The International Institute for Environment and Development (IIED) said in a report that the diversity of traditional seed varieties is falling fast and this means valuable traits such as drought and pest resistance could be lost forever.

The report was issued ahead of the World Seed Conference which opens on Tuesday at the United Nations Food and Agriculture Organization in Rome.

"Where farming communities have been able to maintain their traditional varieties, they are already using them to cope with the impacts of climate change," said project leader Krystyna Swiderska of IIED.

"But more commonly, these varieties are being replaced by a smaller range of 'modern' seeds that are heavily promoted by corporations and subsidised by governments."

IIED partner organisations in China, India, Kenya and Peru participated in the research behind the report.

The report said an international tready on the protection of new varieties of plants -- known as UPOV -- protects the profits of private corporations but fails to recognise and protect the rights and knowledge of poor farmers.

"Western governments and the seed industry want to upgrade the UPOV Convention to provide stricter exclusive rights to commercial plant breeders," Swiderska said.

"This will further undermine the rights of farmers and promote the loss of seed diversity that poor communities depend on for their resilience to changing climatic conditions.