Abstract:The Elymus grasses, known for their strong ecological adaptability, are a primary genetic resource for improving the quality of grasslands in the Qinghai-Tibet Plateau. This study focuses on the diversity of inflorescence branching types among Elymus species in alpine regions. It examines 76 Elymus inflorescence branching germplasm resources from different areas of the Qinghai-Tibet Plateau, measuring and analyzing the related phenotypic characteristics. The findings are as follows: (1)There is significant variation among the 76 materials, with a high diversity index across 24 traits, averaging an H′ index of 5.19. (2)In this survey, Elymus inflorescences showed only primary branching, averaging 7.03 branches per inflorescence, with a mean branching rate of 33.90%. Branches typically occur in the middle to lower part of the main inflorescence axis, with the highest variation (98.14%) in the starting point of branching on the axis. (3)Correlation analysis revealed highly significant positive correlations between the number of branches and branch rate, branch width, total length of branched spike, and total length of inflorescence. Branch rate was highly significantly positive correlated with branch width and the endpoint of the branch. The total length of the branched spike was significantly positive correlated with the total length of the inflorescence and the number of seeds on the branched spike. (4)Principal component analysis identified 4 main components, accounting for 84% of the cumulative contribution rate. The first principal component (36%) reflects the variability related to the quantity and length of branches. The second principal component (30%) reflects seed weight and distribution characteristics. The third principal component (12%)reflects variations in branch occurrence sites and overall inflorescence length. The forth principal component (6%) reflects the ratio of branch axes to inflorescence length and seed number weight density. (5)Cluster analysis categorized the 76 Elymus inflorescence branching germplasm resources into three types: less branching, more branching and balanced branching. With further phylogenetic relationships analysis based on inflorescence phenotypic characteristics categorized the 76 Elymus inflorescence branching germplasm resources into nine types: high branching, dense branching, long sparse branching, balanced branching, heavy-seeded high-yielding, medium branching, sparse branching, short low-yielding, and uniformly stable-yielding. These nine categories primarily reflect the characteristics of branching and seed yield, providing a basis for further selection of ideal inflorescence types.In summary, the 76 Elymus inflorescence branching germplasm resources show high diversity and phenotypic variation. The occurrence of branching alters the pattern of seed yield, providing a theoretical foundation for improving seed yield of Elymus grasses in alpine regions.