1a. Objectives (from AD-416)
Maintain a test site for evaluation of transgenic citrus scion and rootstock genotypes and expression vector strategies for resistance to Huanglongbing and the vector, Asian citrus psyllid.
1b. Approach (from AD-416)
A citrus production site will be maintained at the USDA/ARS Picos Rd. Farm for testing of transgenic citrus resistance to HLB and psyllid. Ongoing strategies to identify resistance to HLB and/or its psyllid vector include many transgenic approaches. All of these research projects ultimately require testing in the field where HLB and psyllid are endemic. The Picos Farm of the U.S. Horticultural Research Laboratory in Ft. Pierce, FL is ideal for this use. It is decided that the best use of this site is to test for HLB/psyllid resistance and control and therefore HLB infected trees are not removed and many citrus blocks are not receiving psyllid control sprays. This site will be available to UF, TAMU and ARS researchers. In addition to transgenic trees, some non-transgenic citrus with reasonable probability of resistance, will be tested.
3. Progress Report
This project is related to Objective 1: Create new genetic combinations of citrus, Objective 2: Screen germplasm for important traits and select superior individuals, and Objective 3: Evaluate selections for field performance and other traits. As proposed, a transgenic test site has been prepared at the United States Department of Agriculture Picos Farm in Ft. Pierce, where Huanglongbing and Asian citrus psyllid are widespread. The first trees have been in place for more than fourteen months. The University of Florida has provided 300 transgenic citrus plants expressing genes expected to provide huanglongbing/canker resistance, which have been planted in the test site along with an additional 89 tress including preinoculated trees of sweet orange on a complex tetraploid rootstock that appeared to confer huanglongbing resistance in an earlier test. The United States Horticultural Research Laboratory has a permit approved from the Animal and Plant Health Inspection Service to conduct field trials of their transgenic plants at this site, with several hundred planted rootstocks transformed with the antimicrobial peptide D4E1. More than 120 citranges, from a well-characterized mapping population, and other trifoliate hybrids (plus sweet orange standards) have been propagated for a replicated trial, will be planted in July 2011, and monitored for Liberibacter development and huanglongbing symptoms. Data from this trial should provide information on markers and perhaps genes associated with huanglongbing resistance, for use in transgenic and conventional breeding.