Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/20/2016
Publication Date: 9/20/2016
Citation: Singh, R.K., Navarre, D.A., Brown, C.R. 2016. Relationship between sugars and phenylpropanoids in tubers from diverse genotypes. American Journal of Potato Research. 93:581-589.
Interpretive Summary: The lack of knowledge about how potato phenylpropanoid metabolism is regulated impedes the development of new cultivars that would have superior flavor and dietary value, along with improved disease and stress resistance. Scientists with the USDA-ARS in Prosser, Washington and Washington State University showed that the adding sucrose to plantlets increased the amounts of phenylpropanoids and that sucrose amounts in field grown potatoes correlated with phenylpropanoid amounts. Historically, the role of tuber sucrose is thought to be that of an energy and carbon source for the synthesis of various compounds. However, this data suggests sucrose also acts as a signal molecule that regulates tuber phenylpropanoid synthesis and therefore has an even more important role in potato physiology than previously realized. These findings create new opportunities to understand how sucrose influences tuber quality and to develop potatoes with higher amounts of phenylpropanoids that would enhance the nutritional value of potatoes and increase the resistance of potatoes to disease and other stresses that negatively affect yield and quality.
Technical Abstract: Previous studies suggested sucrose may play a regulatory role in potato phenylpropanoid metabolism via activation of MYB transcription factors, but the interaction between sucrose and phenylpropanoids has not been studied in field grown potatoes. Tuber sugars and phenylpropanoids were measured in over 100 different potato samples representing different genotypes, developmental stages and locations. Total phenolic content ranged from 1.6 to 17.0 mg/g dry wt and sucrose concentrations ranged from 4.7 to 132 mg/g dry wt. Sucrose was the most abundant sugar, followed by glucose and fructose. Overall, a modest positive correlation was seen between sucrose and phenolic concentrations. Typically, tubers with a higher concentration of sucrose contained higher phenolic levels. When the same cultivars were grown in multiple locations, the tubers with the lowest amount of phenolics also had the lowest amount of sucrose. The higher amounts of phenolics found in immature potatoes relative to mature potatoes also correlated with higher amounts of sucrose. Tubers infected with Zebra chip disease had higher amounts of phenylpropanoids, and also higher amounts of sucrose. These data support a regulatory role for sucrose in tuber phenylpropanoid metabolism and suggest that the absolute amount of tuber sucrose is important, but also changes in tuber sucrose homeostasis.