A New Potyvirus found in Passiflora incence in Florida

During March of 2004 (Alachua County) and again during February of 2006 (Highlands County), specimens of the plant Passiflora incence (passionfruit) with chlorotic symptoms were submitted to the Division of Plant Industry, Gainesville, FL for diagnosis. Cytoplasmic cylindrical inclusions seen in epidermal strips of plant leaves stained in Luxol brilliant green and calcomine orange but not seen in those stained in Azure A indicated the presence of a potyvirus infection. Leaf dips made for electron microscopy also showed virus particles consistent with a potyvirus infection. Reverse-transcription (RT)-PCR using degenerate potyvirus primers (4) produced a target ≈1.7-kb potyvirus band. Approximately 1.4 kb of the PCR fragments from both specimens was sequenced and was 100% identical. The 1.4-kb fragment contained the 3' end of the NIb region, the coat protein, and the beginning of the 3'UTR. A GenBank BLAST search found that the two most similar potyviruses were Bean common mosaic necrosis virus (BCMNV), also known as serotype A of Bean common mosaic virus (BCMV), and Soybean mosaic virus (SMV). Molecular analysis of the 1.4-kb sequence using MegAlign (DNASTAR, Madison, WI) indicated a 73% identity with BCMNV and 68.8% with SMV. Analysis of the coat protein showed the highest identity (87%) with BCMNV, and for the NIb region, the highest identity occurred with SMV at 78%. In double-antibody sandwich (DAS)-ELISA, the virus did not react with antisera to either BCMV or BCMNV (BioReba). In sodium dodecyl sulfate (SDS)-immunodiffusion tests, however, the virus reacted heterologously with antiserum to Peanut stripe virus, now considered a member of the serotype B group of BCMV (1). In host range studies, this virus induced systemic chlorosis in Chenopodium quinoa but did not cause symptoms on any other host inoculated, including eight leguminous species and Nicotiana benthamiana. N. bethamiana is susceptible to BCMV and three other known Passiflora potyviruses, Passionfruit crinkle virus (PCV), Passionfruit woodiness virus (PWV), and Passionfruit mottle virus (PFMoV) (2,3). The cylindrical inclusions of this virus seen with the light microscope appeared as loosely aggregated medium length plate or needle-like structures as opposed to long, compact, bundle-shaped aggregates (PFMoV and PCV) or short plate-like structures (PWV) (2,3). The virus did not react with antisera (W. Zettler, University of Florida) to the three aforementioned passionfruit potyviruses in SDS-immunodiffusion tests. This virus, like PCV, PWV, and PFMoV, is related to the Bean common mosaic virus group. However, based on cylindrical inclusion morphology, host range, serology, and genetic sequencing, the virus appears to be a new potyvirus infecting Passiflora and is tentatively named Passiflora chlorosis virus. The sequence was deposited in GenBank as Accession No. DQ860147. References: (1) A. A Brunt et al. Plant Viruses Online: Descriptions and Lists from the VIDE Database. Version 20, August 1996. (2) C. A. Chang. Phytopathology. 82:1358, 1992 (3) C. A. Chang et al. Plant Prot. Bull. 38:339, 1996. (4) A. Gibbs and A. Mackenzie. J. Virol. Methods 63:9, 1997.