Project Number: 6618-21000-013-42
Project Type: Reimbursable

Start Date: Aug 15, 2012
End Date: Aug 14, 2015

Objective:
To produce citrus scion genotypes which are resistant to huanglongbing and citrus canker through use of transgenic approaches.

Approach:
Both constitutive and phloem-specific promoters are being used. In the near term considerable effort will continue on antimicrobial peptides (AMP), using genes of synthetic or plant origin which are effective in-vitro against Xanthomonas citri pv. citri and bacteria related to Liberibacter. To enhance AMP activity we will test peptides that include a component with high affinity for the Liberibacter membrane, attached to a potent AMP, and expected to be effective at lower concentrations. Promoter sequences, message stabilizers, and transcription enhancers will all be explored to enhance expression of key transgenes. Canker resistant transgenics should be possible using solely citrus genes, fast-tracking deregulation for cis-genics by using the native promoter. Transgenic plants will be tested for resistance in the laboratory, greenhouse, and field. We also will continue to reach out broadly within the research community to identify other transgenes that merit inclusion. Expression of peach wild-type "dormancy associated MADS box" in Hamlin should induce deciduous behavior, reducing the CLas load annually by dropping leaves, altering phloem physiology during dormancy, and synchronizing flushing for better Asian citrus psyllid (ACP) control. A unique ACP-supporting Poncirus may reveal genes for ACP resistance.