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Article|01 Oct 2022|OPEN
The identification of the Rosa S-locus provides new insights into the breeding and wild origins of continuous-flowering roses
Koji Kawamura1 , , Yoshihiro Ueda2,3 , Shogo Matsumoto4 , Takanori Horibe4,5 , Shungo Otagaki4 , Li Wang6 , Guoliang Wang7,8 and Laurence Hibrand-Saint Oyant9 , Fabrice Foucher9 , Marcus Linde10 , Thomas Debener,10
1Department of Environmental Engineering, Osaka Institute of Technology, Japan
2Gifu International Academy of Horticulture, Japan
3Gifu World Rose Garden, Japan
4Graduate School of Bioagricultural Sciences, Nagoya University, Japan
5College of Bioscience and Biotechnology, Chubu University, Japan
6College of Life Sciences, Sichuan University, China
7Jiangsu Provincial Department of Agriculture and Rural Affairs, China
8Agricultural University of Nanjing, China.
9Univ Angers, INRAE, Institut Agro, IRHS, SFR QUASAV, F-49000 Angers, France
10Leibniz Universität, Hannover, Germany
*Corresponding author. E-mail: koji.kawamura@oit.ac.jp

Horticulture Research 9,
Article number: uhac155 (2022)
doi: https://doi.org/10.1093/hr/uhac155
Views: 226

Received: 28 Feb 2022
Accepted: 03 Jul 2022
Published online: 01 Oct 2022

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 (SC2SC4), supporting the hypothesis of hybrid origins of CF cultivars and providing a new evidence for the involvement of Rosa multiflora.