GAINESVILLE, Fla. – Tomatoes represent a $1.9 billion annual crop, nationwide. They’re planted on 330,000 acres across 18 states, but diseases such as bacterial spot can ravage the popular crop.
Bacterial diseases pose significant threats to food security by reducing crop yields and increasing production costs.
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Managing these diseases is challenging when pathogens are genetically diverse, evolve rapidly and are capable of traveling long distances.
Scientists and growers have battled bacterial spot worldwide for over 100 years. The disease is caused by several specialized forms of bacteria, referred to as xanthomonads.
However, a new xanthomonad, Xanthomonas euvesicatoria pathovar perforans, which causes the disease, was first discovered in Florida over 30 years ago and has since spread throughout the eastern United States.
Researchers are now discovering why it travels so well.
Thanks to funding from the USDA National Institute of Food and Agriculture, a global team of scientists led by plant pathologists from the University of Florida has found that the pathogen that causes bacterial spot has multiple genetic variations.
Bacterial spot travels when plants get infected with the pathogen and can survive in tomato seeds shipped anywhere in the world.
For the 12-year study, scientists collected the pathogen from tomato plants in 13 nations on six continents and found its genes vary greatly from country to country.
“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.
As bad as the news appears to be about how the disease travels, the study’s findings may help plant breeders.
“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 Gulf Coast Research and Education Center and a study co-author, said scientists can use the study’s findings to better monitor bacterial spot and develop tomatoes that can thwart the disease.
“Past efforts to breed for resistance to bacterial spot were compromised by the introduction of new strains, even before the resistance was commercially deployed. 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,” Vallad said. “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.”