MANIPULATING THE PRODUCTION EFFICIENCY OF POTATO WITH PLANT GROWTH RETARDANTS AND CHARACTERIZATION OF DEVELOPMENTAL AND POSTHARVEST PHYSIOLOGICAL PHENOTYPES OF ENGINEERED CULTIVARS
Ellis, Graham D
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Management techniques that reduce agronomic inputs, control tuber size, and prolong the postharvest quality of potato and its products will enhance the economics and sustainability of production. The research had three objectives: investigate low O2 storage for maintaining quality of fresh-cut (FC) potato, determine whether plant growth retardants can alter crop source/sink relationships to enhance production efficiency, and characterize the developmental and postharvest phenotypes of Innate®-engineered cultivars. For objective one, we demonstrated that respiratory and cold-sweetening responses of FC and whole tubers are similar. The lower O2 limit for aerobic metabolism in FC potato was ~2 kPa at 4oC, and lactate and EtOH accumulation were significant at ~1-1.5 kPa. Cold-sweetening and enzymatic browning of invertase-silenced (Innate®) and non-silenced FC tubers were reduced by hypoxia and abolished by anoxia. The results from this study inform development of modified atmosphere packaging for FC potato products. For the second objective, we demonstrated that the GA biosynthesis inhibitor, paclobutrazol (PBZ), could reduce foliar growth and increase tuber set in ‘Bondi’, which inherently produces excessive canopy growth, low tuber-set, and over-sized tubers. The PBZ-induced changes in allometric relationships increased harvest index without decreasing tuber yield and depended on concentration and application timing. Application timing can be managed to control tuber size while preserving the increased source/sink production efficiency. The third study demonstrated that developmental phenotypes and yields of the Innate®-engineered cultivars, Acclimate and Hibernate are equivalent to their respective parental cultivars, Ranger Russet and Atlantic. However, foliar growth and tuber-bulking rate of Glaciate was lower than Russet Burbank, resulting in lower yield. Changes in tuber respiration rates during sequential periods of cold-sweetening, reconditioning, and subsequent cold storage was comparable for the Innate® versus conventional cultivars, except for Glaciate where tuber respiration was elevated. Cold storage induced sucrose and reducing sugar buildup in Innate® and conventional tubers, respectively. Consequently, Innate® tubers maintained excellent fry and chip process quality regardless of storage temperature. Reconditioning permanently lowered the sucrose content of Innate® tubers. Heat stress exacerbated cold-induced sugar accumulation equally for all cultivars. The phenotyping trials provide information that will help optimize management practices.