forward SSUF22 and reverse SSUR13. Primers for D2-D3 expansion segments of the 28S rDNA amplification were forward D2Ab and reverse D3B. The polymerase chain reactions (PCRs) were performed to amplify the abovementioned loci. Amplification success was evaluated with electrophoresis on 1% agarose gel. The PCR products were subjected to sequencing. The newly obtained sequences of the studied species were deposited into the GenBank database (PQ803453-PQ803455). The molecular phylogenetic analyses were performed using a partial sequence of the 18S rDNA and D2-D3 expansion segments of the 28S rDNA based on the Bayesian inference under the GTR + G + I model.
Results
A population of Filenchus was recovered in the present study. The morphological, morphometric, and molecular studies based on the 18S rDNA and D2-D3 expansion segments of the 28S rDNA indicated that the recovered population belongs to F. vulgaris. This population has females with a length of 630 to 722 µm, lateral field with four incisures, and stylet 10.5 to 11.2 µm long. Males were observed in fewer numbers than females, with spicules of 17.0 to 18.5 µm. In the phylogenetic tree inferred using the 18S rDNA sequences, the newly generated sequences of the Iranian population of F. vulgaris formed a clade with other sequences of F. vulgaris and sequences of other species of Filenchus and species of Tylenchus and Neopsilenchus genera. 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 28S rDNA gene. This clade included sequences of other species of Filenchus and species of the two genera Tylenchus and Irantylenchus. The molecular data of the Iranian population of the species were presented for the first time in this study.
Discussion
The identification of most of the species of the genus Filenchus was based only on morphological and morphometric characteristics. Multiple phylogenetic analyses have shown that the genus Filenchus is polyphyletic. In the phylogenetic trees, the sequences of some populations of F. vulgaris are relatively far from each other and even in two different clades. With the increase of sequences of various species of the genus, especially from different populations that belong to different geographical regions, the grouping of populations and species may change, and the phylogenetic relationships between them might be more specific.
کلیدواژه‌ها [English]
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