Genetic Improvement of Citrus for Enhanced Resistance to Biotic and Abiotic Stresses
Subtropical Insects and Horticulture Research
Project Number: 6618-21000-014-00
Start Date: May 01, 2013
End Date: Apr 30, 2018
1. Create new genetic combinations of citrus germplasm via conventional breeding, mutation, and transformation, to include rootstock and scion development and evaluation for essential traits of disease resistance and horticultural qualities.
1.A. Use sexual hybridization to create new germplasm from diverse parental types with useful horticultural characteristics.
1.B. Create new scions with useful traits through mutation.
1.C. Create new scions and rootstocks with potential resistance to huanglongbing and citrus bacterial canker by genetic transformation.
2. Develop and evaluate methods to improve citrus transformation, including the use of proliferating in vitro shoot cultures, as a novel source for genetic transformation and germplasm preservation.
2.A. Develop methods to produce proliferating in vitro shoot cultures of rootstock and scion types.
2.B. Determine the transformation efficiency of in vitro shoot cultures.
3. Develop and evaluate new methods to efficiently screen germplasm for important traits, improve the process of citrus variety development, and apply appropriate methods to select superior individuals.
3.A. Refine and evaluate methods to assess huanglongbing tolerance/resistance, and apply appropriate methods to select superior individuals.
3.B. Develop and apply methods to test selections for abiotic stress, including high pH.
4. Evaluate field performance and other traits for rootstock and scion slections and release new cultivars as appropriate.
New citrus selections will be created by sexual hybridization, mutation, and genetic transformation from existing cultivars and species. Sources of tolerance or resistance to huanglongbing will be emphasized in choice of parents for hybrids. Genes with potential to induce tolerance or resistance to huanglongbing will be emphasized in transformation, including anti-microbial peptides, chimeral anti-microbial peptides, citrus genes that respond to infection by the pathogen, but with regulation altered to increase resistance, and genes that target specific metabolic components of the pathogen. Methods will be developed to improve citrus transformation, including the use of proliferating in vitro shoot cultivars. Hybrids and other new types will be assessed for important traits, including the use of molecular markers, and greenhouse, laboratory, and field assays. Methods to assess huanglongbing tolerance or resistance and tolerance of high pH will be refined and applied to new hybrids and transgenics. Promising selections will be entered into long-term field trials at multiple locations, and data will be collected on tree health, size, fruit yield and quality. Selections that appear to have desirable combinations of traits will be released for commercial or dooryard use.