Trichosanthes cucumerina L., known as snake gourd, is a cucurbitaceous plant that is probably native to and originally domesticated in India. It is cultivated in humid subtropical and tropical countries of Australia, Latin America, and Africa (2). Plants of this species exhibiting symptoms of mosaic and leaf malformation were found during November 2008 near an experimental field of the Departamento de Fitopatologia e Nematologia, Universidade de São Paulo, Piracicaba, State of São Paulo, Brazil. Electron microscopy examination of negatively stained extract of infected tissue showed the presence of filamentous potyvirus-like particles. Sap from these infected plants reacted in plate-trapped antigen (PTA)-ELISA with the antiserum against Papaya ringspot virus--type W (PRSV-W) or Zucchini yellow mosaic virus (ZYMV), but not with the antiserum against Cucumber mosaic virus (CMV) or Zucchini lethal chlorosis virus (ZLCV). PRSV-W and ZYMV were simultaneously transmitted by mechanical inoculation to four plants of Cucurbita pepo cv. Caserta and one plant of T. cucumerina, causing mosaic. In addition, PRSV-W and ZYMV isolates from our virus collection separately infected one plant of T. cucumerina after mechanical inoculation. Infections were confirmed by PTA-ELISA. Total RNA extracted from infected and healthy T. cucumerina was analyzed by reverse transcription (RT)-PCR using a primer pair specific to the coat protein (CP) gene of PRSV-W (4) or ZYMV (3). Fragments of 864 bp and 1,045 bp were amplified with each pair of primers, respectively. Nucleotide sequences directly obtained from purified PCR products were used for further identification of these potyviruses. The nucleotide and deduced amino acid sequences of part of the CP gene (792 nt) of PRSV-W (GenBank Accession No. GU586789) shared 99 and 98% identity, respectively, with that of the Brazilian isolate PRSV-W-C (GenBank Accession No. 4152). The nucleotide and deduced amino acid sequences of the entire CP gene (837 nt) of ZYMV (GenBank Accession No. 6790) shared 91 to 98% and 94 to 100% identity, respectively, with innumerous isolates of ZYMV deposited in the GenBank (e.g., Accession Nos. AB004640, D13914, AB004641, and AJ420019). Natural infection of T. cucumerina by PRSV-W was reported in Nepal (1). To our knowledge, this is the first report of T. cucumerina infected by PRSV-W and ZYMV in Brazil.
References: (1) G. Dahal et al. Ann. Appl. Biol. 130:491, 1997. (2) R. W. Robinson and D. S. Decker-Walters. Cucurbits. CAB International, Wallingford, UK. 1997. (3) K. G. Thomson et al. J. Virol. Methods 55:83, 1995. (4) M. G. S. D. Vechia. Fitopatol. Bras. 28:678, 2003.
