Roguing

Mother Earth News, Sep/Oct 78
Roguing

During the growing season you should regularly examine your seed crops and cull any plants that seem sickly deformed or not true to type. This process - known as roguing - strengthens the strains you're raising byeliminating undesirable traits from the pool of genes that you're working with. You should rogue biennial root vegetables again a second time just prior to winter storage.

Mother Earth News, Sep/Oct 1987
Bring new pleasures and superior plants to your garden
By Nancy Bubel

Another breeder's technique you can adopt is roguing, culling weaker plants before they can affect the seed you want to save. You need to rogue plots of cross-breeding plants before they flower, to prevent them from possibly pollinating the ones whose seed you want to keep.