|SOWOKINOS, JOSEPH - University Of Minnesota|
|THILL, CHRISTIAN - University Of Minnesota|
Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2018
Publication Date: 4/2/2018
Citation: Sowokinos, J.R., Hayes, R.J., Thill, C. 2018. Coordinated regulation of cold induced sweetening in tetraploid potato families by isozymes of UDP-glucose pyrophosphorylase and vacuolar acid invertase. American Journal of Potato Research. 95:487-494.
Interpretive Summary: Cold storage of potatoes is useful for extending their shelf-life. To store potatoes destined to be processed into French fries or potato chips under cold temperatures, they must be able to resist the accumulation of the sugars glucose and fructose, a process referred to as sweetening. Potatoes that have sweetened, result in dark colored and bitter potato chips and French fries. Since cold storage is desirable but dark chips and fries are not, potato cultivars are often breed to be resistant to cold sweetening. This research characterized the role and interaction of the enzymes UDP-glucose pyrophosphorylase (UGPase) and acid invertase in potato breeding populations. These enzymes perform key biochemical steps in the flow of starch to glucose and fructose. The combination of low acid invertase activity and an isozyme of UGPase with low affinity for its substrate, resulted in the best resistance to cold sweetening. Plant breeders who select for this combination can expect to develop potato cultivars with good resistance to sweetening.
Technical Abstract: The goal of this study was to identify unique catalytic properties of hexogenic enzymes related to their role in regulating cold induced sweetening (CIS) in genetically diverse potato families. Inter- and intra-ploidy hybridizations of good (G) and poor (P) processing 24 or 48 chromosome potato clones were used to create 24 potato families. Potatoes were field grown and 460 progeny (=20 each family) were stored for five months in the cold (4 C). Tubers from each progeny plant were evaluated for cold induced sweetening resistance (CIS-R) and correlated with the percentage of A-II isozymes of UDP-glucose pyrophosphorylase (UGPase; EC 184.108.40.206); and acid invertase activity (AcInv; EC 220.127.116.11). Each progeny was given a CIS-R score of 1-10 (1-most resistance, 10 least resistance). The families were grouped into four classes based on (1) high of low AcInv activity (low being a SA of 0.30 or less) (2) high or low percentage of A-II isozymes (low being 50% or less), and (3) CIS-R score. In high AcInv families, CIS-R was low regardless of the percentage of A-II isozymes present. In low AcInv activity families, average chip color improved as the percentage of A-II isozymes increased. This increase in CIS-R in low AcInv families is likely due to the kinetic properties unique to the A-II forms of UGPase (principally UGP5) which limit the formation of sucrose via sucrose-6-phosphate synthase (SPS; EC 18.104.22.168). Less sucrose leads to a decrease in reducing sugar production via vacuolar AcInv resulting in lighter chip and fry colors. In selecting tetraploid parents, for the development of processing potato clones with improved CIS-R, it is recommended they have a basal AcInv SA of 0.30 or less and A-II isozymes of UGPase.