Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 12/7/2006
Publication Date: 12/12/2006
Citation: Lulai, E.C. 2006. The Physiology of Suberization: Roles in Resistance to Infection During Wound-Healing and in the Pink Eye Syndrome. Cambridge University Potato Growers Research Association Conference Summary. Program Paper 4.
Technical Abstract: The suberized cells of potato native periderm and wound periderm provide broad and durable protection against infection, dehydration and other problems affecting tuber market quality. Suberization and maintenance of the resulting suberin barrier involve complex processes of great economic importance to all sectors of the potato industry. Cytological analyses have provided a better understanding of the physiology of suberin and suberization; importantly, suberin is composed of two major biopolymers which have been found to play distinct roles in resisting infection. Technologies and information from this cytological research have been applied to the costly problem of pink eye/corky patch (PE/CP), to determine the mechanism of susceptibility to infection and associated rot. The presentation provides insight into the protection provided by the suberin barrier and associated involvement in the PE/CP syndrome. Tuber native periderm consists of three types of cells: (1) phellem, suberized surface cells; (2) phellogen, meristematic cells which divide outwardly to form the phellem; and (3) phelloderm, cells formed inward from the phellogen. Below the phelloderm cells are the cortical parenchyma cells. Maintenance of a healthy native periderm, especially the barrier provided by the suberized cells, is essential for good tuber quality. Rapid healing, i.e. suberization, of wounds incurred during harvest and seed cutting involves the differential accumulation of two structurally distinct suberin biopolymers, suberin poly(phenolic(s)) (SPP) and suberin poly(aliphatics) (SPA), on primary cell walls at the wound surface. The SPP accumulate first in an organized segmented fashion and provide resistance to bacterial, but not fungal infections. After SPP accumulation is complete, SPA accumulate in a non-segmented fashion and provide resistance to fungal infections. This process occurs first on the walls of existing cells, forming the closing layer, and under favorable conditions is followed by the development of a wound periderm which is similar to that of the native periderm described above. Rapid accumulation of both suberin polymers is essential for resistance and varies by genotype. Water vapor loss, causing shrinkage, is controlled by soluble waxes which are embedded within the suberin matrix. Pink eye/corky patch is a serious problem marked by an ephemeral pink coloration, deterioration of skin finish, autofluorescence of cortical cells and susceptibility to a wide range of infections. The PE/CP syndrome has been described as a disease of unknown origin. However, recent research has shown that PE/CP has physiological bases and that the infection related losses are the result of a compromised native periderm that lacks a competent suberin barrier to block infections. The poor skin finish and corky-like surface are consistent with the demise of an active phellogen during growth and the absence of a healthy periderm. Water vapor losses are erratic and elevated indicating concomitant loss of waxes. Results from this research suggest that other unexplained infections and periderm quality problems may be related to undiagnosed PE/CP occurrences.