The convention, which aims to ensure that plant genetic resources can be preserved and made available for research and plant breeding, will come into force after it is ratified by at least 40 states.

"This new legally binding international agreement...provides a framework to ensure access to plant genetic resources, and to related knowledge, technologies, and internationally agreed funding," FAO, holding its biennial conference, said in a statement.

After years of anguished debate pitting poor countries and environmentalists against multinational corporations and wealthier nations, the United States agreed for the first time in July to mandatory payments by plant breeders developing new crop varieties in return for access to public seed banks.

The seed banks lend out crop seeds, enabling research into new varieties of plants to increase resistance to disease and counter the impact of global warming.

In turn, this helps alleviate hunger in poorer nations.

FAO Director-General Jacques Diouf said the approval of the framework ended years of tortuous negotiations and created an internationally accepted mechanism to protect agricultural biodiversity.

"The approval by the FAO conference of this International Convention on Plant Genetic Resources for Food and Agriculture is a milestone in international cooperation," Diouf said.

CROP DIVERSITY NEEDED TO COMBAT HUNGER

Agricultural biodiversity must be saved in order to guarantee global food security as the population grows and the planet warms up, plant geneticists say.

Plant varieties are becoming extinct at an unprecedented rate, according to the Italy-based International Plant Genetic Resources Institute (IPGRI).

IPGRI, an international body dedicated to the conservation and use of plant genetic resources for food and agriculture, estimates that every year more than 15 million hectares of tropical forest are destroyed. It says eight percent of plant species run the risk of extinction in the next 25 years.

Over the past 50 years high-yielding uniform varieties of crops have taken the place of thousands of local varieties across large productive areas.

Scientists will have to develop plant varieties resistant to drought, salinity and disease in order to increase the rate of food production to keep up with the expanding population, plant geneticists say.