Biologists have discovered how the rice plant's immune system is triggered by disease, in a discovery that could boost crop yields and lead to more disease-resistant types of rice. Rice is central to the food security of more than half the world's population in many of the poorest countries. But bacterial leaf blight can destroy up to 80 per cent of a crop in some countries if it develops early.

Researchers studying bacterial leaf blight have found that rice detects a molecule called RaxX secreted by the bacteria.

"We've discovered a new molecule that's never been seen before," said Dr Benjamin Schwessinger, from The Australian National University (ANU).

"We've realised that this type of molecule plays an important role in the immune response of rice plants.

"It will now be much easier to develop containment strategies against the disease and breed more robust rice plants."

The research could help the fight against similar diseases in other crops, and may even give insights into human health, as the chemistry is similar to that of HIV entering human cells.

Some strains of rice are naturally resistant to the disease, which gave the international team a clue to what was going on.

The team discovered that the rice plant's XA21 immune system is triggered when the RaxX molecule is secreted by the leaf blight bacterium Xanthomonas oryzae pv. oryzae (Xoo).

The team generated mutants of Xoo that did not produce RaxX and tested whether they triggered the rice immune response, which allowed them to isolate the Xoo gene that was creating the RaxX molecule.