Wound-healing responses varied across different cell layers of potato tubers (P-28)

Wounding of potato tubers during harvest and postharvest handling can lead to losses of tuber integrity and market qualities. Rapid wound-healing (WH) of potato tubers is essential to protect tuber qualities at postharvest storage and ensure higher market values. In general, natural WH response of potato tubers involves formation of suberin barrier in open cut surface and development of secondary skin, if tubers are allowed to heal under conducive conditions. Tuber tissues are composed of different cell layers with varying cellular structure and metabolic composition, which might influence their overall WH rate. Therefore, the objective of this research is to investigate formation of suberin barrier and profile of protective metabolic compounds across different cell layers of potato tubers. WH responses of cvs. Russet Burbank and Dakota Russet were investigated using three different cell layers of tubers: i) outer layer or cortex near skin, ii) middle layer or outer medula, and ii) core or inner medula. An mechanical wounding model, where cylinder of tuber flesh tissue excise laterally from each tuber, was employed, and discs (3 mm width and 11 mm diameter) were collected separately from each cell layer and treated with 2-(N-morpholino)ethanesulfonic acid (MES) buffer for 1 hour. Then discs were kept in a controlled environment chamber (20°C and 95% relative humidity) to allow WH and tissues from different cell layers were collected separately at 0, 2, 4, 6, and 8 days after wounding for microscopical and biochemical analysis. Microscopical observation of the suberin polyphenolic accumulation in wounded cell layer indicated that core tissues (inner medula) healed faster, while tissues from cortex region healed slower. Results of the biochemical analyses revealed that antioxidant enzymes and profile of metabolites such as phenolics and flavonoids varied significantly among three cell layers and might contributed to their different WH responses.