Short, Wild Carrot Is Long on Nematode Resistance

By Linda McGraw
August 10, 1998

Here's a sweet story about a short, wild carrot from Brazil that isn't sweet enough or orange enough to meet U.S. fresh market production standards. But it has one thing that our carrots don't have: a gene conferring 100 percent resistance to one of the major species of root knot nematodes.

Each year, root knot nematodes cause significant crop losses. About 60 percent of the nearly 100,000 acres of carrots grown in California are treated with soil fumigants to control these soil-borne pests at a cost of about $260 per acre.

To tackle this problem, an ARS plant geneticist in Madison, Wis., crossed nematode- resistant germplasm from Brazil with U.S. commercial varieties. Last year, Philipp Simon and a University of California nematologist planted seed from the first cross of the nematode-resistant carrots in one-acre plots at the University of California's Kearney Agricultural Center near Fresno, Calif.

Researchers planted both resistant and non-resistant carrots side by side in a field inundated with nematodes. When they measured the damage, the scientists found that nematodes had infected all non-resistant carrot roots.

The nematode-resistant carrots will be a welcome relief to growers. That's because the soil fumigants used to combat the nematodes may be banned during the next two to four years. Without these nematicides, commercial growers could lose up to 70 percent of their crop.

California produces 70 percent of U.S. fresh market carrots, with the remainder grown mostly in Florida, Michigan, Texas, Washington and Wisconsin.

More than 90 percent of the varieties used to produce the $400 million annual fresh market carrot crop are based at least in part on germplasm developed by ARS scientists.

Scientific contact: Philipp W. Simon, Vegetable Crops Research Unit, Agricultural Research Service, USDA, University of Wisconsin, Madison, WI (608) 262-1248 or 264-5406. E-mail: psimon@facstaff.wisc.edu.