Plant Improvement

2005 Abhaya Dandekar Seedlessness Strategies

Evaluating and Validating Seedlessness Strategies for Citrus

Seedy citrus fruit are a major quality issue and of significant concern to the citrus industry. Elimination of seed formation would be a valuable trait for many citrus cultivars, especially the mandarin varieties and seedy lemon varieties. In this project we will evaluate the role of ovule specific regulation of auxin to induce parthenocarpy in citrus.

2005 Peggy A. Mauk ( Mandarin Trial for the California Desert)

Mandarin Trial for the California Desert

Mandarin production has been a stable source of income for growers in the Coachella Valley for over three decades. Growers continue to have success with Fairchild Mandarin as well as with Minneola Tangelo. However, in order to stay competitive with domestic and global fresh citrus markets, there is a need for seedless mandarin varieties suitable for the California desert climate.

2005 Jose X. Chaparro ( Breeding a Red-Fleshed Mandarin )

Breeding a Red-Fleshed Mandarin (Candidate Gene Analysis)

The title of this project is “Breeding a Red Fleshed Mandarin,” subtitled “Candidate Gene Analysis.” The project has been a collaboration between Jose ChaparroJose Chaparro at the University of Florida, Andrew Breksa at the USDA-ARS facility in Albany, California, and Greg McCollum at the USDA-ARS-HRL at Ft. Pierce, Florida.

2005 Bryce W. Falk (Controlling CTV )

Controlling Citrus Tristeza Virus by Rootstock Delivery of a CTV RNA Silencing Signal

We completed the fourth and final year of our CRB-funded effort to develop Citrus tristeza virus (CTV) RNA silencing as an approach to confer systemic resistance against CTV.

2005 Mikeal L. Roose and Timothy J. Close ( Microarrays for Gene Expression)

Microarrays for Gene Expression and Mapping in Citrus

This project is best considered as a supplement to projects 5200-121 (EST Libraries and Bioinformatics) and 5200-125 (Genetic Maps of Sweet Orange and Trifoliate Orange) which use a new tool, microarrays, to study patterns of gene expression and map genes. Those projects are funded by CRB with matching funds from UC Discovery, but we are not permitted to spend those Discovery funds to purchase the microarrays necessary for the research. This CRB grant supplemented other UC funds and allowed us to purchase the chips needed to conduct the other projects.

2005 Mikeal L. Roose and Timothy J. Close (Genetic Maps)

Genetic Maps of Sweet Orange and Trifoliate Orange

This project is a collaboration involving the Roose and Close labs at UCR and the Fred Gmitter and Jose Chaparro labs at the University of Florida. The main goal is to develop genetic linkage maps of sweet orange and trifoliate orange. Genetic linkage maps are used to improve the efficiency of breeding and to identify genes that, if altered using biotechnology, would confer desired traits on the plant. The maps developed under this project will be the most detailed and accurate available for citrus. CRB funding enables us to obtain matching funds from the UC Discovery program (about $1.35 for each $1 of CRB funds).

2005 Timothy J. Close and Mikeal L. Roose ( EST Libraries)

EST Libraries and Bioinformatics for California Citrus

This project provides foundational information in the area of “Genomics”. The information is about the genes, proteins and metabolic pathways of citrus. This information facilitates other research and practical applications. Research applications include identification of genes that underlay pathogen resistance and development of transgenic strategies to investigate gene-trait relationships and develop new varieties. Practical applications include genetic markers for breeding and variety identification, and new methods to measure fruit quality.

2005 Abhaya M. Dandekar (Improving Peel Quality of California Citrus Fruit)

Improving Peel Quality of California Citrus Fruit

High quality peels are a critical component of high value fresh market citrus fruit. Peel quality is defined by the expression of specific gene sets during development that result in the development of the external finish of fresh fruit, a genetic phenotype that is a key factor for marketing of the product. Our study has two specific objectives: (1) To survey the pattern of genes expressed in peel tissues that determine quality of citrus fruit, and (2) To identify and validate genes associated with the development of fruit quality and peel related external finish disorders.

2005 Eduardo Blumwald (Physiological and Biochemical Determinants of Sugar and Acid)

Physiological and Biochemical Determinants of Sugar and Acid Content in Citrus Fruits and Citrus Fruit Proteomics.

Citrus fruit quality standards have been determined empirically, depending on species and on the particular growing regions. In general, the TSS (total soluble solids) to total acidity (TA) ratio determines whether citrus fruit can be marketed.

2005 Henry J. Fisk (Development of Citrus Cultivars with Reduced Juvenility)

Development of Citrus Cultivars with Reduced Juvenility

The overall objective of this project has been to develop technology that will allow for the creation of commercially important citrus species that have reduced juvenility. Since most citrus improvement programs involve the use of seedlings, plants with reduced juvenility will prove invaluable for expediting work that is based in conventional breeding, biotechnology, or a combination of the two due to a shorter time period required for screening, evaluations and/or subsequent crosses.