Genetic Analysis of the Emerging Citrus Yellow Vein Clearing Virus Reveals a Divergent Virus Population in American Isolates.

Citrus yellow vein clearing virus is a previously reported citrus virus from Asia with widespread distribution in China. In 2022, the California Department of Food and Agriculture conducted a multipest citrus survey targeting multiple citrus pathogens including citrus yellow vein clearing virus (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 noncitrus species, were collected and tested for CYVCV using conventional reverse transcription polymerase chain reaction, reverse transcription quantitative polymerase chain reaction, 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 17 complete viral genomes. Sequence analysis revealed two major phylogenetic groups. Known Asian isolates and five California isolates from this study made up the first group, whereas all other CYVCV isolates from California formed a second group, distinct from all worldwide isolates. Overall, the CYVCV population shows rapid expansion and high differentiation indicating a population bottleneck typical of a recent introduction into a new geographic area.

Differential detection of a surrogate biological threat agent (Bacillus globigii) with a portable surface plasmon resonance biosensor.

New methods and technology are needed to quickly and accurately detect potential biological warfare agents, such as Bacillus anthracis, causal agent of anthrax in humans and animals. Here, we report the detection of a simulant of B. anthracis (B. globigii) alone and in a mixture with a different species of Bacillus to test non-specific interference using a portable surface plasmon resonance (SPR) biosensor (SPIRIT 4.0, Seattle Sensor Systems). Both direct capture and antibody amplification were used to determine the limit of detection for spores of B. globigii, and to detect spores of B. globigii in a mixed sample containing another Bacillus spp. Spores of B. globigii were detected by anti-B. globigii (anti-Bg) coated sensors by direct capture at a concentration of 10(7)spores/mL, and with a secondary antibody amplification at a concentration of 10(5)spores/mL. Spores of B. globigii were differentially detected in a 1:1 mixture with B. pumilus spores from equal concentrations (10(7)spores/mL) with a secondary antibody amplification. To our knowledge, this is the first report of the differential detection of B. globigii with SPR in a mixed sample containing at least one additional Bacillus spp., highlighting the potential for SPR to detect any target bacterium in a mixed sample of closely related species. With the availability of portable instrumentation to accurately detect biological warfare agents such as B. anthracis, emergency responders can implement protocols in a timely fashion, limiting the amount of exposed individuals.