Posts Tagged: UC Riverside Citrus Variety Collection
Sweet Mother Orange Tree released from quarantine
The 1000th tree okayed for growing by California's Citrus Clonal Protection Program happens to be the oldest living orange variety in the state.
The program, housed at UC Riverside, is the first of its kind in the world. It began in the 1950s, and its scientists spend up to three years testing and clearing citrus trees of disease so they can be released to commercial and private growers.
By law, every citrus tree newly propagated in California can be traced back to one mother tree created at UCR through the protection program. Program Director Georgios Vidalakis and his group begin their process by testing incoming trees for more than 30 citrus diseases, whether the diseases are known to have emerged in the state or not.
The treatment for any disease identified in that first round of testing is to make a new mini tree from a few cells of the original budwood — short, leafless twigs with buds meant for propagation. “We use special plant cells for this process that diseases cannot penetrate,” Vidalakis said.
After the mini tree grows large enough, program scientists go back and do a second round of testing for disease, making sure they picked the right cells for propagation and eliminating any prior trace of illness.
If it passes the arduous second set of tests, the new tree gets a variety index or VI number that accompanies it for the rest of its life, and it is released to the public.
Dubbed the Mother Orange Tree, Bidwell's Bar is a sweet Mediterranean orange brought to California from Mazatlán, Mexico, and planted in 1856. It was first planted near the Bidwell Bar Bridge near Oroville, then dug up and replanted twice.
Its survival skills are some of the reasons Tom Delfino, former California Citrus Nursery Society director, recommended the old orange tree for the protection program.
“Apparently this variety is very rugged,” Delfino said. “Not only has it survived a lot of cold Northern California winters, but the tree has been dug up and replanted twice — once to protect it from impending flood, and again to make way for the Oroville Dam.”
Much of the state's orange industry is based in areas with warm weather. Delfino, who lives in the San Francisco Bay Area, finds citrus an exciting challenge to grow. By suggesting Bidwell's Bar for approval, he was hoping the protection program would clear it so he could buy its budwood.
On the occasions he has visited the original tree, Delfino said the fruit in reaching distance was always gone. “I think it must be tasty because locals grab it for themselves,” he said. “Makes me even more eager to grow and eat my own. I'm extremely pleased the VI testing is completed so I can acquire it.”
Delfino also hopes that this variety will catch on with commercial growers.
“My thought is our citrus industry is concentrated in the southeastern San Joaquin Valley and is subject to a number of pests that like the warm climate there,” Delfino said. “Though this has seeds, which may be a deterrent, it can be grown in colder areas that discourage some of those insects.”
The tree arrived in California nearly two decades before the better-known Washington Navel orange grown by Eliza Tibbets in Riverside. The navel is named for a structure at the bottom end of the fruit, which resembles a belly button. This structure is actually a separate fruit inside the larger fruit. The Washington Navel is also seedless, contributing to its popularity.
“Bidwell's Bar is an example of what was grown in California before the Washington Navel came to dominate, and now that it has a VI number, others can grow it too,” said Tracy Kahn, curator of the Givaudan Citrus Variety Collection at UCR.
Kahn says it's important to preserve the genetic material from a tree with such significance to California. “Some people were worried it was going to die, but now we have an officially cleared source of this historic tree, and it is protected for future generations,” Kahn said./h3>
Among the topics is Asian citrus psyllid (ACP), which is off particular concern to citrus growers at the moment. The exotic pests can spread huanglongbing (HLB) disease, an incurable condition that has already seriously impacted the citrus industries in Florida and Texas. A few trees in urban Southern California backyards have been found infected with HLB and were pulled out and destroyed.
At the citrus field day, UC Agriculture and Natural Resources Cooperative Extension specialist Matt Daugherty will discuss the potential for nurseries to contribute to Asian citrus psyllid and huanglongbing spread. Regulations are in place in California that restrict movement of containerized citrus and require specific insecticide treatments. Daughterty is evaluating how well such steps reduce the risk of human-mediated Asian citrus psyllid spread. He is using a combination of monitoring in nurseries, field experiments on chemical control efficacy, and characterization of the effects of nursery practices on psyllid management.
Another speaker, UC ANR Cooperative Extension specialist Philippe Rolshausen, will explain how bacteria, fungi and viruses associated with plants, either on its surface or inside, can affect plant health and productivity. He will demonstrate how these organisms can be used for disease control using Pierce's disease of grapevines as an example and also drawing a comparison with huanglongbing in citrus.
The event, with a mix of presentations and field tours, is scheduled from 8 a.m. to 3 p.m. Advance registration, which is $25, is required. The deadline is Jan. 22. There will be no day-of-event registration available.
To register visit: https://form.jotform.com/53556635957975. For more information call (951) 827-5906.
The following is a tentative agenda:
- 8 a.m. – Introductions by Peggy Mauk, director of agricultural operations at UC Riverside and a subtropical horticulture extension specialist, and Tracy Kahn, curator of UC Riverside's Citrus Variety Collection.
- 8:10 a.m. – Welcomes from Kathryn Uhrich, dean of UC Riverside's College of Natural and Agricultural Sciences and Michael Anderson, a divisional dean for agriculture and natural resources
- 8:30 a.m. – Minimizing the potential for nurseries to contribute to Asian citrus psyllid spread in California – Matt Daugherty, UC ANR Cooperative Extension specialist, entomology.
- 9:15 a.m. – Microbiota-based approach to citrus tree health – Philippe Rolshausen, UC ANR Cooperative Extension specialist, subtropical horticulture.
- 9:45 a.m. – Low seeded citrus – variation in seed content and its causes – Mikeal Roose, professor, botany and plant sciences at UC Riverside. Roose specializes in plant breeding, particularly with citrus.
- 10:30 a.m. – Break
- 11 a.m. – Novel detection methods for Huanglongbing – Wenbo Ma, associate professor, plant pathology at UC Riverside .Her research is focused on developing methods that detect Huanglongbing by monitoring so-called “effectors” secreted from the bacterial pathogens causing the disease.
- 12 p.m. – Lunch (catered by Anchos Southwest Grill).
- 1 p.m. – Pesticide safety training – Vince Samons, UC Riverside agricultural operations.
- 1:45 p.m. – Walk-through of the Citrus Variety Collection, rootstock trial and phytophthora root rot trial.
To make a tax-deductible contribution to the Citrus Variety Collection Endowment fund or the Citrus Research Center & Agricultural Experiment Station support fund go to the following link and select College of Natural and Agricultural Sciences then select the specific fund: https://advancementservices.ucr.edu/GivingForm.aspx