Genetic dissection of adventitious shoot regeneration in roses by employing genome-wide association studies.

We analysed the capacity to regenerate adventitious shoots in 96 rose genotypes and found 88 SNP markers associated with QTLs, some of which are derived from candidate genes for shoot regeneration. In an association panel of 96 rose genotypes previously analysed for petal colour, we conducted a genome-wide association study on the capacity of leaf petioles for direct shoot regeneration. Shoot regeneration rate and shoot ratio (number of shoots/total number of explants) were used as phenotypic descriptors for regeneration capacity. Two independent experiments were carried out with six replicates of ten explants each. We found significant variation between the genotypes ranging from 0.88 to 88.33% for the regeneration rate and from 0.008 to 1.2 for the shoot ratio, which exceeded the rates reported so far. Furthermore, we found 88 SNP markers associated with either the shoot regeneration rate or the shoot ratio. In this association analysis, we found 12 SNP markers from ESTs (expressed sequence tags) matching known candidate genes that are involved in shoot morphogenesis. The best markers explained more than 51% of the variance in the shoot regeneration rate and more than 0.65 of the variance in the shoot regeneration ratio between the homozygote marker classes. The genes underlying some of the best markers such as a GT-transcription factor or an LRR receptor-like protein kinase are novel candidate genes putatively involved in the observed phenotypic differences. The associated markers were mapped to the closely related genome of Fragaria vesca and revealed many distinct clusters, which also comprised the known candidate genes that functioned in the organogenesis of plant shoots. However, the validation of candidate genes and their functional relationship to shoot regeneration require further analysis in independent rose populations and functional analyses.