Constituents of sexual diploid St. John's wart plants (Hypericum erforatum L.) in comparison with the tetraploid facultatively apomictic cultivar 'Topaz'
St. John's wort (Hypericum perforatum L.) reproduces primarily by apomixis. However, breeders need sexual lines to combine desired traits of the parents by crossing. In a screening of 727 accessions, sexual diploid populations were found. Seven sexual diploid lines were developed and their contents of constituents (hypericin, pseudohypericin, hyperforin, adhyperforin, quercetin, quercitrin, isoquercitrin, biapigenin, rutin, and hyperosid) were compared with those of the tetraploid facultatively apomictic cultivar 'Topaz.'. The comparison revealed that both types had the same constituent pattern but, in some cases, considerably different constituent contents. We presume that these differences result from the natural variability among different genotypes which also occurs among tetrap/aid populations. When used as crossing partners in combination breeding, the sexual diploid genotypes from the populations investigated are not expected to cause undesired changes in the constituent pattern of progenies, because the diploids had the same constituent pattern as the common tetraploids. Nevertheless, the breeder should ensure an adequate level of the content of important constituents of crossing partners regardless of their ploidy level or the reproductive pathway. To allow general conclusions, the experiment should be repeated with a greater number of populations.
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