THREE-quarters of the world's crop biodiversity has been irrevocably lost since 1900.

And the steady decline in genetic diversity in plants has placed extreme pressure on the world's ability to feed its population.

That's according to the International Treaty on Plant Genetic Resources for Food and Agriculture secretary Shakeel Bhatti, who addressed a Rural Press Club of Victoria breakfast in Melbourne on Monday.

Dr Bhatti said gene banks had been set up around the world, but sharing of the genetic material had been problematic since the 1970s.

Governments reacted to smooth tensions, culminating in the legally binding IT-PGRFA in 2001, auspiced by the Food and Agriculture Organisation.

The treaty allows gene banks, research institutes, farmers and agricultural industries to pool and share their genetic material.

Australia has been a strong supporter among the 127 countries that have become signatories for the treaty.

Dr Bhatti said the treaty allowed free access to more than 1.5 million samples of genetic material.

He said the gene pool included the world's 64 most important crops. The loss of plant diversity had been profound, Dr Bhatti said.

"In China, we have seen during the last 60 years about 90 per cent of wheat varieties lost," he said.

"In India, there has been the loss of about 90 per cent of rice varieties.

"While in the past we were relying on 10,000 plant species for food production, today, we barely have 150 species, of which 12 provide about 80 per cent of nutrients and four - wheat, rice, maize and potatoes - provide half the caloric intake."

Dr Bhatti said sharing of the gene pool allowed countries to develop crops better able to adapt to environmental changes.

He said Australia had much to gain from using the treaty, as productivity in the grains sector had declined in recent years.

The recent Australian breakthrough in developing a salt-tolerant durum wheat was made possible by accessing germplasm from international gene banks, Dr Bhatti said.

He said that breakthrough was well-received globally because salinity affected 20 per cent of the world's soils.

"In the US, it accounts for about $12 billion," he said.