Genetic analysis of the emerging citrus yellow vein clearing virus reveals a divergent virus population in American isolates

Citrus yellow vein clearing virus (CYVCV) is a previously reported citrus virus from Asia with widespread distribution in China. In 2022 the California Department of Food and Agriculture (CDFA) conducted a multi-pest citrus survey targeting multiple citrus pathogens including CYVCV. In March 2022, a lemon tree with symptoms of vein clearing, chlorosis and mottling in a private garden in the city of Tulare, California tested positive for CYVCV, which triggered an intensive survey in the surrounding areas. A total of 3,019 plant samples, including citrus and non-citrus species, were collected, and tested for CYVCV using conventional RT-PCR, RT-qPCR, and Sanger sequencing. Five hundred eighty-six citrus trees tested positive for CYVCV, including eight citrus species not previously recorded infected under field conditions. Comparative genomic studies were conducted using seventeen complete viral genomes. Sequence analysis revealed two major phylogenetic groups. Known Asian isolates and five California isolates from this study comprised the first group, whereas all other CYVCV isolates from California formed a second group, distinct from all worldwide isolates. Overall, CYVCV population shows rapid expansion and high differentiation indicating a population bottleneck typical of a recent introduction into a new geographic area. .