In the early 1970s Asia's rice farmers faced ruin. The brown planthopper, an insect up till then found mostly in Japan, began to appear across the region. It fed on young plants and transmitted grassy stunt virus, causing crops to shrivel and brown. As it swept through Asia's paddy fields, yields crashed. By the end of the decade it had caused damage costing over $3oom-more than $1 billion in today's money. Scientists raced to find a solution. They screened over 6,000 samples of rice and its wild relatives until they found a unique sample from central India of a wild species called Oryza nivara that was resistant to the virus. By crossing it with domesticated rice strains, plant-breeders transferred the resistant genes into a new variety. Today, millions of farmers across Asia grow rice derived from such crosses. "Crop wild relatives"-the wild ancestors of cultivated plants-are a valuable weapon in the fight against hunger. Together with varieties used by traditional farmers, they contain a wealth of genetic diversity. Yet they are under-researched and under-collected. With their survival threatened by population growth and environmental damage, the race is on to find them before it is too late.
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