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

Abstract

This study aims to: (i) identify the Rosa S-locus controlling self-incompatibility (SI); (ii) test the genetic linkage of the S-locus with other loci controlling important ornamental traits, such as the continuous-flowering (CF) characteristic; (iii) identify the S-alleles (SC) of old Chinese CF cultivars (e.g, Old Blush, Slater’s Crimson China) and examine the changes in the frequency of cultivars with Sc through the history of breeding; (iv) identify wild species carrying the Sc-alleles to infer wild origins of CF cultivars. We identified a new S-RNase (SC2) of Rosa chinensis in a contig from a genome database that has not been integrated into one of the seven chromosomes yet. Genetic mapping indicated that SC2 is allelic to the previously-identified S-RNase (SC1) 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 F1-population indicated genetic linkage between the S-locus and the floral repressor gene KSN. The non-functional allele ksn is responsible for the CF characteristic. A total of five S-alleles (SC1–5) were identified from old CF cultivars. The frequency of cultivars with SC dramatically increased after the introgression of ksn from Chinese to European cultivars and remains high (80%) in modern cultivars, suggesting that S-genotyping is helpful for effective breeding. Wild individuals carrying SC were found in Rosa multiflora (SC1), Rosa chinensis var. spontanea (SC3), and Rosa gigantea (SC2, SC4), supporting the hypothesis of hybrid origins of CF cultivars and providing a new evidence for the involvement of Rosa multiflora.

Dark side of the honeymoon: reconstructing the Asian x European rose breeding history through the lens of genomics

“…g . Hibrand-Saint Oyant et al ., 2018, Kawamura et al ., 2022), which could therefore suggests the presence of tradeoffs between some traits of interest. A more detailed genomic characterization of the genomic landscapes, including local linkage disequilibrium patterns, based on more modern varieties, isespecially needed on this chromosome.…”

“…1). Such a continuous selection has likely contributed to generate a marked footprint of selection in rose genomes, since the sharpest signature of the selective sweep is observed above one of the two breaking points of a previously characterized 5-Mb inversion of the RoKSN gene (chromosome 3, 28.8 - 33.1 Mb, Hibrand-Saint Oyant et al ., 2018; Kawamura et al ., 2022). Consistent signal was also observed at the second breaking point (Fig.…”

“…Remarkably, the chromosome 3 has been associated to many traits in roses (resistance to black spot, but also number of petals, fragrance, prickles, recurrent blooming, self-incompatibility; e.g. Hibrand-Saint Oyant et al, 2018, Kawamura et al, 2022, which could therefore suggest the presence of tradeoffs between some traits of interests. A more detailed genomic characterization of the genomic landscapes, including local linkage disequilibrium patterns, based on more modern varieties, are especially needed on this chromosome.…”

“…3), including 15 on a 4-Mb region of the chromosome 3 (from 24.1 and 28.2 Mb, see Table S4). This region is in the immediate vicinity of a previously characterized 5Mb-inversion containing the RoKSN gene (28.8 -33.1 Mb, Kawamura et al 2022), a presumably main target breeding to obtain recurrent-blooming roses with an extended period of blooming. In addition, to these 18 windows, we detected 81 additional windows (last five centiles of the three metrics, pink lines in Fig.…”

RcSPL1–RcTAF15b regulates the flowering time of rose (Rosa chinensis)

“…According to their flowering habits, rose plants have been classified into the following three types: recurrent or continuous flowering (CF) (flowers bloom continuously under appropriate conditions); occasional re-blooming (OR) genotype (flowers bloom in spring and occasionally in autumn); and once-flowering (OF) (flowers bloom only in spring) [ 2 ]. Previous studies on the molecular basis of CF behavior mainly focused on the gibberellin (GA) pathway as well as on the floral repressor gene TERMINAL FLOWER 1 ( TFL1 ) [ 2 – 8 ]. However, CF seedlings have a short juvenile phase (4–5 weeks) with a determinate growth pattern, whereas OF seedlings have a long juvenile phase (1–3 years) with an indeterminate growth pattern [ 9 , 10 ].…”