Genomic Composition of the Artificial Hybrid ×Trititrigia cziczinii (Hordeeae, Poaceae) and Related Taxa According to Molecular Phylogenetic Data.

×Trititrigia cziczinii Tzvelev is a promising crop developed through distant hybridization between Elytrigia intermedia (Host) Nevski (=Thinopyrum intermedium (Host) Barkworth & D.R. Dewey) and Triticum aestivum L., followed by backcrossing with wheat. This study elucidates the genomic composition of this hybrid and its parental taxa using molecular phylogenetic analysis of nuclear (ITS, ETS) and chloroplast (trnK-rps16, ndhF) DNA markers, complemented by Next-Generation Sequencing (NGS) of the 18S-ITS1-5.8S rDNA region. Results from Sanger sequencing revealed that the primary nuclear ribosomal DNA (rDNA) of the hybrid originates from Triticum aestivum; a finding strongly supported by both Bayesian inference and Maximum Likelihood analyses. Chloroplast DNA data unequivocally indicate maternal inheritance from T. aestivum. In contrast, ETS sequence analysis showed phylogenetic affinity to Elytrigia intermedia, suggesting complex genomic reorganization or chimeric sequence formation in the hybrid. NGS data corroborate the dominance of T. aestivum-like ribotypes in the hybrid's rDNA pool, with only a minor fraction identical to the main ribotype of E. intermedia. Genetic structure analysis further revealed geographic heterogeneity in the genomic composition of E. intermedia populations. The predominance of the wheat genome in ×T. cziczinii is likely a consequence of stabilizing backcrosses and illustrates a case of rDNA elimination from one parental genome during hybridization. This research underscores the complex genomic dynamics in artificial hybrids and the utility of multi-marker phylogenetic approaches for clarifying their origins.