Recent natural hybridization inElymusandCampeiostachysof Triticeae: evidence from morphological, cytological and molecular analyses

Abstract Natural hybrids in Triticeae have been frequently reported from the Qinghai–Tibet plateau, but minor variation in morphological features and homoploid hybridization have made it difficult to identify the origin and genome constitution of hybrids between Elymus and Campeiostachys. Specimens were investigated using morphology, cytogenetics and phylogenetic analyses to uncover the genome constitution and origin of ten putative natural hybrids (SH01-SH10) from the Qinghai–Tibet plateau. SH01, SH02, SH03, SH05 and SH06 (2n = 5x = 35, StStHHY) originated from Campeiostachys breviaristata (2n = 6x = 42, StStHHYY) and Elymus sibiricus (2n = 4x = 28, StStHH); SH04 and SH07 (2n = 5x = 35, StStHHY) originated from C. nutans (2n = 6x = 42, StStHHYY) and E. sibiricus; SH08 (2n = 5x = 35, StStHHY) originated from C. dahurica var. tangutorum (2n = 6x = 42, StStHHYY) and E. sibiricus; and SH09 and SH10 (2n = 4x = 28, StStHH) were the homoploid hybrids of E. sibiricus and an unknown Elymus sp. (2n = 4x = 28, StStHH). Karyotype variations in SH04 and SH07 might originate from the maternal progenitor. Frequent hybridization in the Qinghai–Tibet plateau might result from factors such as genome constitution, pollination habits, overlapping flowering stage, sympatric distribution and unique ecological conditions.