First Report of a Mexican Isolate of Papaya mosaic virus in Papaya (Carica papaya) and Pumpkin (Cucurbita pepo).

Papaya mosaic virus (PMV) is a member of the Potexvirus group and has filamentous particles of 530 nm with a positive sense single-stranded RNA of 6.6Kb. PMV was detected in Mexico in diseased papaya plants growing alone and in mixed plantations with pumpkin. Reverse transcription polymerase chain reactions (RT-PCR) and standard double-antibody sandwich enzyme linked immunosorbent assay (DAS-ELISA) procedures were used on 45 leaf samples from single plants in seven locations in southeast Mexico (States of Yucatan, Campeche, and Quintana Roo). PCR primer design was based on a GenBank sequence with accession number D13957 (1). Amplified PCR products were cloned using a TOPO TA Cloning Kit and sequenced by the dideoxy chain termination method. Twenty-six samples tested positive for PMV using one or both detection techniques: 23 of 41 from papaya and three of four from pumpkin. The two sequences reported here, YY-15 and YY-22 (from papaya and pumpkin respectively, with accession numbers AYO17186 and AYO17187), were 1180 nucleotides long and contained a fragment of ORF3, the complete ORF4 and the putative CP gene, including the 3' end untranslatable region. Within the CP gene sequence, the amino acid sequence derived had a similarity of 88% with that of D13957 from the GenBank. The similarity of the CP between the two Mexican isolates (from papaya and pumpkin) was 94% and would therefore represent two variants of PMV. A healthy papaya plant in the greenhouse, inoculated with tissue from an infected papaya plant from the field, tested positive for PMV in DAS-ELISA. (PVX was used as a negative control). These results confirmed the identity of the isolate as PMV. Reference: (1) T. L. Sit, M. G. AbouHaidar, and S. Holi. J. Gen. Virol. 70:2335-2331, 1989.