Location: Nematology LaboratoryTitle: First report of Xiphinema rivesi (Nematoda, Longidoridae) in Washington State) Author
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2013
Publication Date: 11/13/2013
Publication URL: http://handle.nal.usda.gov/10113/59069
Citation: Akinbad, S.A., Mojtahedi, H., Guerra, L., Eastwell, K.C., Villamor, D.E., Handoo, Z.A., Skantar, A.M. 2013. First report of Xiphinema rivesi (Nematoda, Longidoridae) in Washington State. Plant Disease. 91(7):770. DOI: 10.1094/PDIS-09-13-0961-PDN. Interpretive Summary: Plant-parasitic nematodes are microscopic worms that feed on plants and cause an estimated ten billion dollars of crop losses each year in the United States and 100 billion dollars globally. One problem with determining the extent of nematode damage to crop plants is that the nematodes present in many areas are not known. In this study, a team of researchers from the Washington State Department of Agriculture, Washington State University and ARS surveyed and identified the nematodes in cherry orchards in Chelan County, Washington. This research revealed the presence of one of the most economically important nematodes worldwide called the dagger nematode, specifically a species known to transmit disease-causing viruses from one plant to another. The results are significant because this is the first detection of this virus-transmitting nematode in Washington. This research will be of use to scientists, growers, action agencies and others involved in nematode research and control.
Technical Abstract: The dagger nematode Xiphinema rivesi Dalmasso 1969 transmits several viruses in North America and Europe (2), causing severe yield reduction in crops. During a routine survey of cherry orchards suffering from cherry rasp leaf disease caused by Cherry rasp leaf virus (CRLV) (genus Cheravirus) in Chelan County, Washington State, soil samples were collected in March 2013 and transported to the WSDA nematology laboratory in Prosser, WA. About 250 cc soil samples were processed using the centrifugal flotation method (1). Female dagger nematodes were hand-picked, transferred to 0.1% sodium chloride, and sent for morphological and molecular identification to the USDA-ARS Nematology Laboratory in Beltsville, where their identity was established as Xiphinema rivesi Dalmasso, 1969 (4). Morphological characters used for identification included female body, and total stylet (odontostyle and odontophore) length, location of guiding ring from oral aperture, shape of head and tail including various tail measurements, and vulva percentage in relation to body length. Measurements of females (n =10) include body length (range = 1,832-2,203 micrometers, mean = 1,902, standard deviation (SD) = 162.4), odontostyle (80-90, 83, 3.5), odontophore (50-65, 54.8, 4.2), total stylet (130-145, 137.8, 4.2), guiding ring from oral aperture (60-75, 70, 5.1), tail (27.5-35.0, 30.8, 2.5), body diameter at anus (22-28, 24.7, 1.7), J (5.0-7.5, 6.0, 0.9), body diameter at beginning of J (7.5-10.5, 8.5, 1.0), body diameter at 5 um from tail terminus (7.0-8.0, 7.5, 0.2), and V% (49.4-55.0, 52.2, 1.8). Molecular diagnosis as X. rivesi was confirmed after DNA was extracted from two individual nematodes and the templates were used in PCR analysis. The 28S large ribosomal D2-D3 expansion segment was amplified with primers D2A and D3B, and the internal transcribed spacer (ITS) region was amplified with primers TW81 and AB28, as previously described (3). To verify the identity of the sequences generated from PCR, they were subjected to a database search using BLAST (National Center for Biotechnology Information). 28S sequences from this study were >99% identical to several sequences of X. rivesi sampled from Spain (GenBank numbers: JQ990038, JQ990039, HM921357, HM921358). To the best of our knowledge, this is the first time that this nematode is being reported from the State of Washington. The quick and persistent spread of CRLV in most of the orchards visited calls for concern.