UF researchers uncover how the pathogen evolves and spreads, with insights that may aid resistance breeding
Tomatoes are a $1.9 billion crop in the United States, planted on 330,000 acres across 18 states. But bacterial diseases—especially bacterial spot—pose a persistent threat to yields and farm profitability.
Bacterial spot has plagued tomato production for more than a century. Caused by several types of Xanthomonas bacteria, or xanthomonads, the disease is notoriously difficult to manage. One particular strain, Xanthomonas euvesicatoria pathovar perforans, was first detected in Florida over 30 years ago and has since spread across the eastern U.S.
With support from the USDA National Institute of Food and Agriculture, a global team of scientists led by University of Florida plant pathologists has uncovered why this pathogen spreads so efficiently. Their research found significant genetic diversity within the bacteria that cause bacterial spot, explaining how the disease can evolve quickly and travel across borders.
“This is a problem because when new genetic variation arrives in Florida, it may cause new problems, like more severe disease symptoms on tomato or spread to other crops like peppers,” said Erica Goss, a UF/IFAS plant pathology professor and one of the corresponding authors of the study, in a UF news release.
Over the course of a 12-year study, the team collected samples from tomato plants in 13 countries on six continents. They found the bacteria’s genetic makeup varied widely depending on location. The pathogen also survives in infected tomato seeds, which are traded and shipped globally—allowing it to move easily between regions.
“We already have a disease that is very hard to control in hot and humid weather around the world. It is a global problem that needs a solution,” Goss said. “What this study shows is that the pathogen is diversifying – there are lots of different types of the pathogen out there, and it’s evolving quickly to respond to control measures, which means there will not be a simple solution. But having this genetic information is critical to the development of disease-resistant tomato varieties, which would help farmers avert bacterial spot.”
Gary Vallad, a plant pathology professor at the UF/IFAS Gulf Coast Research and Education Center and a study co-author, said the findings offer valuable insight for breeders.
“Past efforts to breed for resistance to bacterial spot were compromised by the introduction of new strains, even before the resistance was commercially deployed,” Vallad said. “Knowledge of pathogen diversity allows us to refine our breeding efforts to target conserved genetic features within the global pathogen population. This should allow us to deploy resistance that is effective and durable. It also improves our ability to identify novel pathogen strains that could jeopardize commercial production and to monitor pathogen movement throughout the global production system.”
Tomatoes may be a staple in backyards and grocery stores, but their production hinges on staying one step ahead of fast-changing pathogens.
