Members of the genus Sorbus are the only endemic tree species that occur in Czechia. They are important components of endangered plant communities. Their natural regeneration is usually problematic because of their mode of reproduction and because they can survive in rare populations with small numbers of individuals. The aim of this study was to develop a successful micropropagation protocol for selected Sorbus species, of which two are endemic (S. gemella and S. omissa) and two are hybrid (S. × abscondita and S. × kitaibeliana). We found significant differences in shoot induction and rooting ability between the Sorbus species under study. With the exception of S. × abscondita, N6-benzyladenine had a significantly greater effect on shoot regeneration, both in terms of shoot number and total shoot length, than meta-topolin. Root induction was key to the successful micropropagation of the Sorbus species studied. Our results show that four Sorbus species can be successfully rooted under ex vitro conditions, without a rooting powder treatment in a steamed peat-perlite substrate. Auxin-untreated microcuttings of S. gemella, S. × kitaibeliana and S. omissa, but not S. × abscondita, rooted better than ones treated with indole-3-butyric acid. This is the first time a micropropagation protocol for S. omissa, S. × abscondita and S. × kitaibeliana has been published.
This paper presents the results of extensive field research on the occurrence of Rubus L. species in the Czech Republic, especially in the frontier areas near the German border. In this area, Rubus adornatus, R. fasciculatiformis and R. perlongus were newly discovered. The other species, R. ambulans and R. stohrii, were discovered in the eastern and northern parts of Bohemia. A description, an illustration, photos and a list of localities are provided for each species. Taxonomy and nomenclature, ecology, distribution and etymology are discussed. The ploidy level of the mentioned species is presented here for the first time. All of these species are new for the flora of the Czech Republic.
A complicated assemblage of names for taxa of hybrid origin between the Sorbus aria agg. and S. aucuparia (S. subg. Soraria) was analysed with the aim of separating the names of diploid hybrids from those of polyploid apomictic species and evaluating them nomenclaturally. Several names were found to be invalid, illegitimate, acceptable only for cultivated clones (cultivars), or representing indefinite taxa. Only one legitimate name was found to be available as the correct name of the diploid hybrid S. aria s.str. × Sorbus aucuparia, i.e., S. ×thuringiaca, with a newly designated lectotype.
Rubus violaceifrons, a new species from central and north-eastern Bohemia (Czech Republic) is described and illustrated, and its distribution is characterized in detail. We classify it as a member of the series Pallidi of the subgenus Rubus, section Rubus and subsection Hiemales, although its weak specimens partly resemble R. guentheri from ser. Glandulosi. Like all species of R. ser. Pallidi studied so far, R. violaceifrons is tetraploid, as determined using flow cytometry. A detailed morphological comparison of the new bramble species with similar taxa is presented. A determination key including all taxa of the R. ser. Pallidi occurring in the Czech Republic is provided.
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