Taxonomic assessment of Allium species from Kazakhstan based on ITS and matK markers

Abstract

Background: As part of nation-wide project to infer the genetic variation of the native flora in Kazakhstan, a study was attempted to assess phylogenetic relationships of endemic and rare Allium species. In total, 20 Allium species were collected in field trips in five different regions of Kazakhstan during 2015-2016. Most species (9) were collected in the southern part of the country along of Karatau mountains, followed by Altai mountains (5) in eastern Kazakhstan. The ITS and matK DNA regions were applied in order to assess the taxonomic relationships among species. The major goal of the study was to assess the taxonomic position of five endemic and rare species from Allium subgenus Reticulatobulbosa collected in Karatau mountains of Southern Kazakhstan. Results: The 20 collected Allium species were assessed using morphological traits and a DNA barcoding approach. The morphological analyses of four different species in subgenus Reticulatobulbosa inferred similarities of A. inconspicuum and A. barszchewskii (both from section Companulata) that were separated from A. oreoscordum and A. oreoprasoides (section Nigrimontana) by several traits, including form of bulbs and leaves, presence of bracts, shape of perianth lobes and style. The Neighbor-Joining method was applied to generate ITS and matK phylogenetic trees for two groups of populations: 1) 20 Allium species collected within the project, and 2) 50 Allium worldwide species. Conclusions: The analyses of nucleotide sequences of ITS and matK robustly confirmed the monophyletic origin of the Allium species. The variability in 20 local Allium species in ITS was 6.6 higher than in matK, therefore the topology of the ITS tree was better resolved. The taxonomy of Allium species largely coincided with a recent classification of this genus. Analyses of both ITS and matK suggest that A. oreoscordum is genetically close to A. oreoprasoides in section Nigrimontana of subgenus Reticulatobulbosa. This result was also confirmed using morphological description of individual plants of four species in subgenus Reticulatobulbosa. The study is another contribution to taxonomy clarification in Allium.