US: Addressing resistance-breaking strain of tomato spotted wilt virus

The tomato industry is continuing to look for a solution to address the issues created by the resistance-breaking strain of tomato spotted wilt virus. The SW5 gene had been a significant breakthrough for the industry. Producers quickly adopted new cultivars with the gene that was shown to be resistant to the virus. It appears that the new strain of the virus has overcome the resistant qualities of the SW5 gene. Managing Director of the California Tomato Research Institute, Zach Bagley, said they need assistance from growers to identify potential solutions.

“We’re asking for grower help on the submission of information or samples from fields which have been planted to these resistant varieties with that SW5 gene, but which still have significant or what looks to be a significant impact of tomato spotted wilt virus,” said Bagley. “When I say significant, in this case, I’m meaning over one to two percent of the field looks to be impacted. In that case, there’s definitely something else going on, on top of that resistance dynamic.”

The new strain of the virus has been expanding its presence since its discovery in 2016. Its impact has been felt dramatically in Fresno County, with the new strain of the virus also moving into Merced, Kings, and Kern counties. “This is a major issue because to date there is no known source of genetic resistance to this new strain, or strains,” said Bagley.

“In other projects in this area, we are screening other materials including wild genetics,” Bagley noted. “We’re funding work to breed tomatoes that naturally repel insects using a compound called acylsugars and using CRISPR-Cas9 to identify the genetic markers for resistance so that we can eventually use traditional breeding practices to get that resistance back into our commercial varieties.”

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