![editseq module of dnastar editseq module of dnastar](https://src.onlinedown.net/d/file/p/2018-05-02/9f6e26cde0bc22b7d9c34973fa7d1faa.png)
(2004b) characterized the rDNA sequences of 18S, 5.8S, 28S, internal transcribed spacer (ITS) 1 and ITS2 regions of Paratrichodorus macrostylus, P. 2010 Kumari and Subbotin 2012 Riga et al. In the past 20 years, a few studies reported the molecular characterization of SRN and genetic variability using ribosomal DNA (rDNA) and other genes ( Blaxter et al. 2015b), limited sequence information is available for the SRN. However, in contrast to other well-studied plant-parasitic nematodes having large sequence databases such as Pratylenchus spp. 2017a, b Kumari and Subbotin 2012 Riga et al. Consequently, molecular approaches for identifying SRN species were developed, such as polymerase chain reaction (PCR) restriction fragment length polymorphism (RFLP), species-specific PCR, real-time PCR, and DNA sequencing ( Boutsika et al.
![editseq module of dnastar editseq module of dnastar](https://res.cloudinary.com/dnastar/image/upload/v1629810758/MAPro-IC4.png)
Even though the identification of nematode species can be accomplished by morphometric measurements ( Decraemer and Baujard 1998), it is often difficult to differentiate closely related species due to limited diagnostic characteristics and minor morphological differences ( Riga et al. Therefore, it is important to identify the SRN species present in crop fields to optimize nematode management strategies. Among them, 13 species transmit plant viruses (mainly Tobacco rattle virus, Pea-early browning virus, and Pepper ringspot virus) and cause severe economic damage on crops ( Decraemer and Robbins 2007). It has been reported that the Trichodorus and Paratrichodorus genera have the largest number of species and are distributed worldwide ( Taylor and Brown 1997). Stubby root nematodes (SRN) belonging to the family Trichodoridae are plant-ectoparasitic and comprise six genera: Trichodorus Cobb, 1913 Paratrichodorus Siddiqi, 1974 Nanidorus Siddiqi, 1974 Monotrichodorus Andrássy, 1976 Allotrichodorus Rodriguez Montessoro, Sher and Siddiqi, 1978 and Ecuadorus Siddiqi, 2002 ( Heydari et al. The intra- and interspecies genetic diversity of rDNA in this study will provide more information for understanding the evolutionary relationships of SRN and will be valuable for future studies of SRN species identification and management. This study documented the occurrence of SRN species across multiple states. allius populations from the same geographic regions. Indel variation of ITS2 rDNA was present in P. Based on phylogenetic analysis, the four SRN species formed a monophyletic group, with P. Both intra- and interspecies variations were higher in ITS rDNA than 18S rDNA and D2-D3 of 28S rDNA. Accordingly, their rDNA sequences were characterized by analyzing D2-D3 of 28S rDNA, 18S rDNA, and internal transcribed spacer (ITS) rDNA obtained in this study and retrieved from GenBank. Sequencing of ribosomal DNA (rDNA) or species-specific polymerase chain reaction assays revealed the presence of four SRN species, including Paratrichodorus allius, P.
![editseq module of dnastar editseq module of dnastar](http://www.achema.sg/pics/1SeqB_circ_seq_thumb.jpg)
SRN were found in 106 soil samples with population densities of 10 to 320 SRN per 200 g of soil and in eight of the nematode suspensions. In 2015 to 2017, 184 soil samples and 16 nematode suspensions from North Dakota, Minnesota, Idaho, Oregon, Washington, South Carolina, North Carolina, and Florida were assayed for the presence of SRN. SRN transmit Tobacco rattle virus, which causes potato corky ringspot disease, thereby having a significant economic impact on the potato industry. Stubby root nematodes (SRN) are important plant parasites infecting many crops and widely distributed in many regions of the United States.