Chenopodium ucrainicum (Amaranthaceae), a new ‘BB’ genome diploid species: karyological, cytological, and molecular evidence

Abstract In 2020, S. Mosyakin and B. Mandák described a new species from the Chenopodium album aggregate, C. ucrainicum. The description of the species was based mainly on its distinct morphological characters. This study aims to improve our understanding of C. ucrainicum by combining karyological, cytological, molecular, and distribution information. All analyses demonstrated that C. ucrainicum is closely related to C. ficifolium and C. suecicum, the species with the ‘BB’ subgenome. It has the same diploid number of chromosomes (2n = 2x = 18), has very similar genome size (mean ± SD, 1.865 ± 0.026 pg), and is included in the same haplogroup together with polyploid species with the subgenome combination ‘BBDD’. Nevertheless, the haplotype of C. ucrainicum is unique and is not shared with any known closely related species, indicating that the species is very well delimited from other related taxa. A similar result was obtained by RAD-seq data. This finding is particularly significant because species with the ‘BB’ genome played an integral part in the evolution of several allopolyploid taxa, some of which are widespread weeds (C. album s.s., C. berlandieri) or economically important species (C. quinoa). Morphologically, the closest species remains C. suecicum, which is, however, very well genetically differentiated.