2010 Annual Report
Late storage mottling (~190 days in storage) of Premier Russet appears to be a consequence of progressive increases in oxidative metabolism leading to accelerated aging during storage. The respiration rate of Premier Russet tubers is inherently higher than other cultivars (e.g. Russet Burbank). Respiration of mottled tissue was 1.8-fold greater than tissue from non-mottled tubers. In addition to higher concentrations of glucose, fructose, and sucrose, mottling resulted in lower dry matter, higher specific activities of starch phosphorylase and glu-6-phosphate dehydrogenase, higher protease activity, and loss of protein. Moreover, membrane integrity declined during mottling, likely due to increased peroxidation of membrane lipids. Superoxide dismutase activity and the ratio of oxidized to reduced glutathione were substantially higher in mottled tissue. Over maturation of tubers under dead vines at season end and high soil temperatures appear to increase the incidence and advance the onset of mottling in storage. These possibilities are currently being investigated.
Wound-healing ability declines with tuber age (storage period). We recently completed studies that show that the mechanism of age-induced loss in healing capacity is partly due to reduced ability of older tubers to synthesize ABA in response to wounding. ABA modulates the production of suberin polyphenolics through phenylalanine ammonia lyase. In contrast to younger tubers, wounding did not induce PAL expression in older tubers until five days after wounding. ABA treatment increased PAL expression and activity in tissue from both ages of tubers and corrected the 5-day transcriptional delay characteristic of older tubers. ABA treatment restored the healing ability of older tubers without restoring wound-induced superoxide-forming ability, suggesting a minimal role for wound-induced superoxide radicals in the oxidative coupling of phenolic monomers during suberization. However, the age-dependent loss of superoxide forming ability in response to wounding no doubt increases the susceptibility of older tubers to decay during wound-healing. Tubers also lose the ability to synthesize suberin polyaliphatic constituents in response to wounding with advancing age.
This project supports objective 1: Identify superior germplasm for potato disease- and pest-resistance, phytonutrients, minerals, and determine the extent of natural variation in diverse potato germplasm of select phytonutrients/metabolites.
This project was monitored through phone calls, email and meetings.