The 2012 ASHS Annual Conference

The first genetic map of American cranberry (Vaccinium macrocarpon Ait.) has been constructed, comprising 14 linkage groups totaling 879.9 cM with an estimated genome coverage of 82.2%. This map, based on four mapping populations segregating for field fruit rot resistance, contains 136 distinct loci, and provides the first foray in the identification of regions associated with fruit rot resistance. Mapped markers include blueberry simple sequence repeat (SSR) and cranberry sequence-characterized amplified region (SCAR) markers previously used for fingerprinting cranberry cultivars. In addition, SSR markers were developed near cranberry sequences resembling genes involved in flavonoid biosynthesis or defense against necrotrophic pathogens, or conserved orthologous set (COS) sequences. The cranberry SSRs were developed from next-generation cranberry genomic sequence assemblies; thus, the positions of these SSRs on the genomic map provide information about the genomic location (but not the orientation) of the sequence scaffold from which they were derived. The use of SSR markers near functional sequences, in particular the COS-associated SSRs, plus 33 SSR markers from blueberry, enables comparisons of the cranberry map with other plant species’ maps. Regions of the cranberry map showing synteny with grape, and a more limited conservation with A. thaliana, were identified. The cranberry map utilized markers that are highly informative and readily transferrable to other crosses and closely-related species. Located on this map are quantitative trait loci (QTL) for field fruit rot resistance (FFRR, three loci), fruit weight (two loci), titratable acidity (one locus), and sound fruit yield (one locus). The sound fruit yield QTL was located near one of the fruit weight QTL, but might be pleiotropic. Two of the FFRR QTL are in regions of conserved synteny with grape and span defense gene markers, and the third FFRR QTL spans a flavonoid biosynthetic gene, however, functional attribution at this point is premature. Ultimately, a more densely populated map will be required, resulting in the 12 linkage groups which comprise the cranberry karyotype. This map will be used to facilitate future cranberry breeding efforts, particularly for improving fruit rot resistance.