Other pages about bruise defects:
A very common type of bruising is skinning (Picture) which involves a tearing of the periderm resulting from impacts with blunt objects or sides of harvest and piling equipment. Skinned areas turn dark after a short time making tuber appearance unacceptable and as mentioned earlier, pathogens can enter through these abrasions and water can be lost from the tuber as well. This type of abrasion (scrapes, rubs, scuffs), sometimes called feathering, has been the principle focus in understanding the wound healing process at the tissue and cellular level (Lulai, 2002). Cultivars differ in these characteristics (Lulai and Orr, 1993). The principle factor affecting skinning, besides collisions, is the maturity of the tuber at harvest and this relates to both susceptibility to skinning (that is their level of skin set) and to their ability to heal the abrasion (Lulai and Freeman, 2001). Skinning is a result of poor adherence of the skin to the parenchyma cells below it and therefore the higher shear strength of the skin the less likelihood of skinning. Tuber maturation and skin set are directly related to time after vine death. Chemical or mechanical vine desiccation will start the process of skin set resulting in greater resistance to skin shear and to skinning (Pavlista, 2002).
Lulai, E.C. 2002. The roles of phellem (skin) tensile-related fractures and phellogen shear-related fractures in susceptibility to tuber-skinning injury and skin-set development. Amer J Potato Res 79:241-248.
Lulai, E.C. and Freeman, T.P. 2001. The importance of phellogen cells and their structural characteristics in susceptibility and resistance to excoriation in immature and mature potato tubers (Solanum tuberosum L.) periderm. Annals Bot 88:555-561.
Lulai, E.C. and Orr, P.H. 1993. Determining the feasibility of measuring genotypic differences in skin-set. Amer Potato J 70:599-609.
Pavlista, A.D. 2002. Skin set evaluation by skin shear measurements. Amer J Potato Res 79:301-307.