2012 Annual Report
1a.Objectives (from AD-416):
Four research objectives will be undertaken in this bridging project. Objective 1: Determine the roles, internal regulation, and the environmental responses of sucrose synthase, the predominant sucrolytic activity in sugarbeet root, in carbon partitioning to the root, sucrose utilization, sucrose yield, and sucrose retention during storage. Objective 2: Determine mechanisms of respiratory control and describe the endogenous processes and interactions with pathogens that affect sugarbeet root respiration rate during storage. Objective 3: Determine the inheritance and interrelationships among traits related to sucrose yield and extractability. Objective 4: Increase genetic diversity of the commercial sugarbeet crop by identifying and incorporating novel sources of pest resistance and crossing adapted sugarbeet lines with wild relatives of sugarbeet and selecting progeny for traits related to sucrose yield and sucrose extractability.
1b.Approach (from AD-416):
The goal of the proposed research is to increase the yield of extractable sucrose from the domestic sugarbeet crop through a fundamental understanding of the genetics and physiology of sugarbeet primary carbon metabolism. The research seeks to define and characterize the cognate genetic and physiological factors that influence sucrose accumulation, retention, and recovery during production, storage, and processing of the sugarbeet crop. In addition, research will introduce valuable genetic diversity into sugarbeet breeding germplasm through crossing adapted lines with wild relatives with novel traits.
Research to understand the role of the sucrose-degrading enzyme, sucrose synthase, in sugarbeet root sucrose accumulation and retention progressed. Although sucrose synthase has been suggested to function in phloem unloading and stress responses in other plants, research conducted under this project established that the enzyme is unlikely to serve these functions in sugarbeet root. In FY12, the intracellular location of sucrose synthase was determined. Results from this research provides evidence that sucrose synthase is likely to function in cell wall biosynthesis and suggests a role for sucrose synthase in root sucrose accumulation during development. Research to determine the metabolic factors that regulate sugarbeet root respiration also progressed in FY12. Previous research demonstrated that neither cellular energy status nor respiratory capacity limit respiration in stored sugarbeet roots, suggesting that storage respiration rate is restricted by the availability of one or more respiratory substrates. A metabolic profile of respiratory pathway substrates and intermediates in roots with different respiration rates identified an association between root respiration rate and cellular redox status. Ongoing research is testing the robustness of this relationship under different experimental parameters. Research to quantify the effect of production diseases on sugarbeet storage properties also continued. Previous research established that Aphanomyces root rot, rhizomania, and Fusarium yellows negatively affect sugarbeet root storage properties. In FY12, results from the second year of a four-year study indicated that Rhizoctonia root and crown rot also has a substantial negative impact on postharvest root storage properties. Breeding efforts have produced lines with low concentrations of some naturally occurring substances in sugarbeet that impede sucrose recovery during normal factory operations. Three germplasm lines with low levels of sodium, potassium, and amino-nitrogen, three of the substances that limit the proportion of sugar that can be extracted, were released in late 2011. Reduced levels of these compounds will increase payments to growers and factory efficiency. These lines will not only be useful in the production of adapted hybrids with enhanced processing quality but also will facilitate studies of the inheritance of sugarbeet processing quality. These lines bring the number of germplasm lines released over the life of this project to eleven.
Sugarbeet germplasm with improved processing properties released. Sodium, potassium, and amino-nitrogen are naturally occurring substances that accumulate in sugarbeet roots and impede sucrose recovery during normal processing. ARS researchers in Fargo, ND released three germplasm lines with substantially reduced levels of each of these substances. These lines are the result of numerous plant breeding cycles conducted in conjunction with chemical analysis of individual roots. Seed of the three lines is available for distribution to the public. These lines will provide germplasm for future improvement in sugarbeet processing quality, thereby increasing payments to growers and improving factory efficiency.
Fugate, K.K., Ferrareze, J.P., Bolton, M.D., Deckard, E.L., Campbell, L.G. 2012. Postharvest jasmonic acid treatment of sugarbeet roots reduces rot due to Botrytis cinerea, Penicillium claviforme, and Phoma betae. Postharvest Biology and Technology. 65:1-4.
Campbell, L.G., Fugate, K.K., Smith, L.J. 2012. Effect of pyraclostrobin on postharvest storage and quality of sugarbeet harvested before and after a frost. Journal of Sugar Beet Research. 49:1-25.