Marker-Locus-Trait Associations
A marker-locus-trait (M-L-T) association is a predictive genetic marker developed for specific locus that contribute to genetic variation for [read more...]
a specific trait (Bliss 2010). We typically know these as simply “markers”, or “marker-trait associations”, or in some cases, “gene-trait associations”. The three-level concept takes into account the hierarchical nature of these predictive genetic tools.
A given trait may be under the genetic control of a single genetically variable locus (i.e., major trait loci, also known as Mendelian trait loci or simply inherited traits), but are often influenced by several genetically variable loci (i.e. quantitative trait loci). An M-L-T association defines which locus is under consideration. Then for any given locus there can be many specific markers developed. For example, one marker for a locus could be a RAPD assay fragment that is 10 cM from the locus but can still be a predictive marker for that locus. Another marker might be an SSR, based on primers developed for a microsatellite 240 bp upstream from the start codon of the gene itself. A different set of primers developed for the same microsatellite would be a different marker. Yet another marker may be a simple PCR marker developed for a 10 bp indel in the second intron of the gene. Another could be a SNP somewhere in the coding sequence. HIghly heritable morphological characters can also be useful markers, such as “red leaf color”.
Bliss F.A. 2009. Marker-assisted breeding in horticultural crops. Acta Horticulturae (in press) (Proceedings of the ISHS Symposium on Molecular Markers in Horticulture, Corvallis, Oregon, USA, 29 Jul – Aug 1 2009)
• Download the detailed list of Marker-Locus-Trait Associations in Rosaceae
• Summary of Marker-Locus-Trait Associations in Rosaceae
| Crop | Number of | Number used in | ||||||
| Traits | QTLsa | Majorb | Genesc | MAPSd | MASSe | |||
| Apple | 55 | 180 | 36 | 5 | 3 | 1 | ||
| Pear | 5 | 7 | 3 | 1 | 0 | 0 | ||
| Peach | 21 | 36 | 4 | 2 | 1 | 0 | ||
| Almond | 10 | 8 | 4 | 1 | 1 | 0 | ||
| Cherry (sweet) | 3 | 2 | 0 | 1 | 2 | 0 | ||
| Cherry (tart) | 3 | 14 | 0 | 1 | 1 | 0 | ||
| Strawberry | 11 | 31 | 2 | 0 | 0 | 2 | ||
| Raspberry | 0 | 0 | 0 | 0 | 0 | 0 | ||
| Blackberry | 0 | 0 | 0 | 0 | 0 | 0 | ||
| Rose | 11 | 41 | 9 | 0 | 0 | 0 | ||
aQTLS = quantitative trait loci with linked markers
bMajor = major trait loci with linked markers
cGenes = known genes (i.e., with known DNA sequence) controlling a trait
dMAPS = marker-assisted parent selection
eMASS = marker-assisted seedling selection