When soils are too acidic, aluminum that is locked up in clay minerals dissolves into the soil as toxic, electrically charged particles called ions, making it hard for most plants to grow.

In fact, aluminum toxicity in acidic soils limits crop production in as much as half the world's arable land, mostly in developing countries in Africa, Asia and South America.

Now, Cornell researchers have cloned a novel aluminum-tolerant gene in sorghum and expect to have new genetically-engineered aluminum-tolerant sorghum lines by next year.

The research, to be published in the September issue of Nature Genetics, provides insights into how specialized proteins in the root tips of some cultivars of sorghum and such related species as wheat and maize can boost aluminum tolerance in crops.

Cornell's research shows that in aluminum-tolerant sorghum varieties, special proteins in the root tip release citric acid into the soil in response to aluminum exposure. Citric acid binds aluminum ions very effectively, preventing the toxic metal from entering the roots.

Sorghum is an important food crop in Africa, Central America and South Asia and is the world's fifth most important cereal crop.