Known as TuMV, the virus is a member of the Potyvirus family - the biggest family of viruses that attack plants. It is spread by aphids, and results in leaves that are streaked, flecked or ringed with light and dark shades of green. According to the USDA, the virus is widely prevalent in Arizona, Arkansas, Delaware, Georgia, Kentucky, Massachusetts, Minnesota, Ohio, Pennsylvania, Virginia and Wisconsin. The research, published this month in the Journal of General Virology, could not only help alleviate this threat in commercially cultivated crops but is also expected to have implications for breeders of other plants, too. The researchers from Warwick HRI, part of the University of Warwick, examined a number of genes that have a hand to play in making the Brassica rapa line RLR22 resistant to eight diverse TuMV isolates. They found that some genes mean that plants will kill off individual cells if they become infected with a virus. This means that the infection is kept limited to a small area. In the case of other genes, the effect is a restriction of movement of the virus from leaf to leaf is restricted, stopping its spread. Finally, they identified some genes that seem to prevent any virus replication in the plant. Dr John Walsh, who lead the research team, said: "By breeding these genes into commercial varieties of the crop, using conventional techniques, breeders can protect them from attack." But he added that the most important finding was the broad-spectrum resistance given by a number of genes. "This means we potentially have the means to develop brassicas, such as broccoli, that will be robust enough to prevent the virus mutating to overcome the resistance." The research was funded by the Biotechnology and Biological Sciences Research Council (BBSRC), the UK's Department of the Environment, Food and Rural Affairs (DEFRA), the European Union and Agriculture and Agri-Food Canada. The team has received further funding from the BBSRC's Crop Science Initiative to continue work in this field. Reference: Journal of General Virology 88, 3177-3186 (November 2007) "Genetic control of broad-spectrum resistance to Turnip mosaic virus (TuMV) in Brassica rapa (Chinese cabbage)" Authors: Rusholme, RL, Higgins, EE, Walsh, JA. & Lydiate, DJ
