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In this assignment we will show how to design a commercial tomato variety which is resistant to whiteflies (Bemisia tabaci). Whiteflies damage the tomato plant and its fruits and are the vectors of many viruses. At the moment viruses are the main thread for commercial tomato growers. Since screening for whitefly resistance is a tedious and laborious procedure, we want to replace the screening during the breeding process with a screening based on molecular markers. However, screenings with living whiteflies are still necessary in the research part when you are looking for sources of resistance in wild tomato plants and when you search for linkage to molecular markers. Also, at the final stage in breeding you need a screening to make sure that you have truly bred a new variety with whitefly prior to commercializing. Resistance against whiteflies in tomato plants is mainly important in field grown varieties because in protected greenhouses natural enemies of whiteflies can be used to control the population build-up of whiteflies (biological control).
Figure: The concept of Marker Assisted Breeding for Research and Application
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