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Title: First report of the root-lesion nematode, Pratylenchus scribneri, infecting potato in North Dakota

item YAN, GUIPING - North Dakota State University
item PLAISANCE, ADDISON - North Dakota State University
item HUANG, DANQIONG - North Dakota State University
item Handoo, Zafar
item GUDMESTAD, NEIL - North Dakota State University

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2015
Publication Date: 4/8/2016
Citation: Yan, G.P., Plaisance, A., Huang, D., Handoo, Z.A., Gudmestad, N.C. 2016. First report of the root-lesion nematode, Pratylenchus scribneri, infecting potato in North Dakota. Plant Disease. 100(5):1023.

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 potato field near Cogswell (Sargent County), ND, a species of lesion nematode called Pratylenchus scribneri 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 the most common nematode pests of potato. Five soil samples were collected from a harvested potato field near Cogswell (Sargent County), ND in October 2014 to investigate the occurrence of root-lesion nematodes. Plant-parasitic nematodes were extracted, revealing all the samples contained root-lesion nematodes with several other nematodes. Population densities of the lesion nematodes were 125 to 1,628 (average 791) per kg of soil. In April 2015, the field was resampled and one soil sample with 1,540 lesion nematodes/kg soil was used to inoculate potato cultivar All Blue. After ten weeks of growth in a greenhouse room maintained at 22 °C, the lesion nematode population was found to have increased substantially. The final population density in soil from four replicates averaged 9,163 lesion nematodes/kg soil. Potato roots were washed and brown lesions were observed on lateral roots. The clean 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 with a mean of 48 nematodes/g of roots, indicating this lesion nematode parasitizes this potato cultivar. Nematodes from soil and potato roots were examined morphologically and molecularly for species identification. Morphological measurements of adult females (n = 10) included body length (range = 407.0 to 532.0 µm, mean = 476.5 µm), stylet (15.0 to 15.5, 15.0), tail (25.0 to 28.0, 25.6), body width (21.1 to 28.0, 23.5), anterior end to basal bulb (98.0 to 107.0, 101.4), a (17.7 to 24.6, 20.4 µm), b (4.0 to 5.2, 4.6), c (16.2 to 22.4, 18.5), and V (75.5 to 78.7%, 77.2%). The lip region had two annules. The post-uterine sac in females was approximately 23 µm long, equal to the width of the nematode at the vulva. The morphology and morphometrics of this population are coincident with the original description and redescription of P. scribneri. Molecular analysis of 28S rRNA and internal transcribed spacer of rDNA confirmed the identity as P. scribneri. DNA was extracted from single nematodes (n = 9) isolated from soil and potato roots in 20 'l of worm lysis buffer. The 28S D2/D3 region and ITS region were amplified with primers D2A/D3B and 18S/26S, respectively, and then cloned and sequenced. Sequence (GenBank Accession No. KT873859, 785 bp) from the 28S rRNA was 100% identical to one population of P. scribneri (JX047001, 785 bp) from China and one (EU130864, 760 bp) from California. Sequence (KT873860, 1103 bp) from the ITS rDNA was 98% homologous with four populations of P. scribneri from China (JX046934, 957 bp; JX046932, 889 bp; JX046933, 893 bp; KP995312, 825 bp). To our knowledge, this is the first report of P. scribneri infecting potato in North Dakota. Several Pratylenchus species including P. scribneri are detrimental to potato. The resistance and susceptibility of various potato cultivars to this lesion nematode are being identified.