The project has five objectives:(1) Remove the flowering-promoting CTV and the HLB bacterial pathogen in the transgenic plants(2) Graft CTV- and HLB-free buds onto rootstocks(3) Generate a large number of vigorous and healthy citrus trees(4) Plant the citrus trees in the site secured for testing transgenic citrus for HLB responses(5) Collect the field trial data In this quarter, we focused on the following greenhouse and laboratory work: (1) Took care of transgenic plants in the greenhouse. We now have two batches of transgenic plants. One batch have been prepared for the proposed field trial, but transplanting was delayed due to COVID-19. The other batch are newly produced, expressing a regulatory gene of systemic acquired resistance. These plants were regularly watered and fertilized. (2) Laboratory work was focused on cloning the extracellular domains of a group (10) of citrus homologs of an Arabidopsis disease resistance gene. This gene encodes a receptor-like kinase with the extracellular domain binding nicotinamide adenine dinucleotide. We found that overexpression of this receptor-like kinase increases resistance to bacterial pathogens and have thus generated transgenic citrus plants overexpressing the Arabidopsis receptor-like kinase gene. The citrus genome encodes more than ten homologs of this receptor-like kinase. To find out the functional homolog(s) of the receptor-like kinase gene, we cloned the extracelllar domains of the closest ten homologs in an E. coli expression vector. We are optimizing the protein expression conditions and will express and purify these fusion proteins from E. coli. The next step will be to test their nicotinamide adenine dinucleotide-binding activity. The protein(s) that binds nicotinamide adenine dinucleotide will be the citrus functional homolog and will be used to generate intragenic/cisgenic citrus plants.