Researcher Manjul Dutt told a Citrus & Specialty Crop Expo audience in August why it can take up to 14 years to get a genetically modified citrus tree from discovery to commercial release. He also discussed the transgenic citrus progress at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS), where he is an assistant professor at the Citrus Research and Education Center (CREC).
HOW IT WORKS
Dutt noted that genetic transformation can modify the DNA of elite citrus varieties to enhance HLB tolerance. Genetic transformation is a process to modify the DNA of a plant (or any organism) to give it new qualities such as disease resistance, better yield, drought tolerance or pest resistance.
Scientists identify a useful gene —for example, a gene that helps citrus survive HLB, Dutt reported. They insert that gene into the DNA of citrus using one of several methods. Citrus then grows with that new ability (HLB tolerance).
TRANSFORMATION TIMELINES
Dutt provided timelines for the citrus genetic transformation and plant release process:
Year 1: Develop the DNA constructs and insert them into the plant’s cells. Develop the modified plant in tissue culture.
Years 2-3: Care for the trees in the greenhouse to support proper bud development for propagation. Conduct molecular analysis to identify superior trees.
Years 3-4: Propagate trees for replicated trials and evaluations (greenhouse and/or field).
Years 4-8: Evaluate trees in greenhouse and/or field for HLB tolerance.
Year 5 onward: Identify superior lines based on initial evaluations and establish larger multi-location field trials. Get germplasm certified through the Florida Department of Agriculture and Consumer Services Division of Plant Industry parent tree program. Initiate paperwork for eventual release.
Year 6 onward: The regulatory approval process.
Year 8 onward: Official cultivar registration. Planting material multiplication for large-scale nursery propagation. Market introduction, distribution and outreach to growers.
PROGRESS AND EXPECTATIONS
The UF/IFAS CREC citrus improvement program has evaluated hundreds of transgenic lines in the last 10 years. Dutt reported that two plant-based proteins, NPR1 and SABP2, have resulted in enhanced tree growth while reducing CLas levels in the phloem. CLas is the bacterium that causes HLB.
The CREC recently established a 20-acre genetically modified organism (GMO) evaluation field site to rapidly screen GMO scions and GMO rootstocks. Specific scion-rootstock combinations include:
- GMO sweet orange/grapefruit scion and non-GMO rootstock
- Non-GMO sweet orange/grapefruit scion and GMO rootstock
- GMO sweet orange/grapefruit scion and GMO rootstock
“We are generating field data that validates our preliminary observations, which will ultimately lead to GMO scions and rootstock release recommendations,” Dutt reported.
A population of trees with stacked genes that function in different ways is being produced.
Dutt noted that some wild citrus and some citrus relatives are resistant to HLB. Understanding their mechanism of resistance is providing researchers with genes to develop GMOs and genes for CRISPR.
See Dutt’s full Expo presentation here.
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