First report of the root-lesion nematode Pratylenchus neglectus on wheat in North Dakota

Authors: YAN, GUIPING - North Dakota State University; PLAISANCE, ADDISON - North Dakota State University; HUANG, DANQIONG - North Dakota State University; LIU, ZHAOHUI - North Dakota State University; CHAPARA, VENKATA - North Dakota State University; Handoo, Zafar

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/28/2016
Publication Date: 8/6/2016
Publication URL: http://handle.nal.usda.gov/10113/63183
Citation: Yan, G.P., Plaisance, A., Huang, D., Liu, Z., Chapara, V., Handoo, Z.A. 2016. First report of the root-lesion nematode Pratylenchus neglectus on wheat in North Dakota. Plant Disease. 100(8):1794.

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. Lesion 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 wheat field in Walsh County, ND, a species of lesion nematode called Pratylenchus neglectus by both morphological and molecular means. 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: Root-lesion nematodes (Pratylenchus spp.) are important nematode pests that invade roots of plants and restrict productivity of wheat. In August 2015, a soil sample was collected from a harvested wheat field in Walsh County, ND and was found to contain 1,044 root-lesion nematodes per kg of soil using the sugar centrifugal flotation method. In October 2015, four soil samples were collected from the same field and had root-lesion nematodes ranging from 125 to 1,000/kg soil. One soil sample with 500 lesion nematodes/kg soil was used to inoculate hard red spring wheat cvs. Glenn and Faller. After 10 weeks of growth in a greenhouse room maintained at 22°C, wheat roots were harvested and washed, and light brown lesions were observed on lateral roots. The washed roots were cut into 1-cm segments for nematode extraction using the Whitehead tray method. After 48 hours, lesion nematodes were recovered from the root tissues. Averages of 24 and 20 root-lesion nematodes per gram were found in the roots of Glenn and Faller, respectively. Nematodes from soil and wheat roots were examined morphologically and molecularly for species identification. Morphological measurements of adult females (n = 10) included body length (range = 402.0 to 495.0 µm, mean = 446.0 µm), stylet (15.0 to 17.5, 16.4), tail length (16.0 to 22.0, 18.8), body width (17.0 to 22.0, 19.6), anterior end to basal bulb (90.0 to 115.0, 101.6), a = (21.2 to 24.7, 23.1), b = (3.7 to 4.8, 4.4), c = (19.6 to 27.1, 23.8), and V (81.0 to 85.0%, 82.8%). The lip region had two annules, and was not set off, with anterior margins of apical lip annule convex, second annule was slightly wider than the first; lateral field had four lines with central zone of lateral field having oblique striae; tail terminus was smooth, rounded or slightly oblique. The nematode species was identified as Pratylenchus neglectus based on morphological and morphometric characteristics. DNA was extracted from single nematodes (n = 11) isolated from both soil and wheat roots, and ITS region of rDNA was amplified. PCR products from three nematodes were cloned using pGEM-T easy vector and sequenced, and the resulting ITS sequences were identical. The consensus sequence (GenBank Accession No. KU705392, 684 bp) was 99% homologous with one population of P. neglectus from China(JX046941) and 83% or less identical to other Pratylenchus spp. including P. thornei, a species closely related to P. neglectus. The specific primers from D3 28S rRNA and ITS rDNA were used to amplify DNA of eight nematodes and produced single bands specific for P. neglectus. The combination of the molecular tests confirmed the target species as P. neglectus. Two species of root-lesion nematodes, P. neglectus and P. thornei, were reported as damaging pathogens affecting wheat production in the Pacific Northwest. To our knowledge, this is the first report of P. neglectus on wheat in North Dakota. The resistance levels of various wheat cultivars to this lesion nematode are being identified.