On the origin of the sweet-smelling Parma violet cultivars (Violaceae): wide intraspecific hybridization, sterility, and sexual reproduction

摘要

Parma violets are reputed for their double, fragrant flowers and have been cultivated for centuries in Europe. However, due to anrather atypical morphology their taxonomic affinity has not been clarified. Authors have proposed an origin from three possiblenspecies, Viola alba, V. odorata, or V. suavis, or a hybrid origin. Using both ITS sequence variation and allozyme variation in 14nputative loci, we showed that the Parma violet cultivars have their origin within Viola alba and that they are best included in thenMediterranean subsp. dehnhardtii. There is no trace of interspecific hybridization. However, the cultivars appear to have a singlenorigin in a wide hybrid within V. alba, involving parental plants from the eastern and western Mediterranean region; historicalnliterature sources seem to indicate Turkey and Italy, respectively. The Parma violet cultivars possess high levels of allozymenheterozygosity and to some extent also within-individual ITS sequence variation. Losses of heterozygosity and within-individualnITS sequence variation in some of the cultivars indicate subsequent rare events of sexual reproduction, presumably throughncleistogamous seed set. We unambiguously identify the closest wild relative of this group of cultivars, allowing growers tondevelop new selection procedures, and show a peculiar molecular process associated with human selection.