Rapid Curing as a Means of Minimizing Postharvest Losses In Early Potatoes

Early season potatoes (Solanum tuberosum L.) are harvested before adequate development of the periderm (skin-set), making them susceptible to wounding during harvesting and postharvest handling. The objective of this research was to evaluate ‘rapid curing’, where tubers are stored for short periods under higher temperatures and relative humidity (RH) than standard curing conditions, as a means of expediting wound-healing in two tablestock potato cultivars. ‘Fabula’ and ‘Red LaSoda’ potatoes were grown during two spring seasons following commercial practices. Plant vines were killed at horticultural maturity to promote skin-set; however, ‘Fabula’ has inherent seed dormancy that results in delayed periderm maturation. Tubers were hand-harvested 3 weeks after vine kill. To accurately document wound-healing, periderm and underlying cortical tissue (20-mm diameter, 2-mm deep) was carefully excised from the equatorial region of each tuber (n=50). Half of the tubers were placed in rapid curing conditions of 20ºC, 90-95% RH (T-20) for 5 d, then transferred to simulated commercial storage conditions (10ºC, 80-85% RH) for 9 d. The other half were stored continuously at 10ºC, 80-85% RH (T-10). Fresh weight loss, dry matter content and histochemical analyses were conducted at 0, 5, and 14 d; the depth of suberized cell layers on the wound periderm measured the extent of wound-healing. ‘Fabula’ T-20 tubers had a significantly thicker suberized layer (16.5 µm) than T-10 (12.5 µm) after 5 d. After an additional 9 d at 10ºC, 80-85% RH, the suberized layer of T-20 tubers increased to 24.0 µm, whereas there was no measurable increase in suberization in T-10 tubers. Higher curing temperatures resulted in significantly higher weight loss; cumulative weight loss at the end of storage was 2.8% and 3.6% for T-10 and T-20 tubers, respectively.  ‘Red LaSoda’ followed a similar trend as ‘Fabula’; T-20 tubers had a significantly thicker suberized layer (26.8 µm) than T-10 tubers (13.6 µm) at 14 d. Average weight loss in both storage conditions was 1.5% at 14 d; the more mature native periderm of ‘Red LaSoda’ tubers possibly minimized weight loss under the high curing temperatures. Tuber dry matter content was not affected by storage condition or duration, averaging 13.3% and 14.9% in ‘Fabula’ and ‘Red LaSoda’, respectively. These results indicate that a minimum of 5 d at 10ºC, 80-85% RH was sufficient to promote adequate wound-healing, while minimizing fresh weight loss, in these early season cultivars.