P-364 - Harnessing Dodder for Delivery of Infectious Clone to Recalcitrant Hosts

Abstract Text: Studying virus/vector/host interactions requires a reliable source of inoculum, which can often be a challenge. Infectious clones offer a well-characterized virus source, free from the complexity of quasi-species, and can be efficiently delivered to herbaceous hosts through agroinoculation. However, delivering these clones to woody hosts remains difficult due to their resistance to genetic transformation. For nearly a century, the ability of dodder (Cuscuta spp.), a holoparasitic plant, to transmit viruses between unrelated plant species has been recognized. To overcome the challenges of infecting woody hosts, we developed a novel dodder-based method to transfer infectious clones from an agroinoculated herbaceous host to a targeted host, such as Rubus spp. We also compared the efficiency of this method to traditional agroinoculation approaches. Using two infectious clones—one for the systemic blackberry chlorotic ringspot virus (BCRV) and one for the phloem-limited blackberry yellow vein-associated virus (BYVaV) (Sierra-Mejia et al., 2024a; b)—we found that our method significantly increased the transmission rates of both viruses to Rubus spp. Compared to direct agroinoculation, BCRV transmission rose from 9% to 73% (p=4.09e-06), whereas BYVaV transmission increased from 0% to 46% (p=0.005). The method described here efficiently delivers infectious clones to woody hosts, overcoming the limitations of direct agroinoculation, and enabling virus biology, virus-host interaction, and functional genomic studies otherwise limited to few crops.