Plant & Animal Genomes XI Conference Plant & Animal Genomes XI ConferenceJanuary 11-15, 2003
Town & Country Convention Center
San Diego, CA
Poster: Gene Isolation
The soil-borne fungus Fusarium oxysporum f.sp. melonis causes significant losses in melon production worldwide. The only economically feasible control measure available is the use of resistant cultivars. In melon, resistance to F. oxysporum races 0 and 1 is conferred by a single dominant gene; Fom-2 . Two codominant PCR based markers FM and SSR138 were found to flank Fom-2 at 0.7 and 0.4 cM, respectively. Using a chromosome walking approach, a single contig of BAC clones covering the genetic interval encompassing Fom-2 was constructed. Two BAC clones, found to span the Fom-2 physical interval were subjected to shotgun sequencing. In order to narrow down the interval containing Fom-2, markers were developed from putative SSR sequences distributed on the two BAC clones. Fom-2 was found in a 70-kilobase interval delimited by SSR244 and SSR278 markers. BLASTX search of this sequence against protein databases revealed the presence of 6 distinct sequences with similarity to polyproteins; 2 sequences with similarity to putative cleavage and polyadenylation specificity factors; and 1 sequence with similarity to an unknown gene. None of these genes have been previously characterized as conferring pathogen resistance in plants. To further narrow the Fom-2 physical interval, additional plant material segregating for Fom-2, SSR278 and SSR244 were screened with the SSR markers. A total of 6 plants presenting recombination between SSR278 and SSR244 were identified and their phenotype for resistance to F. oxysporum f.sp. melonis race 1 is being determined.