Anatomy of 'Green Revolution' unraveled

Anatomy of 'Green Revolution' unraveled

Agence France-Presse, Paris

DNA engineers say they have sequenced the gene that kicked off the "Green Revolution," the breakthrough in rice growing 35 years ago that saved tens of millions of Asians from likely starvation.

The superstar plant, devised by the International Rice Research Institute (IRRI) was a variety called IR8, which dramatically doubled grain yield at a time when populations in China, India, Indonesia and elsewhere was growing alarmingly.

IR8 was a semi-dwarf variety that was a cross between a tall Indonesian variety called Peta, which was vigorous and resistant to insects and disease, and Dee-geo-woo-gen, a high-yield but short-stalked strain from Taiwan.

IR8 worked well because it efficiently converted nitrogen fertiliser into grain, yet did not become reedy and long-stalked and thus topple over in wind and rain as it grew.

The reason, says a team of researchers led by Motoyuki Ashikari of Japan's Nagoya University, is a mutation in IR8 of a key gene called sd1 that controls plant height.

The sd1 gene controls an enzyme that in turn helps to produce growth-stimulant hormone called gibberellin.

But in IR8 and a dwarf variety of super-wheat called Rht that is another product of the Green Revolution, a key sequence of sd1 has been deleted.

The result: the gibberellin is in effect switched off, and the plant stalk remains the same height, despite the stimulus provided by the fertiliser.

This discovery could be of major help in further boosting yields of rice, the world's most important crop, and other important crops, Ashikari reports in Thursday's issue of Nature, the British science weekly.

The genetic code of rice, called the gnome, was published earlier this month, a feat that should enable biotechnologists to identify plant characteristics relatively easily in order to create new strains.