1a. Objectives (from AD-416):
To identify the mechanisms of pathogenesis and natural defense in citrus to citrus greening disease or huanglongbing.
1b. Approach (from AD-416):
Complete greenhouse inoculation of citrus with huanglongbing (Candidatus Liberibacter asiaticus). Assess plant response and analyze changes in host plant small RNAs and mRNAs.
3. Progress Report:
This research related to all of the objectives of the inhouse project: 1. Create new genetic combinations of citrus germplasm via conventional breeding, mutation, and transformation. 2. Screen germplasm for important traits and select superior individuals. 3. Evaluate selections for field performance and other traits. This cooperative research is focused on a study of the mechanisms by which trees become infected with the diseases Candidatus Liberibacter asiaticus (Las) and citrus tristeza virus (CTV). The approach of the project is to use changes in host small RNAs and mRNAs as indicators of infection process and host plant reaction to the diseases. We have inoculated three genotypes, representing a range of host responses to the two diseases, and have collected tissue every ten weeks after infection. One rootstock clone, Cleopatra, becomes infected with both pathogens very quickly, while there is a long delay after inoculation before either pathogen can be detected in a second rootstock clone, US-942. Similarities in the responses of the host genotypes to both diseases suggest that there may be some similarities in the mechanisms and genetic basis of tolerance. Tissue is being prepared for small RNA analysis. Progress was monitored by conference calls, emails, meetings, and reports to the original funding agency.