Nematode-Resistant Bell Peppers Provide Alternative to Pesticide Use

Root-knot nematodes are common plant parasites that are found throughout the southern United States and across the world. These microscopic roundworms are found in the soil and on plant roots. They damage plants by feeding on root cells. The nematode’s rampant feeding on the roots can damage the plant’s root systems to the point where it can no longer absorb water and other necessary nutrients.

The roots of this susceptible pepper plant show extensive damage (thickened, lumpy portions) inflicted by a root-knot nematode. (Photo Credit: Scott Bauer/USDA)

The roots of this susceptible pepper plant show extensive damage (thickened, lumpy portions) inflicted by a root-knot nematode. (Photo Credit: Scott Bauer/USDA)

Root-knot nematodes are responsible for significant losses to field crops in sub-tropical regions. The most effective pesticide in the control of root-knot nematodes is methyl bromide (MeBr). This colorless and odorless gas is used as a soil fumigant. Although methyl bromide is very successful in killing microscopic parasites in the soil, it comes with a price. The use of methyl bromide has a negative impact on the environment–it has been implicated as one of the substances responsible for the depletion of the ozone layer. In addition, exposure to methyl bromide is a health risk to agricultural workers. In the United States, the use of methyl bromide has been phased out, in all but the most critical cases. However, it is still used in some third-world countries where pesticide alternatives cannot be easily accessed.

One way to overcome the need for noxious pesticides is to develop crops that are naturally pest-resistant. A team of scientists at the US Department of Agriculture-Agricultural Research Service, led by Dr. Judy Thies, are working to develop parasite-resistant vegetables. At the U.S. Vegetable Laboratory in Charleston, SC, researchers developed two varieties of parasite-resistant bell peppers.

The “Carolina Wonder” and “Charleston Belle” bell pepper varieties were made by backcrossing bell peppers to transfer the dominant N gene for root-knot nematode resistance from the “Mississippi Nemaheart” variety into the “Yolo Wonder” and “Keystone Resistant Giant” varieties. The “Carolina Wonder” and “Charleston Belle” varieties came from F3 populations derived after completing the sixth backcross.

In a study published in HortScience, a journal of the American Society for Horticultural Science, researchers tested how well the bell peppers fared when grown in areas with higher temperatures. To test their hypothesis, the scientists grew “Charleston Belle” and “Carolina Wonder” bell peppers in the higher-temperature soils of sub-tropic Florida. The researchers found that the nematode-resistant varieties did not break down when grown in hotter climates. These results indicate that the two new bell pepper varieties would be a suitable choice to grow in sub-tropic climates, reducing the need for pesticides such as methyl bromide. Currently, commercial seed companies are producing seeds for both pest-resistant varieties for use by both home and commercial growers.

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