Continuing addition to the gene-pool of theFestuca rubra aggregate (Poaceae:Poeae)

The chance backcrossing to hexaploidFestuca rubra of a natural pentaploid hybridFestuca rubra ·Vulpia fasciculata to produce a hexaploid plant is described. The hexaploid derivative, unlike the pentaploid hybrid, shows a reasonable degree of fertility and is morphologically very close to normalFestuca rubra. Its existence provides a mechanism for the continued introgression ofVulpia fasciculata intoFestuca rubra, so increasing the variability of the latter. It also shows that pairing betweenFestuca rubra andVulpia fasciculata chromosomes must have taken place either in the pentaploid hybrid or in its hexaploid derivative. A possibly similar pattern of introgression involvingVulpia bromoides is also described.