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RAPD AND SCAR MARKERS LINKED TO THE LOCI OF TOMATO MOSAIC VIRUS RESISTANCE GENES Tm-1 AND Tm-2 IN TOMATO AND ITS WILD RELATIVES
RAPD AND SCAR MARKERS LINKED TO THE LOCI OF TOMATO MOSAIC VIRUS RESISTANCE GENES Tm-1 AND Tm-2 IN TOMATO AND ITS WILD RELATIVES F MOTOYOSHI, T OHMORI AND M. MURATA Research Institute for Bioresources, Okayama University, Kurashiki 710, Japan Background and objectives Tomato mosaic virus (TOMV) resistance genes Tm-1 and Tm-2 in tomato is derived from Lycopersicon hirsutum and L. peruvianum, respectively. Tm-1 is located near the RDNA on the distal region of the short arm of chromosome 2, while Tm-2 resides in the heterochromatic region near centromere of chromosome 9. Another TOMV resistance gene Tm-2a derived from L. peruvianum is allelic to Tm-2. Tm-1 is presumed to prevent replication of the genomic RNA of TOMV, and Tm-2 to prevent movement of virus from cell to cell. The function of Tm-2a may be similar to Tm-2, because they are allelic and the phenotypes resemble from each other. For further understanding on the functions of Tm-1 and Tm-2, cloning of the genes may be necessary. Positional cloning is an ordinary way to isolate a gene whose product is unknown. As the first step for cloning Tm-1 and Tm-2, DNA markers closely linked to them must be identified. Results and concludions Six random amplified polymorphic DNA (RAPD) markers linked to the Tm-1 locus were identified, and converted into sequence characterized amplified region(SCAR) markers. The linear order of these markers and the Tm-1 locus could not been determined, since they did not segregate in progeny of a hybrid between near-isogenic lines (NILS) of tomato, GCR26 and GCR237,whosegenotypesare+/+andTm-l/Tm-l, respectively[l,2]. ln another approach, we examined which markers are present in some other Tm-1 lines, and confirmed that they have all the six markers. We then checked four L. hirsutum lines, LA94, LA386, LA1 361 and LA2174. As a result, only LA2174 which has three SCAR markers, Bl01300, N201400 and 1101100, was found to be ToMV-resistanct. It remains, however, to be confirmed whether it is really Tm-l that confers the ToMV-resistance in LA2174. Ten RAPD markers were identified to be linked to Tm-2 within about 5 cM, and six of them did not segregate in progeny of a hybrid between NILS, GCR26 (+/+) and GCR236 (Tm-2/Tm-2) [3]. We examined which RAPD (or SCAR) markers are present in two other lines, GCR267 homozygous for Tm-2a and TMJ54-28 homozygous for a Tm-2-like gene alielictoTm-2, As a result, three RAPD (orSCAR) markers, N131000,E16900andGO9700, out of the six markers were found in GCR267 and TMJ54-28. In addition to these markers, two RAPD markers, 11 31300 and Ml 61250 were found in GCR236, GCR267 and TMJ54-28, but not in GCR26 (+/+). L. peruvianum P.l. 128650, from which Tm-2a had been introgressed into tomato, was comfirmed to have N131000, El 6900 and G09700. Through this study, we selected RAPD or SCAR markers possibly useful for cloning of the Tm-1andTm-2loci. lnadditiontothepotentialusefulnessformap-basedcloningofthe genes, we can make use of these markers in breeding, especially for replacing the wild species-derived regions surrounding these TOMV resistance gene loci by the homologous tomato regions, References 1. Ohmori T, Murata M, Motoyoshi F, 1995. The Japanese Journal of Genetics 70: 179-184 2. Ohmori T, Murata M, Motoyoshi F, 1996. Theoretical and Applied Genetics 92: 151-156 3. Ohmori T, Murata M, Motoyoshi F, 1995. Theoretical and Applied Genetics 90: 307-311