MILAN (Reuters) - Future global food security may be at risk unless greater efforts are made to conserve and use the genetic diversity of cultivated crops and their wild relatives, the United Nations' Food and Agriculture Organisation (FAO) said.

The world's cereals output needs to rise by 1 billion tonnes a year by 2050 to feed a population that is expected to grow by about 40 percent by then from 2005, the FAO said in a report published on Tuesday, reaffirming its earlier forecasts.

Crop biodiversity is a strategic resource for sustainable development and eradication of hunger and it provides insurance against environmental calamities, the agency said in the report on the state of the world's plant genetic resources for food and agriculture.

Fast-growing, high-yield new crop varieties resistant to heat, drought, salinity, pests and diseases -- crucial to ensure food security in the face of climate change -- can be developed using genetic information held in certain plants, the FAO said.

New seed varieties have accounted for 50 percent of the rise in crop yields in recent years with irrigation and fertilisers accounting for the rest of the growth, it said.

"There are thousands of crop wild relatives that still need to be collected, studied and documented because they hold genetic secrets that enable them to resist heat, droughts, salinity, floods and pests," FAO Director-General Jacques Diouf said.

With an industrial focus on output of a few major crops, 75 percent of crop diversity was lost between 1900 and 2000 and up to 22 percent of the wild relatives of peanut, potato and beans will disappear by 2055, hit by a changing climate, the FAO said.

More funds are needed to preserve crop biodiversity and improve collection and use of its resources, it said.