Other pages about bruise defects:
The third type of external bruise is shatter which is the splitting of the skin caused by hard impacts such as drops, greater than six inches, during the moving and piling operation. Shatter bruise appears as small cracks radiating from the point of impact and can also be caused be some tuber diseases such as ring rot (Picture). Over-hydrated tubers, often harvested from wet soils, are especially susceptible to shatter; skin shattering is directly proportional to tuber hydration. Harvesting and handling tubers below 50 F allow tubers to shattered more easily. Tubers with high specific gravity or greater dry matter content also seem to be more susceptible to shatter. Potato tubers with this bruise are readily prone to tuber early blight as well as to dry rot and wet rot.
Chase, R.W. and Silva, G.H. 1987. Potato Bruising. Mich. St. Univ. Coop. Ext. Bull. E-2074.