IRRI crossed a tall Indonesian rice with a Chinese dwarf to make high-yield IR8

In 1960 the Ford and Rockefeller Foundations founded the International Rice Research Institute in the Philippines to attack Asia's coming rice shortfall with plant breeding. Its team patiently cross-bred some 10,000 collected varieties. Rice breeding normally yields a 1-2% gain a year, according to geneticist Gurdev Singh Khush, who joined the IR8 team in 1967.

IR8 married a tall high-yielding Indonesian strain, PETA, with a sturdy dwarf from China, DGWG. Khush says rice yields had never before doubled in a single step. IRRI's current head explains that the shortness lets more of the plant's energy go into grain and stops it growing tall and falling over when fertiliser is applied.

Indian farmer Nekkanti Subba Rao sowed IR8 in Andhra Pradesh in 1967 and recalls a harvest he puts at 10 tonnes per hectare, against about 1.5 tonnes before. Seed from 1,000 hectares in his village the next year went across India.

Cross a tall high-yielding strain with a sturdy dwarf, so the plant carries more grain and stays up when fertilised.

Cross-breeding a large collection widened the pool of traits to combine.

Dwarf height solved the lodging problem that stopped tall rice from using fertiliser.

A tall high-yielding parent supplied the yield potential.

Seed multiplication through farmers spread it quickly.

Breeders can get a step change, not a 1-2% annual gain, by combining one trait that raises potential with another that removes the limit on using it.

The BBC reports that IR8's use spread rapidly across Asia, output soared and prices fell, and it is thought to have saved many millions of lives. IRRI's head acknowledges drawbacks: it became the only variety in some areas, cutting biodiversity, it raised fertiliser use and pollution, and its grain was chalky and hardened after cooking. Khush's team spent the next two decades improving taste, pest and disease resistance and growth time. The yield figures are from interviews, and the 10-fold claim is for optimal conditions in some studies.