Abstract:The St and E are two important basic genomes in the perennial tribe Triticeae (Poaceae). They exist in many perennial species and are very closely related to the A, B and D genomes of bread wheat (Triticum aestivum L.). Genomic Southern hybridization and genomic in situ hybridization (GISH) were used to analyze the genomic relationships between the two genomes (St and E) and the three basic genomes (A, B and D) of T. aestivum. The semi-quantitative analysis of the Southern hybridization suggested that both St and E genomes are most closely related to the D genome, then the A genome, and relatively distant to the B genome. GISH analysis using St and E genomic DNA as probes further confirmed the conclusion. St and E are the two basic genomes of Thinopyrum ponticum (StStEeEbEx) and Th. intermedium (StEeEb), two perennial species successfully used in wheat improvement. Therefore, this paper provides a possible answer as to why most of the spontaneous wheat-Thinopyrum translocations and substitutions usually happen in the D genome, some in the A genome and rarely in the B genome. This would develop further use of alien species for wheat improvement, especially those containing St or E in their genome components.