Which plants should not be planted together?

Some plants hold each other back (allelopathy) or share diseases and pests. Keep apart: onions, garlic and leeks from peas and beans; potatoes from tomatoes (blight), cucumbers, squash and sunflowers; corn from tomatoes; dill from carrots; strawberries from cabbages. Winter rye as a green manure slows small seeds sown after it (carrots, lettuce, beets) — the plan picks another one before them. The plan already keeps bad neighbours in different beds; when there are too few beds, it tells you.