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Plant Improvement – Page 3

2006 Henry J. Fisk (Genetic Engineering of Citrus)

Genetic Engineering of Citrus

The main focus of this project has been on the development of genetic transformation methods for citrus rootstock and scion cultivars important to the California industry. Establishment of this technology would represent a significant advancement towards efforts to better understand and improve these species using methods based in conventional breeding, biotechnology or a combination of the two.

2006 Henry J. Fisk (Development of Citrus Cultivars with Reduced Juvenility)

Development of Citrus Cultivars with Reduced Juvenility

The primary focus of this project has been to learn more about the flowering response in citrus in attempt to reduce juvenility. A key hypothesis that formed the basis of this work was that transgenic citrus species over-expressing a genetic regulator of flowering response from Arabidopsis thaliana or its functional equivalent from Washington navel orange would have reduced juvenility characteristics with respect to flowering.

2006 Tracy L. Kahn (Citrus Variety Evaluation for Trueness-to-Type and Commercial Potential)

Citrus Variety Evaluation for Trueness-to-Type and Commercial Potential

Changes in the domestic and international fresh citrus market, such as the increased market desire for seedless mandarins, and the rise in foreign exports into our market and other foreign markets intensifies global competition. To maintain and even increase California’s share of the domestic and global fresh citrus market, high quality varieties that best meet the market needs and are suited to California climates are essential for the California citrus industry.

2006 Mikeal L. Roose (Genetic Maps of Sweet Orange and Trifoliate Orange)

Genetic Maps of Sweet Orange and Trifoliate Orange

Genetic linkage maps are valuable for citrus breeding because they help breeders locate and select for genes that control valuable traits. They are also an essential component in geno-mics research. Linkage maps are based on the pattern of inheritance of short DNA sequences called markers. When two markers, or a marker and a gene that influences a trait, are located near each other on a chromosome, they are inherited together much more frequently than markers that are farther apart or located on different chromosomes. Therefore, a map that includes a high density of markers along all chromosomes allows breeders to locate trait genes that are inherited with the marker.

2006 Mikeal L. Roose (Citrus Rootstock Breeding and Evaluation)

Citrus Rootstock Breeding and Evaluation

Citrus rootstock breeding is a very long-term project aimed at providing the California citrus industry with a diversity of new rootstocks that improve productivity and profitability. New hybrid rootstocks and those imported from elsewhere are com-pared with standard rootstocks for yield, tree size, disease resistance, fruit quality, soil adaptation, compatibility with important scion varieties and other traits. Progress on the specific objectives of the 2005-2006 proposal is summarized below.