Abstract
Old Chinese garden roses are the foundation of the modern rose, which is one of the best-selling ornamental plants. However, the horticultural grouping and evolution of old Chinese garden roses are unclear. Simple sequence repeat (SSR) markers were employed to survey genetic diversity in old Chinese garden roses and genetic differentiation was estimated among different rose groups. Fluorescence in situ hybridization was used to study the physical localization of 5 S rDNA genes and a karyotype analysis was performed. The SSR data suggest that old Chinese garden roses could be divided into Old Blush group, Odorata group and Ancient hybrid China group. The Old Blush group had the most primitive karyotype. The Ancient hybrid China group and modern rose had the most evolved karyotypes and the highest genetic diversity. During the evolution of rose cultivars, 5 S rDNA increased in number, partially weakened in signal intensity and exhibited variation in distance from the centromere. In conclusion, rose cultivars evolved from the Old Blush Group to the Odorata group, the Ancient Hybrid China group and the modern rose. This work provides a basis for the collection, identification, conservation and innovation of rose germplasm resources.
Highlights
Plant breeding aims to combine traits of interest with existing traits
Both China roses and Tea roses are everblooming erect shrubs belonging to old Chinese garden roses, but they do not represent all of the old Chinese garden rose germplasm
The first goal of this study was to determine whether the Old Blush group is genetically distinct from other ever-blooming China roses
Summary
Plant breeding aims to combine traits of interest with existing traits. The conservation and innovation of germplasm resources are the foundation of breeding programs. Cultivated roses are mostly horticulturally classified into three groups based on phenotypic characters: (i) wild species or botanical roses, (ii) old garden roses that existed prior to 1867 and (iii) modern roses[8]. As a subdivision of old garden roses, refer to the group that includes Rosa chinensis in sect. Tea roses (i.e. Tea-scented China roses) are continuous-flowering roses, named for their scent, which resembles that of Chinese black tea; they have individual flowers with petals that tend to roll back at the edge[8]. It is crucial to clarify the grouping, genetic relationships, and early breeding process of old Chinese garden roses. Few studies have combined cytogenetic techniques and molecular biology techniques to analyse the genetic relationships and evolution of old Chinese garden roses
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