This injury occurs as the result of low oxygen levels in the interior of the tuber and is relatively easy to diagnose. The center of affected tubers is black to blue black, in an irregular pattern, and the border of the discolored area is usually very distinct. Darkened areas of the tuber are usually fairly firm, in contrast to those of tubers affected by Pythium leak, which are spongy. Affected tissues do not smell, and shrinking of the tissue may result in the formation of a cavity in the center of the tuber. Blackheart develops when tubers are held in a low–oxygen environment or when gas diffusion through the tubers is slowed because of extremely cold (32° F) or warm (96°–104° F) temperatures. This condition can also develop in the field when soils are flooded or in poorly aerated storages. Because seed–piece size is effectively reduced by the death of affected tissues, plant stand and vigor are likely to be reduced.