Befuddling the enemy
A genetically engineered strain of cereal has been developed that is resistant to rice tungro disease. If this viral infection breaks out, it can destroy nearly 90 per cent of a crop. A team of researchers led by Roger Beachy of the International Laboratory for Tropical Agricultural Biotechnology at the Scripps Research Institute, California, USA, has developed the strain. Two viruses are required to transmit rice tungro disease from plant to plant, and the epidemic only occurs when plagues of leaf hoppers are around. The symptoms of the disease are caused by the DNA-containing rice tungro bacciliform virus. But unless the RNA-containing rice tungro spherical virus is present, the leaf hoppers cannot produce a protein, which they need to pick up the infection and pass it on. The rice plants have been equipped with copies of viral genes that allow them to produce the same proteins the viruses do. The genes make a protein in a virus that helps the virus to reproduce. Rice plants containing these viral genes show resistance to tungro. When the viruses fight with viral proteins, they stop reproducing ( New Scientist , Vol 155, No 2100).