Studies on development of techniques for isolating virus resistance genes in tomato

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1.DNA markers nearest the Tm-1 and Tm-2 lociThe linear order of the known six DNA markers (SCAR markers) linked to the Tm-1 locus was not able to be determined, since they did not segregate m . progeny of a hybrid between near-isogenic tomato lines, GCR26 (+/+) and GC R237 ( Tm-2/Tm-2) . In another approach, we checked four Lycopersicon hirsutum lines. As a result, I101100 was estimated to be the nearest marker of the Tm-1 locus.Similarly, we attempted to determine the linear order of the known nine DNA markers (RAPD or SCAR markers) by comparing four tomato lines which have Tm-2 or one of the alleles of Tm-2. As a result, Nl3_<1000>, I13_<1300>, E16900 and, G09700 was estimated to be nearest the Tm-2 locus.2. Search for disease resistance gene-like sequences in near-isogenic tomato linesComparing patterns of PCR products and Southern hybridizatin patterns betwee the near-isogenic lines, we examined whether there are sequences different between near-isogenic lines, but failed to find any difference betweenthem.On the other hand, we found that there are a great number of resistance gene-like sequences, and was able to estimate a differentiation process of one sequence to .two differnt sequences.3. Detection of cDNA sequences specific to a ToMV resistant lineWe isolated cDNA fragments differentially displayed between GCR26 (+/+) and GCR236 (Tm-2/Tm-2) and determined their sequences. As a result, we found two fragments specific to GCR236, one of which has a sequence similar to apart of a gene encoding xyloglucan endo-transglycolase of tomato, and the other to a part of a gene encoding a protein kinase.