Scientists are developing new flood and drought-prone rice varieties to combat the threat of global warming to Asia's food staple but more work is needed, the International Rice Research Institute (IRRI) said.

The institute needs $25 million over the next 5 to 7 years to study the impact of rising temperatures, higher concentrations of greenhouse gases and greater extremes of droughts and floods on rice production.

The institute was developing rice lines that were tolerant of drought, and had just begun research on rice that could withstand high temperatures.

It is also helping with work on genetically modified Vitamin A enriched rice or "golden rice".