5 minute read
Bugs Without Borders: Plant Viruses in The Wildland-Urban Interface
By Susana Rinderle
Did you know that plants can get viruses too? Plant-infecting viruses are no fun. From farmers to houseplant owners, many of us have done battle with such pests. While scientists have mainly studied these viruses in the context of agriculture, the insects that transmit them aren't bound by the artificial boundaries of human gardens or farms. In fact, wild plants are often hosts to crop-associated, insect-borne viruses. Studying wild plants can, therefore, provide insight into how viruses evolve, how viruses and host plants affect each other, and how human development impacts native species that we strive to protect.
Dr. Tessa Shates, PhD., an entomologist trained at the University of California at Riverside (UCR), set out to gain such insight by studying three wild plants and their domesticated cousins. She wanted to know: (1) What viruses are present in these wild plants, and how prevalent are they? (2) What are the impacts of virus infection?
Tessa and her co-authors combined field, laboratory, and greenhouse methods to find these answers. First, they sampled and monitored leaf tissue from the Motte Rimrock Reserve (University of California Natural Reserve System) and the Shipley-Skinner Multispecies Reserve in 2017. They focused on buffalo gourd, coyote melon, and sacred thorn-apple (sacred datura). In 2019, she was awarded the Howie Wier Memorial Conservation Grant from Anza-Borrego Foundation, which allowed her to expand the research to include Anza-Borrego Desert State Park (ABDSP).
They selected these wild plants for their similarities to crops. Buffalo gourd and coyote melon are in the same genus (Cucurbita) as squash, zucchini and pumpkins. Sacred thorn-apple is in the nightshade family (Solanaceae), which includes tomatoes, potatoes, eggplant and peppers.
"The plants I studied are also culturally significant – buffalo gourd was a food source for indigenous communities through the southwest and a likely progenitor of cultivated squash. Sacred thorn-apple has medicinal and religious uses." - Dr. Tessa Shates
She therefore predicted that these wild plants would be susceptible to the viruses of their crop relatives. Following field sampling, Tessa used laboratory techniques to identify suspected viruses in the plants. She found that all three are often infected with at least one cropassociated virus, but usually more! One of those viruses – Cucurbit aphid-borne yellows virus (CABYV) – was highly prevalent in all three reserves. These findings show that viral infection affects traits likely relevant to multi-year survival. As the largest and least "disturbed” by human activity of the three study reserves, Tessa predicted that the plants in ABDSP would be the least likely to host crop viruses. However, that's not what she found.
Following field sampling, Tessa used laboratory techniques to identify suspected viruses in the plants. She found that all three are often infected with at least one cropassociated virus, but usually more! One of those viruses – Cucurbit aphid-borne yellows virus (CABYV) – was highly prevalent in all three reserves. These findings show that viral infection affects traits likely relevant to multi-year survival. As the largest and least "disturbed” by human activity of the three study reserves, Tessa predicted that the plants in ABDSP would be the least likely to host crop viruses. However, that's not what she found.
Because of these findings, Tessa and the team wanted to determine whether crop virus infection harmed the wild plants. She infected buffalo gourd and coyote melon seedlings in a UCR greenhouse with CABYV to determine how infection impacts plant health. She found that the roots and shoots of the infected squash weighed less than their healthy counterparts. Since these plants rely on large taproots to survive the winter and hot summers, they predict that virus infection might affect traits tied to multi-year survival.
"This work is relevant for Anza-Borrego Desert State Park because the three target plants grow within and around the Park. They provide resources for animals such as pollinating insects and other animals," says Tessa. "The plants I studied are also culturally significant – buffalo gourd was a food source for indigenous communities through the southwest and a likely progenitor of cultivated squash. Sacred thorn-apple has medicinal and religious uses."
Tessa's initial research was published in Frontiers in Microbiology in January 2019, and the paper on the expanded research in ABDSP is under peer review. Last June, she also presented her research at the "Anza-Borrego: In Focus" lecture series. In 2021, Tessa completed her PhD, focused on insecttransmitted plant viruses in the agricultural- and urban-natural interface. Currently, she is a Scientist in R&D Infectious Disease at Quest Diagnostics, working with a very different kind of bug!
If you would like to reach Tessa, visit her professional website, or contact her at Tshat003@ucr.edu .
