Spinach: Van Deynze and Brummer seek answers to downy mildew, other challenges

Downy mildew makes those dry, tan-colored spots on spinach leaves -- a problem especially in organic cultivation. Growers have safety measures to ensure spinach is attractive, tasty and safe, but pathogens keep coming up with new ways to get around them, said Allen Van Deynze, associate director of the UC Davis Plant Breeding Center, directed by Charlie Brummer.

Researchers at the center, including associate breeder Allison Krill-Brown, are trying to develop new breeds of baby-leaf spinach that better resist downy mildew, take up less cadmium and use nitrogen more efficiently. The team is looking at spinach genes to find strains with those characteristics.

In the past year, they found several varieties with potential and have been testing them in the lab and out in the field for conventional and organic cultivation. They also are trying different testing methods, looking for ways to screen more lines of plants faster and using less space.

Another goal is to breed lines of spinach that can cycle more quickly from seed to plant to seed, Van Deynze said.

In 2021, the team tested more than 1,700 genetic lines of spinach. (Trials across several states were funded in part by a grant from the CDFA.) This summer, the team plans trials on farms in Davis, Salinas, El Centro and Tule Lake.

In addition, the team completed five tests on nitrogen use efficiency. They are looking for attractive color, leaf shape, flavor and productivity in soils with low nitrogen content.

Van Deynze presented the team's findings at the recent meeting of the California Leafy Greens Research Board, of the state Department of Food and Agriculture. The research is supported by the research board, seed industry grants, CDFA Specialty Crops Block grants and Specialty Crops-Multi-State grants.

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Learn more about the UC Davis Plant Breeding Center in this annual report.