Mosaic Disease of Calla Lily Caused by a New Potyvirus in Taiwan

Abstract

In 1998, a new mosaic disease of calla lily (Zantedeschia spp.) was found in Taichung County, Taiwan. Primary symptoms were mosaic and green islands on leaves and discolored spots on flowers. Symptomatic plants were negative in double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) for Dasheen mosaic virus (DsMV) polyclonal antibody (Agdia Inc., Elkhart, IN), but were positive in indirect ELISA using an anti-potyvirus group monoclonal antibody. Extracts from these plants were infective by mechanical inoculation to seedlings of calla lily and Philodendron selloum, which expressed veinal chlorosis, mosaic, and green island symptoms. Transmission electron microscopic analysis indicated that the virus particles purified from inoculated P. selloum were 695 to 845 nm long. In addition, potyvirus-specific cytoplasmic inclusions were observed in epidermal cells of infected calla lily. The 3′-terminal region of the virus was amplified by reverse-transcription polymerase chain reaction from total RNA or viral RNA using a potyvirus-specific degenerate primer and an oligo(dT) primer. A 1.6-kb amplified fragment was cloned, and three independent clones were sequenced. The sequences included a portion of NIb gene, the coat protein (CP) gene, the 3′ untranslated region (3′UTR) and the poly(A) tail. This nucleotide sequence (GenBank Accession No. AF332872) was checked against the international sequence databases using the BLAST program (provided by National Center for Biotechnology Information online at www.ncbi.nlm.nih.gov/blast/ ). The highest identity of the CP amino acid sequences between this unknown virus and other potyviruses is 68%. Amino acid sequence homologies for the CPs between individual potyviruses are 38 to 71%, while those between strains of a potyvirus are more than 90% (1). Therefore, this Zantedeschia-infecting virus is a previously undescribed potyvirus and is herein designated as Zantedeschia mosaic virus (ZaMV). In further analyses, the amino acid sequence identities of the CP gene between ZaMV and 13 other aphid-transmitted potyviruses were 46 to 61% and 9 to 23% for the nucleotide sequence of the 3′UTR. ZaMV and DsMV showed 46% identity in the CP amino acid sequence and 12% identity in the 3′UTR nucleotide sequence, indicating that they are two distinct members of the genus Potyvirus. To our knowledge, this is the first report of natural infection of Zantedeschia spp. by ZaMV, a new potyvirus identified in Taiwan. Reference: (1) D. D. Shukla and C. W. Ward. Arch. Virol. 106:171, 1989.