On the eve of the first meeting of the signatory states, the UN organisation has proclaimed the treaty as a "historic landmark in North-South cooperation".
The treaty is a legally binding instrument negotiated by FAOs member states, and came into force in June 2004 as the culmination of a long process that began in the 1970s.
Its purpose is to safeguard the genetic diversity of crops.
The FAO says that throughout history, humans have used some 10,000 plant species for food. But today, our diet is based on just over 100 species, due to the introduction of a small number of modern and enormously uniform commercial varieties.
The governing body of the treaty will hold its first meeting in Madrid on 12 to 16 June, attended by all the countries that have ratified the treaty, now numbering 100 with the recent accession of Iran.
The meeting will lay down the procedures for implementation and other key aspects, such as a financial strategy, access to plant genetic resources and the sharing of benefits deriving from their use.
"This international agreement not only guarantees the conservation and sustainable use of plant genetic resources, but also the fair and equitable sharing of benefits arising out of their use, including any monetary benefits of commercialisation," said Jose Esquinas Alcazar, secretary of the FAO commission on genetic resources for food and agriculture.
"For the first time, farmers rights are formally acknowledged, on the understanding that it is the traditional small-holders in every part in the world who have made the greatest contribution to developing agricultural biological diversity over the millennia, and are still its main custodians."
The FAO claims that genetic resources are the raw materials farmers and scientists need to develop new varieties to address potential challenges such as plant pests and climate change.
The treaty will create a multilateral system of access to plant genetic resources. This system applies to a list of 64 plant species, selected on the basis of food security and interdependence criteria, including wheat, rice, potatoes and maize, which are staple components in the diet of a large proportion of the worlds population.
"No country is self-sufficient in genetic resources in agriculture," said Esquinas. "FAO has calculated that countries are about 70 per cent interdependent.
"Every country depends on the genetic diversity of plants in other countries and regions to guarantee food security for their own people."