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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Crop Improvement and Genetics Research » Research » Research Project #435865

Research Project: Development of "All Plant" Transgenic Citrus with Potential Broad Spectrum Disease Resistance Using Gene Gun

Location: Crop Improvement and Genetics Research

Project Number: 2030-21220-002-10-R
Project Type: Reimbursable Cooperative Agreement

Start Date: Oct 1, 2017
End Date: Sep 30, 2020

The purpose of this project is to produce marker-free transgenic citrus plants with broad spectrum disease resistance. These plants will be derived by biolistic (particle delivery) transformation and will contain only plant DNA derived sequences for genes, promoters, and terminators, and short non-coding recombinase recognition sites for recombinase-mediated cassette exchange (RMCE).

The introduction of genes by genetic transformation is a great tool to develop disease resistance varieties since we can insert one specific disease resistance gene in a plant without disturbing the genetic makeup of a good cultivar. The hindrances to genetic transformation are related to the time and cost of the deregulation process, since the transgenic plants produced are considered a regulated article by federal agencies if Agrobacterium tumefaciens was used for transformation, and if DNA sequences from pathogenic organisms are present in the plant. The latter include promoters, terminators and enhancers that are widely used in plant genetic transformation. In a regulated plant, all processes from planting the plants in the field to transit in and out of state are regulated by APHIS. If the plants produce any fruits, they have to be destroyed; even if we need to trim a plant, the plant parts need to be burned. Furthermore, the costs for the requirements needed to deregulate the plant are in the range of millions of dollars. In this project, genetically modified citrus plants will be produced that contain only plant DNA. Particle bombardment will be the method of transformation. Marker genes will be eliminated using recombinase technology established in our laboratory. The transgenic plants will not be produced by Agrobacterium tumefaciens transformation, and will contain only plant DNA, with the exception of recombinase recognition sites for site-specific recombinase manipulation. Neither these recombinase enzymes nor any of the construct DNAs are derived from plant pathogens nor are any of the sequences included in the list of organisms that are classified as regulated articles (see 7CFR340 document-APHIS ).