Полиплоидия и гибридизация в роде Spiraea (Rosaceae): цитогенетические данные по гибриду Spiraea hypericifolia × S. media и его родительским видам в популяциях из Тувы

The polyploidy and hybridization in Spiraea evolution make species identification a complex process. The cytogenetic characteristics of hybrid individuals of Spiraea hypericifolia × S. media, along with those of their parental species, S. hypericifolia L. and S. media Fr. Schmidt, have been the subject of study. The study presents findings of the newly discovered locations of the hybrid S. hypericifolia × S. media in the Republic of Tyva. This is the first study to examine the relative DNA content of S. hypericifolia × S. media individuals. Genomic analysis revealed considerable variability in total genome size, ploidy level and chromosome number among Spiraea from three mixed Tuvinian populations. The results of the cytotyping by chromosome counting and genome size determination by flow cytometry were found to be consistent. Spiraea hypericifolia was found to exhibit a strictly diploid level (2n = 2x = 18). In S. media, three euploid levels were identified for the: diploid (2n = 2x = 18), autotriploid (2n = 3x = 27), autotetraploid (2n = 4x = 36), as well as an aneuploid (2n = 24). Additionally, mixoploidy is occasionally observed in the S. media species. Among the hybrid individuals of S. hypericifolia × S. media, the expected allodiploids (Tselinnoye) and allotetraploids (Turan, Tapsa) were identified. Hypotheses regarding the appearance of autotetraploid of S. media and allodiploid and allotetraploid hybrids of S. hypericifolia × S. media have been proposed. The most probable mechanism of origin of polyploid and hybrid Spiraea species is the disruption of meiosis with the formation of 2n gametes and/or somatic endomitosis. Our findings contribute to understanding of microevolutionary processes within the genus Spiraea. The hybrid S. hypericifolia × S. media has significant potential for use in landscape design and breeding and thus requires comprehensive study.