The identification of the Rosa S -locus provides new insights into the breeding and wild origins of continuous-flowering roses.

This study aims to: (i) identify the -locus controlling self-incompatibility (SI); (ii) test the genetic linkage of the -locus with other loci controlling important ornamental traits, such as the continuous-flowering (CF) characteristic; (iii) identify the -alleles ( ) of old Chinese CF cultivars (e.g, Old Blush, Slater's Crimson China) and examine the changes in the frequency of cultivars with through the history of breeding; (iv) identify wild species carrying the -alleles to infer wild origins of CF cultivars. We identified a new - ( ) of in a contig from a genome database that has not been integrated into one of the seven chromosomes yet. Genetic mapping indicated that is allelic to the previously-identified ( ) in chromosome 3. Pollination experiments with half-compatible pairs of roses confirmed that they are the pistil-determinant of SI. The segregation analysis of an -population indicated genetic linkage between the -locus and the floral repressor gene The non-functional allele is responsible for the CF characteristic. A total of five -alleles ( ) were identified from old CF cultivars. The frequency of cultivars with dramatically increased after the introgression of from Chinese to European cultivars and remains high (80%) in modern cultivars, suggesting that -genotyping is helpful for effective breeding. Wild individuals carrying were found in ( ), var ( ), and ( , ), supporting the hypothesis of hybrid origins of CF cultivars and providing a new evidence for the involvement of .