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United States Department of Agriculture

Agricultural Research Service

Research Project: POTATO GENETICS, CYTOGENETICS, DISEASE RESISTANCE, AND PRE-BREEDING UTILIZING WILD AND CULTIVATED SPECIES

Location: Vegetable Crops Research Unit

Title: Rapid high throughput amylose determination in freeze dried potato tuber samples

Authors
item Fajardo, Diego -
item Jayanty, Sastry -
item JANSKY, SHELLEY

Submitted to: Journal of Visualized Experiments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 13, 2013
Publication Date: June 7, 2013
Citation: Fajardo, D., Jayanty, S., Jansky, S.H. 2013. Rapid high throughput amylose determination in freeze dried potato tuber samples. Journal of Visualized Experiments. 80:e50407. Available: http://www.jove.com/video/50407/.

Interpretive Summary: Potato starch is composed of approximately 75% amylopectin and 25% amylose. We are interested in breeding for higher amylose content, which would increase the fiber content of potato and decrease glycemic index. In order to make progress in a breeding program, we need a high throughput assay for amylose. This will allow us to screen large populations for individuals with high amylose in tuber starch. This paper describes a method using small samples in 96-well plates.

Technical Abstract: Approximately 80% of the fresh weight of a potato tuber is water; nearly all of the remaining dry matter is starch. Most of the starch (70%) is composed of amylopectin, while the remainder is amylose. The ratio between amylose and amylopectin is the most important property influencing the physical properties of starch. Amylose is a linear alpha 1-4 glucose chain, while amylopectin is a linear alpha 1-4 chain with alpha 1-6 branches. This protocol describes a colorimetric method that relies on the formation of a complex between iodine and chains of glucose molecules in starch. Iodine complexes with both amylose and long chains within amylopectin. After the addition of iodine to a starch sample, the maximum absorption of amylose and amylopectin occurs at 620 and 550 nm, respectively. The amylose/amylopectin ratio can be estimated from the ratio of the 620 and 550nm absorbance values and comparing them to a (standard curve)? in which specific known concentrations are plotted against absorption values. This high throughput, inexpensive method is reliable and reproducible, allowing the evaluation of large populations of potato clones.

Last Modified: 9/10/2014
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