Disequilibrium and association in barley: Thinking outside the glass

he first verse of ''John Barleycorn,'' a ballad Robert Burns based on an old song of the same name, concludes with ''John Barleycorn should die.''Happily, John Barleycorn does not long lie interred with ''clods upon his head.''Rather, he sprouts to life, produces a head ''arm'd wi'pointed spears,'' and ultimately fills the ''nut brown bowl'' and ''brandy glass'' with liquid joy.The field of barley genetics is also alive and well, as is evident from the report of Rostoks et al. (1) in this issue of PNAS.This article presents compelling evidence that molecular plant breeding, based on naturally occurring allelic diversity, will be a powerful tool for the improvement of self-pollinated crops.