First report of the ring nematode Mesocriconema nebraskense from a corn field in North Dakota

Authors: YAN, GUIPING - North Dakota State University; PLAISANCE, ADDISON - North Dakota State University; HUANG, DANQIONG - North Dakota State University; BAIDOO, RICHARD - North Dakota State University; RANSOM, JOEL - North Dakota State University; Handoo, Zafar

Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/5/2018
Publication Date: 12/3/2018
Citation: Yan, G.P., Plaisance, A., Huang, D., Baidoo, R., Ransom, J.K., Handoo, Z.A. 2018. First report of the ring nematode Mesocriconema nebraskense from a corn field in North Dakota. Journal of Nematology. 50(4):531-532. https://doi.org/10.21307/jofnem-2018-043.
DOI: https://doi.org/10.21307/jofnem-2018-043

Interpretive Summary: Plant-parasitic nematodes are microscopic worms that attack plant roots and cause an estimated ten billion dollars of crop loss each year in the United States and 100 billion dollars globally. Ring nematodes are an important problem damaging the roots of many kinds of plants worldwide. One problem with determining the extent of damage to crop plants is that the nematodes present in many areas are not known, such as in North Dakota. This brief report describes how a team of North Dakota State University and ARS scientists identified from a corn field in Sargent County, ND, a species of ring nematode called Mesocriconema nebraskense by both morphological and molecular means. They also discovered how to distinguish this species from closely related species with molecular and anatomical features. This discovery is significant because it is the first report of this nematode in North Dakota and the molecular information obtained will allow this nematode to be more easily distinguished from closely related species. Therefore, this research will be used by scientists, growers, action agencies, and extension agencies involved in nematode research and control.

Technical Abstract: In May 2016, two soil samples were collected from a corn field in Sargent County, ND from which nematodes were extracted from soil using sieving and decanting followed by a sugar centrifugal flotation method (Jenkins, 1964). Plant-parasitic nematodes were identified to genus based on morphological features and their population densities were quantified. Both samples contained ring nematodes at 85-87 per kg of soil. In September 2017, twelve soil samples were collected from the same field. Four of the samples had ring nematodes ranging from 100 to 900 per kg of soil (Fig. 1). One large, composite sample with 75 ring nematodes per kg of soil obtained after mixing positive and negative soil samples was used to inoculate three corn cultivars DK 43-48-RIB, DKC 43-46 and DKC 44-13 each in four replicates. After 14 weeks of growth at 22°C in a greenhouse room, the average population of ring nematodes increased. The final population density from DK 43-48-RIB, DKC 43-46 and DKC 44-13 was 158 ± 151, 283 ± 154, and 156 ± 140 per kg of soil, respectively. The Reproductive Factor was 2.1, 3.8, and 2.1 for DK 43-48-RIB, DKC 43-46, and DKC 44-13, respectively, indicating that this ring nematode was able to infect and reproduce on these three corn cultivars. Individual ring nematodes were hand-picked from nematode suspensions isolated from field and greenhouse samples and examined morphologically and molecularly for species identification. Morphometric measurements of adult females (n = 10) included body length (mean ± standard deviation = 546.6 ± 64.0 µm, range = 425.0 – 627.0 µm), stylet (56.2 ± 1.6, 54.0 – 60.0), tail length (27.4 ± 3.2, 22.0 – 32.0), maximum body width (50.9 ± 2.5, 49.0 – 55.0), anterior end to basal bulb (124.3 ± 8.8, 110.0 –140.0), a (total body length divided by maximum body diameter: 10.7 ± 1.5, 8.5 – 13.6), b (total body length divided by pharyngeal length: 4.4 ± 0.7, 3.9 – 4.8), c (total body length divided by tail length: 20.0 ± 2.5, 16.1 – 25.0), V (percentage of length from anterior end to vulva position in total body length: 91.7 ± 0.6%, 90.7 – 92.8), R (total body annules:105.0 ± 6.0, 98.0 –118.0), Rex (annules from anterior end to excretory pore: 28.3 ± 1.3, 26.0-32.0), RV (total annules from vulva to tail terminus: 9.0 ± 0.7, 8.0 –10.0), Rvan (total annules from anus to tail terminus: 5.1 ± 0.3, 5.0 – 6.0), body diameter at vulva (39.4 ± 3.0, 33.0 – 40.0), and body diameter at anus (29.5 ± 2.8, 25.0 – 33.0). Lip region having two annules that are smaller and narrower than other body annules but are not set off. Body annules are retrorse with smooth margins, labial disc elevated surrounding the oral opening, stylet robust with well-developed knobs, submedian lobes present, vulva on 8-10th annule and anus on 5-6th annule from posterior end of body, and post-vulval body portion conical to more or less rounded, with single to multiple lobed terminus. The nematode species was identified as Mesocriconema nebraskense Olson et al., 2017 based on morphological and morphometric characteristics (Olson et al. 2017). DNA was extracted from single nematodes (n = 10) from both greenhouse and field samples using the Proteinase K method (Kumari and Subbotin, 2012). Two ribosomal DNA regions and one mitochondrial DNA region were amplified and sequenced for species identification. The ITS region of rDNA was amplified with primers TW81/AB28 (Joyce et al., 1994), D2-D3 region of 28S rRNA gene with primers D2A/D3B (Subbotin et al., 2008), and cytochrome oxidase subunit I (cox1) gene with primers COI-F5/COI-R9 (Powers et al., 2014). PCR products were purified and submitted for sequencing directly. The sequences were deposited into the GenBank database and assigned with accession number MH013430 (762 bp) for the D2-D3 of 28S rRNA gene, MH013431 (798 bp) for the ITS rDNA, and MH023322 (721 bp) for the mitochondrial cox1 gene. The com