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  • Author or Editor: Noga Sikron x
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Petunia vein clearing virus (PVCV), a possible member of the caulimovirus group, was detected in several cultivars of vegetatively propagated petunias (Petunia ×hybrida Hort. Volm.-Andr.) grown in commercial nurseries. Leaf dip preparations and ultrathin sections of leaf tissue were analyzed by transmission electron microscopy (TEM). Spherical virus particles, 45-50 nm in diameter, were observed in samples taken from symptomatic petunia plants. The virus was purified and a polyclonal antiserum was prepared. In immuno-specific electron microscopy (ISEM), the PVCV antiserum-treated samples reacted with a distinct decoration on the virus suspect particles. A polymerase chain reaction (PCR)-based assay was used to detect PVCV in total nucleic acid extracts derived from infected petunia plants. Two primer pairs were designed to flank a 736-base-pair sequence located in the RNA-dependent RNA polymerase gene of the PVCV genome. A DNA fragment of predicted size was visualized in agarose gels. The authenticity of the amplified DNA fragment was confirmed by restriction analysis and by hybridization with the virus-specific PVCV DNA probe. The virus could be detected efficiently in high dilutions of sap extracted from infected petunia plants.

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In this study, 18 Petunia ×hybrida Hort. Volm.-Andr. cultivars were mechanically inoculated with the tobamoviruses tobacco mosaic (TMV) or tomato mosaic virus (ToMV) (20 μg·L-1 in 0.05 m sodium phosphate buffer). One and 2 weeks post-inoculation (PI), inoculated and noninoculated upper leaves were harvested and assayed for TMV infection using enzyme-linked immunosorbent assay (ELISA). Local lesions developed on inoculated leaves of 16 cultivars 3-5 days PI. A total of 11 and 16 of the cultivars developed systemic symptoms characteristic of tobamovirus infection 2 weeks after inoculation with TMV and ToMV, respectively. All cultivars were positive in ELISA tests. Large amounts of virus were recovered from the upper, noninoculated leaves of all cultivars, including symptomless plants. Up to 95% infection by TMV occurred when a sterilized knife was passed through an infected shoot of petunia prior to its being used to remove cuttings from healthy petunia plants. Heat sterilization of knives and/or treatment with 2.8 g·L-1 sodium troclosene was very effective in controlling TMV transmission.

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