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ARS Home » Southeast Area » Fort Pierce, Florida » U.S. Horticultural Research Laboratory » Subtropical Insects and Horticulture Research » Research » Research Project #444117

Research Project: Genetic Improvement of Citrus for Superior Production, Marketability, and Tolerance to Huanglongbing

Location: Subtropical Insects and Horticulture Research

Project Number: 6034-21000-020-000-D
Project Type: In-House Appropriated

Start Date: Jul 3, 2023
End Date: Jul 2, 2028

Objective 1. Breed new citrus rootstock and scion cultivars with improved traits for successful commercial fruit production, including resistance or tolerance to diseases, including huanglongbing (HLB). 1.A. Select clones from among progeny groups and enter into replicated field trials. 1.B. Collect performance information from replicated field trials and identify outstanding clones for commercial release. Objective 2. Introduce useful traits into citrus populations by hybridization, transformation, and/or gene editing, and recombine traits to obtain combinations of traits representing superior new types. 2.A. Complete sexual crosses for new scion and rootstock types and establish into field for first evaluation. 2.B. Evaluation of transgenic citrus in field test site at USDA Picos farm. 2.C. Develop embryogenic cell lines for citrus CRISPR applications. Objective 3. Design novel breeding strategies such as genomic selection and create molecular genetic markers for fruit quality trait evaluation of citrus populations and efficient selection of elite materials. 3.A. Collect phenotypic data suitable for mapping and developing molecular genetic markers for traits associated with useful scion and rootstock characteristics 3.B. Map or associate genomic regions with useful traits and identify molecular markers Objective 4. Improve methodology to manage and evaluate new rootstock and scion germplasm for valued traits with a focus on tolerance/resistance to HLB and to employ these methods to develop and commercialize new cultivars. 4.A. Develop an in vitro HLB system. 4.B. Develop a UAV aerial imaging system for field trial data collection. 4.C. Develop a high throughput phenotyping method and data storage for commercial citrus scion and rootstock traits.

This project will focus on development of new citrus rootstock and scion cultivars with traits urgently needed for commercial production, especially improved marketability, and resistance to huanglongbing (HLB). These new rootstock and scion cultivars will enhance the competitiveness of the U.S. citrus industry by improving production efficiency, plant health, and market value of U.S. citrus crops. Breeding citrus for resistance to HLB is particularly difficult because of the long-life cycle of citrus, predominant apomixis among most cultivars, and lack of significant HLB resistance in the important cultivated citrus. The primary objectives of this project are to generate new citrus genotypes through conventional breeding, mutation, and genetic modification technologies; evaluate them as candidate cultivars for commercial use; and release new superior cultivars. In addition, improved methods will be developed for genetic modification of citrus, early selection of the most promising new hybrids using molecular markers, and more efficient field evaluation. Improved methods to pre-select and evaluate candidate hybrids will increase the success and pace of developing cultivars with the most important traits. Among global efforts to develop new citrus cultivars with HLB resistance, this program has the unique advantage of 1) numerous replicated field trials with hundreds of hybrids from which performance data is being collected for development of molecular markers and selection of superior new cultivars, 2) advanced breeding lines (produced by more than a century of introgression) which contain alleles for resistance to HLB and other critical traits from related species, and 3) excellent infrastructure including research field sites in two different production regions where the promising new scion and rootstock cultivars are evaluated. The planned research project will capitalize on these advantages to release superior new scion and rootstock cultivars, and to develop new germplasm, tools, and techniques that will accelerate the next generation of citrus breeding.