Huanglongbing (Citrus Greening)

Huanglongbing (HLB) or citrus greening is a destructive disease of citrus trees worldwide and is associated with infection by the vector-borne bacterium Candidatus Liberibacter asiaticus (Ca. Liberibacter or CLas). HLB is widespread in Florida, as well as regions of Texas, Georgia, and Puerto Rico, resulting in significant financial implications.  Distinct regions of southern California are now under quarantine to limit dissemination. Recommended management practices for CLas infected regions include i) timely removal of the source of infection by uprooting infected trees, ii.) starting groves with disease-free seedlings, and iii) management of the vector population. Development of accurate, sensitive, and cost-effective means for detecting CLas infections in both citrus trees and Asian citrus psyllids, the insect vector that transmits CLas, is of paramount importance to the management of HLB.

Diagnostic Challenges

While technologically distinct methods have been described for the detection of CLas, they are complex and require trained personnel or expensive equipment. The standard of detection is a PCR based assay, which is often conducted at a central testing laboratory.  However, as amplification of DNA using isothermal amplification technology advances, such rapid assays are increasing adopted.

DxDiscovery solution. We aim to provide for the development of field-friendly assays that can be coupled with psyllid traps for a management strategy controlled by on-site farm stakeholders. Two antigen-capture immunoassays, a lateral flow immunoassay (LFI) and quantitative ELISA are being developed to meet the needs of the citrus grower. The LFI is an affordable, rapid platform that can be deployed in the field by citrus growers to assess the health of trees or trapped psyllids. Development of a complimentary ELISA will provide a quantitative means to carry-out large scale CLas testing in a lab or field station.

Market opportunity. When CLas is detected in citrus orchards, every effort is made to

eradicate the source. Simple and reliable on-site diagnostics are very important to carry out this

effort. Similarly, the current effort to identify sources of infection in backyards can be strengthened by the use of LFIs. In areas that HLB is widespread, such as in Florida, large-scale new plantings are being made. It is important to protect young trees from CLas infection to keep the industry economically viable, LFIs would be of great value since the grower can make instant management decisions.

R&D funding. Preliminary research into developing antibody-based tools for the detection of CLas was funded through a pilot grant funded by stakeholders at the California Citrus Nursery Board. Additional funding has been sought through the National Institute of Food and Agriculture.

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