A pest which ruins a third of Brazil's oranges each year could soon be eliminated, thanks to the genome sequencing. According to Andrew Simpson of the Ludwig Institute for Cancer Research in Sao Paulo, Brazil, the bacterium, Xyella fastidiosa is the first plant pest genome to be completely sequenced. This bacterium causes the devastating disease called citrus variegated chlorosis, which affects 80 per cent of the orange trees around Sao Paulo, which is the world's premier orange juice producing region. "The bacteria block up the xylem, the channel which transports sap from the roots to the periphery of the plant, and this means the oranges have no juice,' he says. At present, farmers use insecticides to kill the leafhoppers that spread the bacterium.

Simpson and other researchers have discovered 67 genes that enable the bacterium to scavenge and hoard iron. "It looks like it's dependent on iron for survival,' he says. Simpson adds that it might be possible to genetically alter orange trees to resist the disease ( Nature , Vol 406, p151).