The pink eye syndrome does not impair tuber fresh cut wound-related responses

Authors: Lulai, Edward; Neubauer, Jonathan; Young, Linda; Suttle, Jeffrey

Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/2014
Publication Date: 10/1/2014
Citation: Lulai, E.C., Neubauer, J., Olson, L.L., Suttle, J.C. 2014. The pink eye syndrome does not impair tuber fresh cut wound-related responses. American Journal of Potato Research. 91(5):467-475.

Interpretive Summary: The potato tuber pink eye (PE) syndrome is a costly physiological disorder that results in susceptibility to tuber infection, water vapor loss and associated shrinkage, roughened and cracked tuber surfaces, and various related blemishes and defects. Some of the physiological abnormalities associated with this syndrome have been previously described including the premature death of the phellogen. The phellogen is of critical importance because it is a layer of actively dividing cells which produces the tuber phellem, i.e. skin, and other cells which are part of the native periderm. The tissues collectively known as the native periderm form the surface and subsurface structures that protect the potato tuber. The PE related death of the phellogen results in corruption or deterioration of competency of the protective barrier provided by the native periderm and induction of an aberrant and incomplete healing (suberization ) process within the interior of the tuber without an overt wound signal. The consequences of this unusual internal induction of suberization on the healing of freshly harvested PE afflicted tubers that have been wound damaged are not known. Herein, we determined the effect of the PE syndrome on basic wound-healing processes: reduction of water vapor loss, suberization and induction of the wound-related hormones ABA and JA. PE and control tubers from two different growing areas were analyzed. The results show that the fundamental wound-healing processes involved in control of water vapor loss, suberization and wound-induced increases in ABA and JA are not impacted during the first four days of wound healing. This period is a critical time for initial development of barrier based resistance to infection. However, tissues that are necrotic from PE affliction are adversely impacted; this includes the inability to heal harvest and handling bruised areas of tubers with PE related necrosis. These results are consistent with the earlier hypothesis that PE is a physiological disorder initiated by premature death of the phellogen during tuber growth and bulking. Phellogen death during tuber growth and bulking terminates generation of derivative phellem cells essential to the maintenance of the native periderm at a time when it must expand with increases in tuber size. This resulting loss of native periderm integrity induces an aberrant and ineffective suberization signal that does not repair the corrupted barrier of the native periderm, i.e. the deteriorated phellem (skin), and leaves the tuber susceptible to infection. However, the PE syndrome does not interfere with wound signaling directed to heal tissues cut and excised from non-symptomatic areas of PE afflicted tubers. These results are important because they indicate that the erratic appearance and severity of the PE syndrome does not induce a systemic effect that adversely impacts crucial wound-healing processes in PE tubers.

Technical Abstract: The potato tuber pink eye (PE) syndrome is a costly physiological disorder that results in corruption of the native periderm, susceptibility to infection, water vapor loss and associated shrinkage, roughened and cracked tuber surfaces, and various related blemishes and defects. PE results in aberrant internal suberin deposition without overt induction by a wound, yet little is known of the effect of PE on wound healing. Herein, we determined the effect of the PE syndrome on basic wound-healing processes: reduction of water vapor loss, suberization and induction of the wound-related hormones abscisic acid (ABA) and jasmonic acid (JA). There was no consistent difference in reduction of water vapor loss, accumulation of suberin biopolymers or induction of ABA and JA biosynthesis during wound healing in PE vs control tubers. These results are important because they indicate that the PE syndrome does not induce a systemic effect that adversely impacts these crucial wound-related processes throughout the tuber, including those areas of the tuber that have no detectable PE symptoms.