Factors affecting tuber ascorbate content, physiological age, tuber set and size distribution in potato (Solanum tuberosum L.)

Potatoes (Solanum tuberosum L.) are one of the most important food crops globally and represent a multi-billion dollar market from production through retail. Areas of fundamental importance to consumers and producers include improving the nutritional quality of potatoes and enhancing their production value. The studies reported here focus in three disparate areas: (1) understanding how vitamin C accumulates during growth and development and is lost during storage in relation to expression of genes in the biosynthetic and recycling pathways; (2) testing the hypothesis that tuber respiration is the pacemaker of physiological aging in seed-potatoes; and (3) evaluating the efficacy of seed-tuber age and gibberellins (GA) to alter apical dominance, tuber set, and size distribution of five red/specialty cultivars to better meet the requirements of various markets.;AsA concentration increased rapidly in tubers during the early stages of tuberization and through bulking, reaching a maximum just prior to the attainment of physiological maturity, then fell during the maturation period as vines began to senesce. AsA was lost rapidly from tubers following harvest and the rate of loss was affected by genotype, tuber age, wounding, oxygen concentration, and sprouting; preventing this loss has the potential of greatly increasing the contribution of potatoes to vitamin C in our diet.;The importance of tuber basal metabolic rate in dictating the physiological age (PAGE) and productive potential of seed was explored in chapter two. Seed-tubers given high-temperature age-priming treatments at the beginning of storage maintained higher respiration rates throughout storage until planting. Lowering the respiration rate of age-primed seed during storage resulted in younger tubers. Respiration appears to be the pacemaker of PAGE and production and storage conditions that affect respiration may 'set the clock speed' that will ultimately determine the PAGE at planting.;Methods for manipulating apical dominance, tuber set and size distribution of specialty cultivars of potatoes were developed in chapter three. While aging treatments were ineffective, pre-plant applications of GA to cut seed substantially increased crop values, due to combined effects on apical dominance, tuber set, total yields and shifts in tuber size distribution toward smaller size tubers with higher value.