Once again we will turn briefly to the subject of law enforcement, although this time we are specifically concerned with how molecular markers can provide evidence in legal cases that are directly relevant to agricultural concerns. One way is through the quality control of food as part of an ongoing programme to decrease the likelihood of future epidemics. The 1980s saw the start of an outbreak of bovine spongiform encephalopathy (BSE) in the UK. Also known as mad cow disease, this is a disease that affects the brain and spinal cord of cattle, and can apparently be transmitted to humans in the form of a variant of CreutzfeldtJakob disease (CJD). The disease can be spread between cattle if they are fed contaminated meat and bone meal, and for this reason the European Union introduced severe restrictions on the incorporation of animal protein into farm animal food. For the most part, processed animal proteins cannot be fed to animals that are destined to become food themselves, the exception to this being that fishmeal can be fed to non-ruminant animals. There is a risk, however, that fishmeal can be either contaminated or illegally supplemented with bones or tissue from other vertebrates. Fishmeal can now be efficiently checked for the presence of meat from mammals or poultry by using a set of species-specific primers that amplify a region of the 12s ribosomal RNA mitochondrial gene. The specificity of these primers means that they will amplify a product only if DNA from a particular species is present, and therefore diagnosis can be made simply on the basis of whether bands are present or absent. This technique can be used to identify mammalian or chicken DNA at concentrations as low as 0.25 per cent (Bellagamba et al., 2003).
A second link between molecular markers, agriculture and law enforcement comes from the identification of different plant varieties. Registered trademarks often protect the economic rights of plant breeders who have successfully developed a novel marketable strain of a particular crop. In one case, charges were brought against some farmers in Italy who were believed to be unlawfully growing an Italian patented breed of strawberry known as Marmolada®, a variety that is sought after in some areas because of its tolerance to cold. The farmers in question denied that they were growing Marmolada® and the case could not be solved without unambiguous identification of the plants. Because the commercial production of strawberries involves micropropagation, all copies of a particular variety are genetically identical and therefore it was necessary to demonstrate that the genotypes of the known and suspected Marmolada® plants matched each other. This was accomplished with RAPD markers, which revealed Marmolada® -specific genotypes in 13 out of the 31 plants that had been genotyped. All 13 of the plants that genetically matched the Marmolada® strawberries turned out to be the plants that had come from the farm that was under investigation. The remaining 18 plants constituted a negative control that the court had included without the knowledge of the laboratory staff. On the basis of the RAPD profiles, the court concluded that the farmers had unlawfully commercialized a patented variety of strawberry (Congui et al., 2000).
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