Bullseye! Scientists Center in on Tomato Plants With Resistance to Target Spot
May 4, 2023 
Symptoms showing target spot of tomato.
Photo by Gary Vallad
Although target spot of tomato has been around for 50 years, it has become increasingly problematic during the last few years. With the pressure on, University of Florida researchers might have just found the key to developing tomatoes that can resist the deadly disease.
“No current tomato varieties resist the disease, and the only way to control it is through fungicides,” says Edgar Sierra, who just completed his doctoral dissertation on target spot resistance for the UF/IFAS College of Agricultural and Life Sciences. “However, target spot is increasingly resistant to several common fungicides, which drives us to develop resistant varieties.”
Target spot of tomato is caused by a fungus (Corynespora cassiicola) that infects hundreds of types of plants, including other crops like cucumbers, cotton, soybean, and others.
Working with faculty advisors at the UF/IFAS Gulf Coast Research and Education Center in Balm, Sierra used grow rooms to screen tomato seedlings for disease and discover sources of resistance. Then he tested mature plants in the field to understand how useful this resistance may be.
Results from field trials demonstrated that plants with target-spot resistance held up against the disease, even without fungicide sprays.
“We wanted to prove that the resistance identified in seedlings would translate to the mature plants in the field, and that was successful,” Sierra says. “This is very exciting, especially given that it’s difficult to find plants that resist pathogens such as target spot. This is also a very challenging disease because it is very easy to confuse it with other common diseases like bacterial spot or early blight.”
Fellow researchers and advisors at UF/IFAS think these findings could lead to development of the very first commercial varieties with target spot resistance.
“Together with an integrated disease-management plan, tomato hybrids with this novel resistance will help curb this increasingly relevant problem for tomato growers,” Sierra concludes.
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