Truncated Rep gene originated from Tomato yellow leaf curl virus-Israel [Mild] confers strain-specific resistance in transgenic tomato

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 domain's 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.