Natural Occurrence of Groundnut ringspot virus on Soybean in South Africa.

Abstract

Mechanically transmissible viruses were isolated from two soybean (Glycine max Merr.) plants from Rustenburg, Northwest Province and Greytown, KwaZulu-Natal, South Africa, respectively (2). Viruses were isolated by two serial local-lesion transmissions on Chenopodium quinoa. Ringspot symptoms on Nicotiana benthamiana suggested the presence of tospoviruses. This was supported by the detection of typical tospoviruslike particles in ultrathin sections of infected plants. Serological analysis of samples using various tospovirus antisera in a number of enzymelinked immunosorbent assay formats suggested the two isolates had epitopes in common with Tomato spotted wilt virus (TSWV), Groundnut ringspot virus (GRSV), and Tomato chlorotic spot virus (TCSV). Nucleotide sequences were determined using reverse transcriptionpolymerase chain reaction (RT-PCR) for 857 bp of the nucleoprotein gene of the two isolates (GenBank Accession Nos. AF487516 and AF 487517). These revealed a 99% nucleotide identity with each other. Sequence comparison with cognate regions of TSWV (GenBank Accession No. D00645), GRSV-SA-05 (GenBank Accession No. S54327), and TCSV (GenBank Accession No. S54325) revealed that both isolates share 97% nucleotide sequence identity with GRSV (SA-05) from peanut also originally from South Africa (1). Both isolates are therefore considered GRSV. To our knowledge, this is the first report of the natural occurrence of GRSV on soybean worldwide.