Seed lipid profiles of perennial ryegrass: Global patterns and differentiation of ryegrass cultivars and <i>Epichloë</i> endophytes

Abstract Background Forage perennial ryegrass ( Lolium perenne L.) has been extensively researched regarding vegetative growth and quality, with its seed being relatively unexplored. The declining viability of Epichloë fungal endophytes in ryegrass seed during storage underscores the need for dedicated biochemical research. Methods We conducted a lipidomic investigation of seeds from five fungal endophyte–perennial ryegrass associations: tetraploid ryegrass cultivars KLp1102, KLp1103 and KLp903 infected with the endophyte strain AR501 and cultivar KLp1102 independently infected with strain AR1 or AR37. Results Storage lipids in perennial ryegrass seeds were predominantly triacylglycerols (TGs) containing C18:2, C18:1, C18:3 and C16:0 fatty acyl chains. Notably, TGs and diacylglycerols (DGs) containing medium‐chain fatty acids (C8:0, C12:0 and C14:0) showed differential accumulations among the seeds of the three cultivars infected with AR501, as well as among the seeds of KLp1102 infected with AR1, AR37 and AR501. The distinct responses of typical storage glycerolipids (C18 and C16 fatty acyl chains) and medium‐chain glycerolipids (C8, C12 and C14) among KLp1102‐AR1, KLp1102‐AR37 and KLp1102‐AR501 samples highlighted the influence of endophyte strains on host biochemistry. These findings suggest that medium‐chain TGs and DGs play critical roles in maintaining effective ryegrass–endophyte associations. Conclusions This study identifies numerous structural and signalling lipid species, providing a foundational understanding of lipid composition in perennial ryegrass seed. The results offer new opportunities to investigate the mechanisms underlying endophyte viability during storage and to elucidate the genetic regulation of differentially accumulated signalling lipids across different ryegrass cultivars.