|Egel, D. S.|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2007
Publication Date: 8/1/2007
Citation: Egel, D., Adkins, S.T. 2007. Squash vein yellowing virus identified in watermelon in Indiana. Plant Disease. 91:1056. Interpretive Summary: This is the first report of Squash vein yellowing virus (SqVYV) outside of Florida. A description of the host, symptoms and diagnostic methods used to confirm the identity of SqVYV are presented. This report initiates a cooperative research effort between ARS and Purdue University, and provides a timely account of SqVYV infection of watermelon in Indiana to growers, Extension personnel and state and Federal regulatory and research scientists.
Technical Abstract: In September 2006, a commercial watermelon field in Sullivan County,Indiana was observed with moderate vine decline symptoms including vine collapse, wilt and root rot. No fruit symptoms were observed. Six plants displaying typical vine decline symptoms were collected and assayed for potyviruses in general, and Squash vein yellowing virus (SqVYV, a whitefly-transmitted member of the Potyviridae recently shown to cause a watermelon vine decline in Florida; 1,2) and Papaya ringspot virus type W (PRSV-W) in particular All samples harbored one or more potyviruses as determined with a commercially available enzyme linked immunosorbent assay (ELISA; Agdia, Elkhart, IN). Mechanical inoculation of squash and watermelon with sap from field samples resulted in mosaic symptoms typical of potyviruses, and vein yellowing in squash and plant death in watermelon typical of SqVYV (2). A coat protein gene fragment was amplified by reverse transcription-polymerase chain reaction (RT-PCR) with SqVYV primers (2) from total RNA of the symptomatic, inoculated plants. Nucleotide and deduced amino acid sequences of a 957 base pair region of the RT-PCR product were 100% identical to SqVYV (accession number DQ812125). PRSV-W also was identified in several Indiana samples by ELISA (Agdia) and by sequence analysis of a 3’ genome fragment amplified by RT-PCR with previously described degenerate potyvirus primers (3), similar to what has been observed with vine decline in Florida (2). Although these experiments confirmed the presence of SqVYV in Indiana in 2006, for the first time outside of Florida, it is unlikely that SqVYV will reach the severity in Indiana that it has in Florida. The whitefly (Bemisia tabaci, B strain) vector of SqVYV is relatively uncommon in Indiana and the cold winter temperatures make it unlikely that any SqVYV-infected watermelon vines or whiteflies will overseason, necessitating reintroductions of virus and vector each season. The occurrence of SqVYV in Indiana does not appear to be related to the sporadic occurrence of mature watermelon vine decline (MWVD) observed in Indiana since the 1980’s (4). Unlike the vine decline induced by SqVYV, fruit symptoms have never been observed with MWVD (2,4). Additionally, MWVD appears to be caused by a soil borne agent (4). The moderate and restricted occurrence of SqVYV in Indiana in September 2006 should pose little or no threat to commercial watermelon production in Indiana and should not cause growers to alter their growing practices.