Evidence for a third taxonomic subgroup of peanut stunt virus from China

On the basis of host reactions and serology, six Chinese peanut stunt virus (PSV) strains were found to be distinct from PSV-E and PSV-W, two type strains representing distinct serological subgroups. Chinese PSV strains were characterized by infecting Chenopodium amaranticolor and C. quinoa systemically. All Chinese strains were serologically closely related to each other, but distinct from PSV-E and more distant from PSV-W. Using two PSV-specific primers designed from conserved regions of the PSV RNA3 nucleotide sequence, cDNA transcribed from RNA3 of two Chinese PSV strains, Mi and S, was amplified by PCR and cloned. The sequenced cDNA of the two PSV strains included 654 nt of the coat protein (CP) gene. The identity of the CP gene nucleotide sequence between PSV-Mi and PSV-S was 99.0%, with 99.5% amino acid identity. Identity of the CP gene nucleotide sequence was 75.6 to 77.8% between PSV-Mi and -S (the two Chinese strains) and PSV-ER and -J in PSV subgroup I; and 74.1 to 74.4% between PSV-Mi and -S, and PSV-W in subgroup II. Based on these results, we propose placing PSV Chinese strains into a new PSV subgroup III.