Unveiling the genetic determinants of germination efficiency in common bermudagrass: A genome-wide association study

Common bermudagrass [Cynodon dactylon (L.) Pers.] is an economically and ecologically important warm-season perennial species widely used for turf, forage, and soil conservation and remediation. Seeding offers economic and practical advantages over vegetative propagation for establishing common bermudagrass. However, the adoption of seeded cultivars is limited by slow germination speed and low germination rates. The genetic basis behind these traits in common bermudagrass remains elusive. Accordingly, the objective of this study was to evaluate the genetic and phenotypic variation and identify genetic loci associated with seed germination-related traits in a diverse common bermudagrass panel. A diverse panel of 216 genotypes was formed for a genome-wide association study (GWAS). Seeds for each genotype of the panel were collected in both 2022 and 2023, and germination tests for each year were conducted separately in a randomized complete block design with three replications (100 seeds per replicate) in petri plates inside a growth chamber. The germination process was phenotyped by counting germinated seeds every 3 days from the beginning to determine the germination rate and estimate total germination percentage over a 21-day period. The panel underwent genotype-by-sequencing, and 21,810 high-quality single-nucleotide polymorphisms (SNPs) were retained for GWAS analysis. GWAS indicated that 52 unique SNPs were associated with the seed germination traits, of which six were consistent over the 2 years. Twenty candidate genes linked to the consistent SNPs were identified to be involved in seed germination. These findings add valuable information on genetic mechanisms for seed germination and its rapidness, and provide a foundation for developing breeder-friendly markers to improve seed germination in the species.