P-595 - Citrus Yellow Vein Clearing Virus in California: Origin and Transmission

Abstract Text: Citrus yellow vein clearing virus (CYVCV), known to cause yield and growth reductions in citrus, is an emerging concern for California, United States. This research aimed to elucidate the global spread and local transmission dynamics of CYVCV in California. Spatiotemporal phylogenetic analysis, based on genome sequencing, traced the virus origin to approximately 1990 in South Asia and/or the Middle East, corroborating the initial report from Pakistan in 1988. Notably, California CYVCV isolates demonstrated diverse origins: Tulare isolates were associated with South Asian (India, Pakistan) and Middle Eastern (Türkiye) sources, while Hacienda Heights isolates were linked to East Asia (China, South Korea). Despite testing several reported insect vectors (Myzus persicae, Dialeurodes citri, Aphis gossypii, A. spiraecola) on various hosts, including citrus and herbaceous plants (common bean and cowpea), no vector transmission was observed for CYVCV CA isolates. A recent survey of Tulare citrus trees revealed c. 26% CYVCV-positive trees co-infected with non-insect-vectored citrus viroids (Citrus exocortis viroid and Hop stunt viroid), suggesting a dominant role for infected budwood in local dissemination. These results provide a distinct understanding of CYVCV transmission in California, contrasting with findings from other regions, and offer crucial insights for targeted control measures.