It is Australia's second largest grain crop and one of the world's earliest farmed cereals, but just how barley became domesticated has long puzzled researchers.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 4 minutes 5 seconds 4 m 5 s Emeritus Professor Geoff Fincher says a group of international researchers has unlocked the genetic key to reveal how the humble barley became domesticated ( Tiarne Cook ) Download 1.9 MB

Now an international team of researchers has solved that puzzle.

They have identified a genetic change which explains how wild barley shifted from dropping its grain to the ground at maturity to the grain staying in the ear.

Emeritus Professor Geoff Fincher, at the University of Adelaide's School of Agriculture Food and Wine, said their finding marks a crucial point in the domestication of barley.

"It's just a matter of interest really to think about how our ancestors, our ancient famers from 10,000 years ago, how amazed they must have been to see out in the middle of their field, a barley variety or a barley line which was holding onto its grain," he said.

"They immediately realised, that this was a way they could harvest large amounts of grain and cultivate barley."

Professor Fincher said they discovered two genes, Btr1 and Btr2, involved in the grain dispersal of wild barley at maturity.

"The group found an ancient gene which caused a brittle rachis or a brittle head on barley plants and it meant when the grain ripened and dried, any force like wind, would cause it to drop off, important for dispersal and the survival of the species."

But 10,000 years ago in the area now known as Syria, Israel, and Jordan, a spontaneous mutation occurred which changed the rachis from being brittle, to non brittle.

"What this means was the grain, when it matured, didn't actually fall off the head or the spike and it remained there until all the grains had matured and it meant farmers could harvest the grain more easily," Professor Fincher said.

He said the principal can be applied to different crops like wheat.

"There's terrific potential in some of these wild relatives of wheat and barley and the wild ancestors of these modern lines, because during that domestication process in many cases very useful genes have been left behind as farmers pick one particular line," he said.

"So things like disease resistance genes might have been left behind during the domestication process and there are groups around the world looking for these beneficial disease resistance genes."

The findings have been published in the Journal Cell.