Several features of branched broomrape’s life cycle make them especially devastating for tomato producers. The weeds gain nutrients and water by attaching to tomato plants’ root cells, which prevents crop growth. Branched broomrapes’ flowers make thousands of seeds, which can remain dormant and viable in soil for more than twenty years, making planting future tomato crops risky. Despite mitigation efforts, the weed has been detected in several counties in California, a state that grows 90% of the country’s processing tomatoes.
When the broomrape attaches to tomato roots, many tomato genes respond to the parasitism with increased activity, which facilitates the attachment. A UC Davis research team led by Dr. Neelima Roy Sinha, professor of plant biology, is developing tomato varieties that do not turn these genes on in the presence of the parasite, making the root resistant to the infection, or compromising parasite growth. The project is identifying the genes that allow parasitic attachment in multiple processing tomato varieties, and assessing whether resistance in some tomatoes to the related weed Egyptian broomrape can provide additional genetic resources to combat branched broomrape. Finally, the researchers are generating branched broomrape-resistant tomato varieties using CRISPR-Cas9 gene editing technology to prevent gene expression.