Submitted to: International Research Conference on Huanglongbing
Publication Type: Abstract Only
Publication Acceptance Date: 10/15/2014
Publication Date: 3/30/2015
Citation: Hao, G., Gupta, G., Duan, Y., Stover, E.W. 2015. Production of transgenic citrus resistant to citrus canker and Huanglongbing diseases. J Cit Pathol. 2(1):16. iocv_journalcitruspathology_30222.
Technical Abstract: Huanglongbing (HLB or citrus greening disease) caused by Candidatus Liberibacter asiaticus (Las) is a great threat to the U.S. citrus industry. There are no proven strategies to eliminate HLB disease and no cultivars identified with strong HLB resistance. Citrus canker is also an economically important disease associated with a bacterial pathogen (Xanthomonas citri). As part of the USDA citrus breeding program we are trying to develop citrus resistant to both HLB and citrus canker through expression of antimicrobial peptides (AMPs). In grape, enhanced Xylella fastidiosa resistance was reported from expression of a chimeral AMP-peptide (comprised of an AMP and a peptide with high bacterial membrane affinity) vs. the AMP alone. Our study is being conducted with the AMP D4E1, a plant thinion, and a chimeric AMP composed of D4E1 linked to thionin. We generated transgenic Carrizo and Hamlin with each of these constructs through Agrobacterium-mediated transformation. So far we have obtained many verified transformants of Carrizo and Hamlin with D4E1, thionin or chimeric AMP insertion. Gene expression was confirmed by reverse transcriptase PCR (RT-PCR) in some transgenic lines. Gene expression level was compared by RT-qPCR. Transgenic Carrizo lines containing these constructs were infiltrated with X. citri strain 3213. Several transgenic lines expressing the chimeric AMP or thinion alone showed marked canker resistance. Bacterial growth was inhibited in some transgenic plant lines expressing chimeric AMP and thinion but not those expressing D4E1 alone. These promising transgenic plants have been replicated and will be tested for HLB resistance.