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Researchers from USDA's Agricultural Research Service (ARS) and their university partners are helping U.S. tomato growers fight a devastating crop disease. Researchers found that a tomato line developed 30 years ago is showing good resistance to the emerging tomato brown rugose fruit virus (ToBRFV), a virus that has the potential to cause billions of dollars in damage to the tomato industry in the United States and worldwide.

ToBRFV infects tomato, pepper, and similar crops by distorting leaves and discoloring fruit, resulting in yield loss. The virus is seed-borne and overcomes the resistance genes in current commercial cultivars. It can easily spread when healthy plants come in contact with contaminated equipment, hands, clothing, or infected plants or plant parts. The most effective way for farmers and growers to manage the virus is through prevention of contact with the virus, including cleaning, sanitizing, disinfecting, and maintaining clean growing areas.

"To minimize the impact of ToBRFV, it is crucial to identify new sources of genetic resistance that can be used to breed virus-resistant tomato cultivars," said Kai Ling, an ARS research plant pathologist at the U.S. Vegetable Laboratory in Charleston, SC. "While prevention is important, deploying cultivars with resistance genes is the critical strategy to combat tobamoviruses."

According to a published in Plant Biotechnology Journal, Ling and his research team found that a tomato line (tomato^NN) expressing the tobacco N gene that was developed in the 1990s shows resistance to ToBRFV. The tomato^NN line was created by ARS plant molecular geneticist Barbara Baker and her colleagues at the Plant Gene Expression Center in Albany, CA.

She and her team isolated the N gene from a wild tobacco relative that confers resistance to the tobacco mosaic virus (TMV) and developed the TMV-resistant tomato^NN line.

Ling and his colleagues discovered that the tomato^NN line is resistant to ToBRFV at 22°C (71.6°F), but the resistance decreases at higher temperatures, such as 30°C (86°F), which is characteristic of several resistance genes, including N-mediated TMV resistance.

"As we look at the possible virus-resistant tomato cultivars, it is important to understand the role that temperature plays in production," said Ling. "Temperature is a significant environmental cue that greatly influences host-pathogen interactions. Further study is needed to identify the role of temperature in the genetic resistance to tomato^NN."

The study's findings bring researchers one step closer to controlling ToBRFV.

"The results described in this paper highlight the significant potential of using the tomato^NN line to breed tomato cultivars resistant to ToBRFV and offers a new approach to managing this important disease for a beloved food staple," said Ling.