Provided is a method for obtaining DNA from a plant by collecting the root border cells from a growing root and extracting DNA from the root border cells. Preferably, the root border cells are contained in the root exudate of the growing root, which is growing in a medium, for example, water, tissue culture medium, or soil. Suitably, the root is part of a germinating seed, or the root of a seedling, or the adventitious root of a tissue culture plant or plant part.