Scientists with the Agricultural Research Service (ARS) may have found a potential remedy for the untreatable disease that has devastated the American citrus industry since it arrived in Florida in 1998. Huanglongbing (HLB), also known as citrus greening, is a disease that infects citrus trees in a way that renders the fruit useless and slowly kills the tree. Since 2005, HLB has spread throughout Florida, killing countless trees and devastating orchards. It is spread by the Asian citrus psyllid (ACP), a tiny sap-sucking insect that carries Candidatus liberibacter asiaticus (CLas), the bacterium that causes HLB. Psyllids transmit the disease by injecting a CLas-loaded salivary toxin into the tree as they feed. After that, there’s no hope for the tree.
Researchers at the ARS Crop Improvement and Genetics Research (CIGR) unit in Albany, CA, have discovered a way to augment the tree’s natural resistance to pathogens, including HLB. According to James Thomson, a geneticist at CIGR, by incorporating receptors that can recognize pathogens, they are able to activate a plant’s own innate immune responses.
The challenge in developing this approach was to identify the appropriate HLB-recognition genes, incorporate enough of them to be effective, and design a pathway to introduce them into trees.
One way to deliver the genes is to use agrobacteria. “Agrobacteria is a microbe that originated in soil, but has been turned into a plant engineering tool,” Thomson explained. “Essentially you clone the DNA of interest [in this case, from plants that have a natural resistance the pathogen of concern] and add it to the agrobacteria, then the agrobacteria adds that specific bit of DNA to the genome.”
Source: : agriculture.com