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First Report of Peanut mottle virus in Forage Peanut (Arachis glabrata) in North America

Rhizoma peanut (Arachis glabrata Benth.) is a forage crop with increasing acreage (>10,500 ha) in the coastal plain region of the United States. Peanut mottle virus (PeMoV), a member of the family Potyviridae, is transmitted nonpersistently by aphids and seed-transmitted in A. hypogaea. Important hosts of the virus include peanut, soybean, and pea. During January of 2006 in Tifton, GA, immature rhizoma peanut plants identifier A176 with a lost PI number and PI 243334 exhibiting chlorotic ringspots were tested for viruses (potyviruses, Tomato spotted wilt virus [TSWV] and Cucumber mosaic virus [CMV]) frequently found in crops in the southeastern United States. All symptomatic plants tested were positive in the general potyvirus screen by indirect ELISA (Agdia, Inc., Elkhart, IN) and negative for TSWV and CMV. Leaves from two symptomatic plants of A176 and several asymptomatic genotypes were blotted onto FTA cards (Whatman Inc., Maidstone, UK) to bind viral RNA for preservation and processed according to the manufacturer's protocol. To determine the specific potyvirus identity, punch-outs from the FTA cards were used for reverse transcription (RT)-PCR (3) to test for PeMoV and Peanut stripe virus (PStV), both of which are found in A. hypogaea in Georgia. The forward primer (5′-GCTGTGAATTGTTGTTGAGAA-3′) and the reverse primer (5′-ACAATGATGAAGTTCGTTAC-3′) were specific for PeMoV and the forward primer (5′-GCACACACTTCTTGGC ATGG-3′) and reverse primer (5′-GCATGCCCTCGCCATTGCAA-3′) were specific for PStV (2). The primers are specific to the respective viral coat protein genes. Amplicons of the expected size (327 bp) were produced from symptomatic A176 and PI 243334 samples but not from the asymptomatic genotypes. The resulting PCR product was sequenced and a BLAST search in GenBank confirmed PeMoV (98 to 99% nt identity with Accession Nos. X73422 and AF023848). This finding is of significance because rhizoma peanuts are typically propagated by cuttings. Therefore, maintaining virus-free stock is critical. Although, PeMoV has been found in A. pintoi in Colombia (1), to our knowledge, this is the first report of PeMoV in rhizoma peanut (A. glabrata) peanut anywhere in the world.

References: (1) A. A. Brandt et al. Plant Viruses Online: Descriptions and Lists from the VIDE Database, 2007. (2) R. G. Dietzgen et al. Plant Dis. 85:989, 2001. (3) R. D. Gitaitis et al. Phytopathology (Abstr.) 95(Suppl):S35, 2005.