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

Koji Kawamura; Yoshihiro Ueda; Shogo Matsumoto; Takanori Horibe; Shungo Otagaki; Li Wang; Guoliang Wang; Laurence Hibrand-Saint Oyant; Fabrice Foucher; Marcus Linde; Thomas Debener

doi:10.1093/hr/uhac155

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

Hortic Res. 2022 Feb 28:9:uhac155. doi: 10.1093/hr/uhac155. eCollection 2022.

Authors

Koji Kawamura¹, Yoshihiro Ueda^{2

3}, Shogo Matsumoto⁴, Takanori Horibe^{4

5}, Shungo Otagaki⁴, Li Wang⁶, Guoliang Wang^{7

8}, Laurence Hibrand-Saint Oyant⁹, Fabrice Foucher⁹, Marcus Linde¹⁰, Thomas Debener¹⁰

Affiliations

¹ Department of Environmental Engineering, Osaka Institute of Technology, Japan.
² Gifu International Academy of Horticulture, Japan.
³ Gifu World Rose Garden, Japan.
⁴ Graduate School of Bioagricultural Sciences, Nagoya University, Japan.
⁵ College of Bioscience and Biotechnology, Chubu University, Japan.
⁶ College of Life Sciences, Sichuan University, China.
⁷ Jiangsu Provincial Department of Agriculture and Rural Affairs, China.
⁸ Agricultural University of Nanjing, China.
⁹ Univ Angers, INRAE, Institut Agro, IRHS, SFR QUASAV, F-49000 Angers, France.
¹⁰ Leibniz Universität, Hannover, Germany.

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 (S_C ) 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 (S_C2 ) 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 S_C2 is allelic to the previously-identified S-RNase (S_C1 ) 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 (S_C1-5 ) were identified from old CF cultivars. The frequency of cultivars with S_C 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 S_C were found in Rosa multiflora (S_C1 ), Rosa chinensis var. spontanea (S_C3 ), and Rosa gigantea (S_C2 , S_C4 ), supporting the hypothesis of hybrid origins of CF cultivars and providing a new evidence for the involvement of Rosa multiflora.