Location: Plant Genetic Resources ResearchTitle: EST contig-based SSR linkage maps for Malus × domestica cv ‘Royal Gala’ and an apple scab resistant accession of M. sieversii, the progenitor species of domesticated apple) Author
Submitted to: Molecular Breeding
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/29/2011
Publication Date: 2/19/2011
Citation: Wang, A., Aldwinckle, H., Forsline, P., Main, D., Fazio, G., Brown, S., Xu, K. 2011. EST contig-based SSR linkage maps for Malus × domestica cv ‘Royal Gala’ and an apple scab resistant accession of M. sieversii, the progenitor species of domesticated apple. Molecular Breeding. DOI: 10.1007/s11032-011-9554-1. Interpretive Summary: Malus sieversii has been recognized widely as a major progenitor species for domesticated apple M. × domestica Borkh. Genetic maps are the key to unraveling and utilizing important traits for breeding and development of improved, diseases resistant apple cultivars. A new genetic map based on functional gene sequences was constructed. The map was utilized to identify the location of a novel gene for resistance to a devastating apple disease (apple scab) and to ascertain the location of other genes in the apple genome.
Technical Abstract: Malus sieversii has been recognized widely as a major progenitor species for domesticated apple M. × domestica Borkh. Several groups have been constructing genetic linkage maps for this important Malus species. Using an interspecific F1 population ‘4595’ of 188 individuals derived from a cross of ‘Royal Gala’ (M. × domestica) × PI 613988 (plant introduction number 613988, an apple scab resistant accession of M. sieversii), 280 SSR (simple sequence repeats) loci were mapped. Of these SSRs, 74 are published anchors (by 73 primer pairs) and 206 are newly developed EST (expressed sequence tag) contig-based SSRs (by 202 primer pairs), representing 1,621 Malus EST accessions in GenBank. Putative gene functions of these EST contigs are diverse, including regulating plant growth, development and response to environmental stresses. Among the 74 published SSR anchors, 16 are PI 613988 specific, 37 are common and 21 are ‘Royal Gala’ specific. Out of the 206 newly developed EST contig-based SSRs, 78 are PI 613988 specific, 44 are common and 84 are ‘Royal Gala’ specific. These results led to construction of an M. sieversii map of 175 SSR markers and a ‘Royal Gala’ map of 186 SSR markers. The M. sieversii map and the ‘Royal Gala’ map, both of which cover 17 linkage groups, have a total genetic distance of 1483.0 cM and 1327.5 cM, respectively. A putatively new apple scab resistance gene, designated Rvi18(t) tentatively, was mapped to linkage group 2 in M. sieversii. The utility of the two linkage maps and the new EST contig-based markers were discussed.