October 29, 2004
From: ProMED-mail<promed@promedmail.org>
Source: American Phytopathological Society, Plant Disease Notes [edited]

First report of soybean dwarf virus on soybean in Wisconsin
A. Phibbs and A. Barta, Wisconsin Department of Agriculture, Trade and Consumer Protection, 4702 University Ave, Madison 53707; and L. L. Domier, USDA-ARS, University of Illinois, Urbana 61801. Plant Dis. 88:1285, 2004; published on-line as D-2004-0908-01N, 2004. Accepted for publication 19 Aug 2004.

Soybean dwarf virus (SbDV) causes widespread economic losses on soybean (_Glycine max_ (L.) Merr.) in Japan (4), and has been reported on soybean in Virginia (2), in various legumes in the southeastern United States (1),
and in peas in California (3).

During late July and early August of 2003, soybean plants in Wisconsin were surveyed for SbDV. In 286 soybean fields at the R2-R4 growth stage, the uppermost fully unfurled leaf was collected from 10 plants at each of 5
sites. Samples were collected at random without regard to symptoms. SbDV symptom information was not recorded. Samples were stored on ice until frozen at -80 deg C.

5 fields in 4 Wisconsin counties (Columbia, Lafayette, Sauk, and Waushara) tested positive for SbDV using double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). DAS-ELISA testing was conducted with reagents from Agdia, Inc (Elkhart, IN) following the manufacturer's protocol. Absorbance was read at 405 nm with a Stat Fax 2100 microplate reader (Awareness Technology, Inc., Palm City, FL) or visually evaluated.
DAS-ELISA did not discriminate between strains of SbDV.

The presence of SbDV was confirmed, and strain identity was inferred as dwarfing strain using reverse transcription-polymerase chain reaction (RT-PCR). Total RNA was extracted from homogenized leaf tissue, reverse transcribed, and amplified with the SuperScript One Step RT-PCR System (Invitrogen, Carlsbad, CA) and SbDV-specific primers (5(prime)-CTGCTTCTGGTGATTACACTGCCG-3(prime) and 5(prime)-GCTTTCATTTAACGYCATCAAAGGG-3(prime)). Size of the RT-PCR products (110 bp) was consistent with the
dwarfing strain, SbDV-D.

All locations that tested positive for SbDV showed soybean aphids, _Aphis glycines_ Matsumura (_Homoptera_: _Aphididae_), on 100 percent of soybean plants. Several aphid species have been reported to vector SbDV, but at
this time, vector relations in the Wisconsin infections are unknown.

To our knowledge, this is the 1st report of SbDV infecting soybean in Wisconsin.

References:
(1) V. D. Damsteegt et al. Plant Dis. 79:48, 1995.
(2) A. Fayad et al. Phytopathology (Abstr.) 90(Suppl.):S132, 2000.
(3) G. R. Johnstone et al. Phytopathology (Abstr.) 74:795(A43), 1984.
(4) T. Tamada et al. Ann. Phytopathol. Soc. Jpn. 35:282, 1969.

[SbDV is transmitted by an aphid (_Acyrthosiphon (_Aulacorthum_) solani_ (some isolates also by _Acyrthosiphon pisum_) in a persistent manner. Both aphid species are present throughout the USA and also worldwide. Common names of _Acyrthosiphon (_Aulacorthum_) solani_ are pea aphid and green pea louse. For _Aulacorthum solani_, the common name is the foxglove aphid.

SbDV has been reported from Australia, Japan, New Zealand, and the USA (California). The 1st natural appearance of SbDV was in Blacksburg, Virginia in 1999. SbDV is serologically related to beet western yellows, barley yellow dwarf (strains RPV and MAV), bean leaf roll, potato leaf roll, and tobacco necrotic dwarf viruses. A 50 percent incidence of field infection may result in as much as 40 percent reduction in crop yield. Subterranean clover red leaf virus is so closely related that it is often considered to be the same species.

Regarding the reproductive (R) stages of soybean, there are 6 stages: R1, beginning bloom; R2, full bloom; R3, beginning pod; R4, full pod; R5, beginning seed; and R6, full seed. Link:<http://image.fs.uidaho.edu/vide/descr740.htm> - Mod.DH]