Determination of folate concentrations in diverse potato germplasm using a trienzyme extraction and microbiological assay

Authors: GOYER, AYMERIC - OREGON STATE UNIVERSITY; Navarre, Duroy - Roy

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2007
Publication Date: 5/2/2007
Citation: Goyer, A., Navarre, D.A. 2007. Determination of folate concentrations in diverse potato germplasm using a trienzyme extraction and microbiological assay. Journal of Agricultural and Food Chemistry. 55(9):3523-3528.

Interpretive Summary: Folate deficiency is a major cause of birth defects and linked to an increased risk of heart attacks, strokes and certain cancers. Besides transgenic approaches, one way to increase potato folate levels would be to identify germplasm with elevated amounts. Potato has tremendous genetic diversity in folate. Germplasms with high-folate are a useful source of genes to introgress into domesticated cultivars. Little is known about how much folate varies in different potato varieties as only a handful of cultivars have ever been analyzed. A similar situation exists in other plants where little is known about natural folate variation. We screened 67 diverse genotypes and found a 3-fold range between high and low folate containing genotypes. We also analyzed gene expression between high and low cultivars to see whether a molecular basis for the different concentrations could be identified. Our work suggests potatoes are likely an important source of dietary folate and suggests methods to increase folate concentrations in potatoes even further.

Technical Abstract: We determined total folate concentrations of potato tubers from 67 cultivars, advanced breeding lines, or wild species. Folates were extracted by a tri-enzyme treatment and analyzed by using a Lactobacillus rhamnosus microbiological assay. Folate concentrations varied from 521 ± 96 to 1373 ± 230 ng/g dry weight and were genotype and location dependent. The highest folate concentrations were mostly found in color-fleshed potatoes. Variations of folate concentrations among either color- or white-fleshed tubers were the same (1.97-fold difference). Skin contained ~40% higher folate concentrations than flesh. Storage of tubers for seven months generally led to an increase in folate content. Semi-quantitative RT-PCR analyses showed that higher folate contents were correlated with lower mRNA expression of folate catabolism genes.