Analysis wheat wild relatives Thinopyrum intermedium and Roegneria kamoji genomes reveal different polyploid evolution paths.

Many wild relatives of wheat in the Triticeae tribe provide important genetic resources for crop improvement, but their complex, polyploid genomes shaped by hybridization remain poorly understood. Here, we assemble and analyze the genomes of Thinopyrum intermedium and Roegneria kamoji, two species commonly used in wheat hybridization. We show that Th. intermedium contains genomic contributions from Pseudoroegneria (St), Dasypyrum (V), and Aegilops (J), while R. kamoji contains subgenomes related to Pseudoroegneria (St), Dasypyrum (V-related "Y"), and Hordeum (H). Phylogenomic evidence indicates that both species underwent independent polyploidization events, with Pseudoroegneria serving as the original maternal donor. R. kamoji likely evolved from tetraploid Roegneria. We also identify two Fhb7 homologs in the St and H subgenomes of R. kamoji that enhance Fusarium head blight resistance in a dosage-dependent manner. These findings refine the understanding of Triticeae polyploid evolution and offer valuable genomic resources for wheat improvement and forage breeding.