Molecular typing and history of the provins roses horticultural group

Summary A molecular typing analysis by random amplified polymorphic DNA (RAPD) was performed on a 281 cultivar collection of Gallica roses from the conservatory of the Roseraie de la Cour de Commer in France. A principal component analysis of the PCR data produced a map of distances among cultivars. The identification of cultivars by date of creation and breeder reveals the occurrence of 2 allele flows in opposite directions during the domestication history (nineteenth and twentieth centuries) of this horticultural group. The first flow corresponds to an increased molecular polymorphism of PCR fragments resulting from a higher heterozygosity. This increased polymorphism is due to extensive crosses between Gallica cultivars and selection of cultivars with original morphologies and heterosis. The second flow corresponds to the achievement of interspecific crosses of Gallica (4n) cultivars by Rosa chinensis (2n) and parent cultivars. These crosses resulted in the introgression of chinenses characters (red colouration of young follicles and recurrence) together with a decrease of the molecular polymorphism probably due to some reduction of polyploidy and/or heterozygosity. Descriptions in the horticultural literature of the pollination practices suggests that the many Gallica cultivars corresponding to the first allele flow were created by productive breeders using simple cross intraspecific pollinations between Gallica cultivars. The few cultivars corresponding to the second flow were created by careful breeders who practised strict interspecific pollinations between Gallicas and Chinenses roses.