20 / SEEDWORLD.COM SEPTEMBER 2018 AT TRENDY SALAD bars, spinach vies with kale as king of the leafy greens. Long regarded as a nutrient-rich vegetable, spinach is replacing traditional salad lettuce with little nutritional value as a component of prepackaged fresh, leafy green salad mixes. It is now a year-round staple for health-conscious con- sumers. One reason for spinach’s popularity is its high nutrient content. According to the George Mateljan Foundation, spinach is the No. 1 food source of magnesium and iron and the No. 2 food source of several vitamins including B2, B6, E and K. Spinach is also a signifi- cant source of folic acid, calcium, potassium and vitamin A. Spinach Production Spinach falls into three types: savoy, semi-savoy and flat leafed with many cultivars of each. Savoy types are very productive and handle cold better than others. They have deeply crinkled leaves and a low growth habit that makes cleaning its leaves a chore. Semi-savoy spinach types have a more upright habit that makes mud splash less likely. Flat-leaf types have smooth, flat leaves that are easier to clean, which makes it the primary choice for processed spinach. “Baby spinach” is a term typically used to describe spinach that has been harvested during an early stage of plant growth, usually 15-35 days after planting. It is favored for its small leaves, tender texture and sweet taste in comparison with mature, fully- formed spinach leaves. Research shows that the concentration of nutrients in spinach is variable. Some studies conclude nutrients such as vitamin C, carotenoids and flavonoids are more concentrated in baby spinach leaves than in mature spinach. Other studies report the opposite. Nutrient variation appears to be the result of differences in the soil, season and climate in which the spinach is grown. The U.S. Department of Agriculture (USDA) reports U.S. growers in 2017 harvested over 53,000 acres of spinach. California growers harvested 60 percent of the crop while Arizona growers harvested 24 percent. China produces 85 to 90 percent of the total global spinach crop depending on the year. The U.S. is second largest producer with 2 to 3 percent of the world’s production. Plant Breeding Priorities Although U.S. spinach consumption has leveled in the past five years, plant breeders continue to aggressively seek to develop new hybrids. High on breeders’ priority list are resistance to three important diseases that affect spinach production: downy mildew, white rust and Fusarium wilt. Downy mildew is the most widespread and destructive spin- ach disease throughout the world, especially in California and Arizona. Though fungicide applications are available to control downy mildew in conventional production, adequate control measures are not available for organic production. New biofungicides continue to be evaluated to control downy mildew. More than 30 materials have been tested either in the field or under greenhouse conditions, but none of these materi- als effectively reduce downy mildew to commercially acceptable levels. While downy mildew is a soilborne disease, USDA researchers at Salinas, Calif., in 2015 found fertilized spores in 9 percent of the seed lots they tested indicating the disease is also seed borne. “The transport and spread of downy mildew on seed is a concern since the oospores can survive up to three years,” says Steve Klosterman, USDA research molecular biologist. “More work is necessary to determine if the viable oospores detected on spinach seed can infect spinach seedlings.” New genomic information may lead to improvements for a traditional health food. Joe Funk jfunk@issuesink.com SPINACH VYING TO BE KING OF THE LEAFY GREENS