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Citrus variety collection Is a treasurehouse of diversity

The Issue

The citrus industry in California is worth $1.3 billion, making it one of the top 10 of California crops. Oranges, lemons, mandarins and grapefruit are each among the top 33% of California export crops. To sustain this level of productivity, citrus breeders, researchers and the citrus industry need access to collections of citrus genetic resources.

What Has ANR Done?

The UC Riverside Citrus Variety Collection (CVC), established in 1910, is one of the most extensive collections of citrus diversity in the world. This living collection includes two trees of each of the approximately 1,000 different types of citrus within 29 of the genera of the subfamily Aurantiodeae in the Rutaceae family.

Approximately 850 of the CVC varieties are in the subgenus Citrus, which contains the varieties we are familiar with. These include sweet oranges, sour oranges, mandarins or tangerines, lemons, limes, grapefruits, pummelos and citrons.

The CVC's diversity is apparent on sight, with fruits of unusual shapes, sizes and colors growing on trees of varying heights, forms and foliage. Fruit vary considerably in the chemical compounds of the rind and flesh, producing differences in nutriphytochemicals, taste, texture and aroma.

Underlying all of this tangible diversity is genetic diversity. Scientists can manipulate these genes, combining and transferring them to improve taste or disease and environmental tolerance, or to develop new food, beverage and horticultural crops.

The Payoff

The Citrus Variety Collection Is a Valuable Resource to the Global Citrus Community

The range of diversity within the collection provides a priceless resource for research. Currently, the collection serves a wide range of research projects on a diversity of topics, including citrus breeding; biological activities of citrus limonoids as anticancer agents; characterization of the different types for commercially important traits such as disease resistance/susceptibility; and the isolation, mapping and transferring of specific genes.

In addition, the USDA-ARS National Clonal Germplasm Repository for Citrus and Dates in Riverside uses the collection as its field site to fulfill its mission to acquire, preserve, distribute and evaluate genetic diversity. The CVC is the major source of observations documented on the National USDA GRIN database, available to the public (www.ars-grin.gov/npgs/searchgrin.html).

Beyond the research mission, the Citrus Variety Collection is used by a wide range of groups, such as research scientists from around the world; the citrus beverage industries; students; and the public.

Clientele Testimonial

"We've used the Citrus Variety Collection as a testbed for our business growing and selling unusual citrus varieties. We basically sell flavor, and the opportunity to taste unusual varieties of citrus, and the accumulated knowledge that resides in the heads of the program's staff, have proven invaluable to us as we continually search for varieties with excellent flavor and other characteristics that allow us to differentiate our fruit in the marketplace."

- Jim Churchill, Ojai grower of pixie tangerines and other nonmainstream varieties of citrus.


Supporting Unit: Botany & Plant Sciences

Tracy L. Kahn, Ph.D.
Curator UCR Citrus Variety Collection
Department of Botany and Plant Sciences
University of California, Riverside
Riverside, CA 92521-0124
Phone: 951-827-7360
Email: tracy.kahn@ucr.edu