Multiple horizontal transfers of nuclear ribosomal genes between phylogenetically distinct grass lineages

Significance A screen of Hordeum (barley) spp. genomes identified several instances of the presence of ribosomal DNA of panicoid origin. The Pooideae and Panicoideae lineages separated from one another around 60 Mya and are sexually incompatible. During the past 1–5 My, at least nine independent transfers of panicoid DNA into Hordeum seem to have occurred, confirming that the transfer of exotic DNA is not an isolated event, at least among the grasses. The supposed rarity of this event in plant genomes more likely reflects technical limitations in its detection rather than it being a genuine biological phenomenon.