California citrus tristeza virus survey

The principal application of this research is to obtain regulatory approval for the field release of GE-CTV in commercial citrus in the California as a mid-term control strategy to help mitigate HLB. Meanwhile, CTV regulation by the Interior CTV Quarantine in California continues with different implementation measures depending on the citrus pest control district (CDFA 2011). This quarantine is costly and difficult to maintain. The rootstocks now used by the citrus industry in California is tolerant or resistant to CTV and CTV strains currently found in commercial orchards do not cause significant economic impact. There are, however, occasional Quick Decline/Sour Orange tree death (O’Connell et al. 2010; Yokomi et al. 2020) but these are in 50-100 year-old trees that have survived CTV for all these years. Due to HLB, commercial citrus propagation in California is grown in protected enclosed structures using pathogen-free budwood, hence, the value of the CTV regulation is under increasing scrutiny and diminishing in priority. The proposed research can validate the economic concern of CTV if virulent strains of CTV are found. Moreover, the dominant wild type strains of CTV found in the survey will determine what strain(s) of GE-CTV can be deployed to avoid problems with cross-protection by same strain exclusion. If GE-CTV is approved, wild type CTV will likely have to be deregulated and the CCTEA is well-positioned to monitor spread of GE-CTV by naturally occurring aphid vectors.