Making Spinach with Low Oxalate Levels

by Sharon Durham, Agricultural Research Service

Agricultural Research Service (ARS) scientists identified 8 spinach varieties that have low oxalate levels, which is sometimes linked to better health. Oxalic acid, or “oxalate,” is a naturally occurring plant chemical and in the human diet it’s been linked to kidney stone formation. It also can react with calcium, iron, and other minerals to inhibit mineral absorption.

Scientists with the ARS’s Crop Improvement and Protection Research Unit in Salinas, California, and the University of Arkansas conducted a study to find genetic components related to oxalate concentrations in spinach. By analyzing the genetic code of 310 spinach varieties, ARS geneticist Beiquan Mou and his university colleagues identified 6 DNA markers linked to genes that contribute to oxalate levels and may be useful for breeders in reducing oxalate concentrations.

The scientists analyzed oxalate concentrations in 300 USDA germplasm accessions and 10 commercial cultivars and found oxalate concentrations that ranged from 647.2 to 1,286.9 milligrams (mg) per 100 grams on fresh weight basis, according to Mou. They also found 8 accessions with less than 780 mg per 100 grams based on fresh weight that may be useful as sources of low oxalate concentration genes in breeding efforts.

Spinach contains higher concentrations of oxalate than most crops, but it is an economically important vegetable crop worldwide and it’s considered healthful because of its high concentration of a number of key nutrients. Foods such as beets, rhubarb, strawberries, nuts, chocolate, tea, wheat bran, and almost all dry beans also are known to increase oxalate in the urine and may contribute to kidney stone formation.

The results were published in November 2016, in the journal Euphytica.

Read more about Mou’s research in the January issue of AgResearch.

ARS is the U.S. Department of Agriculture‘s (USDA) in-house scientific research agency.