Breeding Spinach to Better Withstand the Pythium Pathogen

Breeding efforts at the U of A System Division of Agriculture to improve spinach tolerance to a pathogen called Pythium will help both indoor and outdoor growers of the popular leafy green.

The U.S. Department of Agriculture's National Institute of Food and Agriculture recently awarded vegetable breeder Ainong Shi and a team of researchers at the Arkansas Agricultural Experiment Station a $615,000, three-year grant to continue long-running efforts to identify spinach cultivars tolerant of multiple Pythium species. The experiment station is the research arm of the Division of Agriculture.

The grant is part of $10.2 million in funding for 18 projects supported by NIFA's Agriculture and Food Research Initiative program, which, among other things, supports public breeding efforts aimed at improving crop productivity, efficiency and performance.

In spinach production, Pythium can cause root rot that severely limits plant growth and may even lead to plant death, said Shi, a professor in the Department of Horticulture for the experiment station and the Dale Bumpers College of Agricultural, Food and Life Sciences at the U of A.

The fungus-like pathogen thrives in moist conditions, making it especially problematic for indoor growers using greenhouses, hydroponics or vertical-farming systems.

Inside and Out

Despite the advantages of controlled-environment agriculture for year-round production near population centers, most existing spinach cultivars were developed for open-field production and are poorly adapted to indoor conditions, Shi said.

"There are currently no highly resistant cultivars of spinach, although several lines with partial tolerance have been identified," Shi said. "This project focuses on improving Pythium tolerance rather than achieving complete resistance."

Co-principal investigators on the project include Jim Correll, Distinguished Professor of plant pathology in the Department of Entomology and Plant Pathology; Ryan Dickson, associate professor of greenhouse and controlled-environment agriculture in the Department of Horticulture; and Newton Kalengamaliro, director of research and development for Infinite Acres, a subsidiary of 80 Acres Farms, which has a facility in Springdale. 

The overarching goal of their project, "Development of Genomic Resources for Pythium Tolerance in Spinach," is to accelerate public spinach breeding by identifying genetic variation and developing genomic tools for the identification of tolerance to Pythium.

Genomic Selection

Shi uses a data-driven approach to estimate Pythium tolerance and evaluate multiple genomic prediction models. The practice speeds up the selection process for growing promising candidates.

To identify tolerant spinach lines, Shi and his team have been evaluating 480 diverse spinach genotypes, including 400 samples from the USDA Agricultural Research Service's Germplasm Resources Information Network, 50 commercial cultivars and hybrids, and 30 Arkansas breeding lines.

They hope to identify more than 30 Pythium-tolerant spinach lines and validate genomic prediction models to accelerate breeding for both soil-based and controlled-environment systems. 

Spinach Market 

Improving disease tolerance is increasingly important as spinach consumption continues to rise.

According to the latest data from the USDA Economic Research Service, in 2023, there were 3.1 pounds of spinach available per person, up from a previous record of 2 pounds per person in 2007. Its high nutritional value — including vitamins A, C, K and folate; essential minerals iron and calcium; antioxidants; and dietary fiber — has driven steadily increasing consumer demand for spinach. Much of the rise in fresh spinach consumption is the result of increased demand for packaged salad, the USDA report noted.

With nearly year-round production in the coastal valleys, California is the largest spinach-growing state, with about 65% of the nation's 56,200 acres of spinach. Other major spinach-growing states include Arizona and Texas, Shi said.

Although Arkansas is no longer a major spinach-growing state, the Arkansas River Valley was once a hotbed of spinach production and processing centered on Allen Canning Company in Alma. Correll said international seed companies have widely incorporated Arkansas spinach germplasm.

To learn more about ag and food research in Arkansas, visit aaes.uada.edu. Follow the Arkansas Agricultural Experiment Station on LinkedIn and sign up for our monthly newsletter, the Arkansas Agricultural Research Report. To learn more about the Division of Agriculture, visit uada.edu. To learn about extension programs in Arkansas, contact your local Cooperative Extension Service agent or visit uaex.uada.edu.

About the Division of Agriculture: The University of Arkansas Division of Agriculture's mission is to strengthen agriculture, communities, and families by connecting trusted research to the adoption of best practices. Through the Agricultural Experiment Station and the Cooperative Extension Service, the Division of Agriculture conducts research and extension work within the nation's historic land grant education system. The Division of Agriculture is one of 22 entities within the University of Arkansas System. It has offices in all 75 counties in Arkansas and faculty on three system campuses. Pursuant to 7 CFR § 15.3, the University of Arkansas Division of Agriculture offers all its Extension and Research programs and services (including employment) without regard to race, color, sex, national origin, religion, age, disability, marital or veteran status, genetic information, sexual preference, pregnancy or any other legally protected status, and is an equal opportunity institution.