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Transgenic tomato plants carrying a truncated replication associated protein (T-Rep) gene of the mild strain of Tomato yellow leaf curl virus-Israel (TYLCV-Is [Mild]) were prepared. The transgene encoding the first 129 amino acids of Rep conferred resistance only against the virus strain from which it was derived, while these plants were susceptible to the severe strain of TYLCV-Is. This strain-specific effect may be the result of high sequence divergence within the N-terminal domains of the Rep genes of the two virus isolates which share a mere 78% sequence identity at the nucleotide level and 77% at the amino acid level. Although the transgenic tomato plants were totally resistant to whitefly inoculation with the mild strain of TYLCV-Is, agroinoculation with the same virus strain resulted in variable resistance responses in the tested plants: while 21% of plants were totally immune to the virus, 33% were susceptible and 46% expressed a wide range of intermediate resistance characteristics. The applicability of TYLCV-Is derived resistance in tomato is discussed. [ABSTRACT FROM AUTHOR]

Summary. A virus was isolated from Verbena plants that bore virus-like symptoms. The virus, for which the name Verbena latent virus (VeLV) is proposed, was consistently isolated from these plants, both with and without disease symptoms. Electron microscopy studies of ultrathin sections of infected Verbena tissues revealed the presence of elongated flexuous virus particles, ca. 650 nm in length. Its experimental host range was limited to Verbena spp. and Nicotiana clevelandii. No inclusion bodies or specific cytopathological effects, were observed. Electrophoresis of dissociated purified virus preparation in sodium dodecyl sulfate-polyacrylamide gel revealed a major protein component with a molecular mass of 38.9 kDa. Polyclonal antibodies which could specifically bind to virus particles were produced. A portion of the viral RNA was cloned and sequenced; it comprised 2503 nucleotides and contained part of three open reading frames (ORFs) which from the 5′ to the 3′-ends, potentially encode for 489 amino acids (ORF1), a 25.8-kDa protein (ORF2) and a 12-kDa protein (ORF3). Comparison of the predicted amino acid sequence with those of other plant viruses revealed 40–60% identity with several carlaviruses. In the light of particle morphology, absence of specific cytopathological effects in ultrathin sections, and genomic and serological properties, it is suggested that this virus belongs to the genus Carlavirus. [ABSTRACT FROM AUTHOR]