Merced County Cooperative Extension
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Posts Tagged: Georgios Vidalikis

You, too, can grow California’s oldest living orange variety

German Rafael Villalba-Salazar, nursery technician, harvesting budwood from mother citrus trees at the UC Citrus Clonal Protection Program facility. Photo by Stan Lim, UC Riverside

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.

Georgios Vidalakis, director of the Citrus Clonal Protection Program, posing with VI1000, the Bidwell's Bar orange tree. Photo by Stan Lim, UC Riverside

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.”

Program scientists graft citrus trees using budwood. Photo by Stan Lim, UC Riverside

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.

Posted on Thursday, June 9, 2022 at 9:47 AM
  • Author: Jules Bernstein, UC Riverside
Focus Area Tags: Agriculture, Food

Citrus industry, UC Riverside and UCCE team up to fight a citrus killer

Leaves on a Florida tree show symptoms of HLB disease. The new biosafety lab at UC Riverside will help scientists battle the disease. (Photo: Beth Grafton-Cardwell)
Researchers at the University of California, Riverside, will soon have a new resource to help them fight a disease devastating the citrus industry.

On June 6, citrus industry, university and government leaders gathered at UC Riverside Citrus Variety Collection to announce a joint effort to fight huanglongbing (HLB), also known as citrus greening disease. Huanglongbing is a bacterial plant disease fatal to citrus trees

The effort will result in construction of a biosafety-level 3 plant facility in Riverside, about two miles north of UC Riverside.

The biosafety-level 3 plant facility will allow researchers, including many from UC Riverside who are experts on citrus pests, diseases and breeding, to conduct work with plant pathogens that previously couldn't be done in Southern California. (There is only one other such facility in California – at UC Davis.)

The new biosafety-level 3 building will be built and owned by the California Citrus Research Foundation, which is funded by citrus growers.

At the June 6 gathering, Kim Wilcox, chancellor of the UC Riverside, spoke about the establishment in 1907 of the Citrus Experiment Station in Riverside. That research station eventually grew into UC Riverside. He noted that the research station received a boost after a 1913 freeze that devastated the citrus industry.

“Now, unfortunately, 100 years later, we have a different kind of natural threat, Wilcox said. “It's not weather in this case but an insect. And again the university, the federal government and private partners have come together and said ‘We can address this.'”

Georgios Vidalakis and Mark Hoddle are two UC Cooperative Extension specialists based at UC Riverside who will benefit from the facility.

Vidalakis is a UCCE specialist in plant pathology and director of the Citrus Clonal Protection Program at UC Riverside. The program provides a safe mechanism for the introduction into California of citrus varieties from around the world.

“Having access to live plants that carry the bacteria is very, very important to our program because it allows us to develop and validate diagnostic techniques much more quickly,” Vidalakis said.

Vidalkis has ongoing projects at the biosafety-level 3 plant facility in Davis as well as one in Maryland. Having his experimental material hundreds or thousands of miles away is a difficult, costly and inefficient way to conduct science, he said.

“This new facility in Riverside will help tremendously in the fight against HLB,” he said. “It is also a great investment for future threats to the California citrus industry.”

Hoddle is a UCCE specialist in entomology and director of Center for Invasive Species Research at UC Riverside. In recent years, Hoddle has released two species of wasps native to Pakistan that are natural enemies of the Asian citrus psyllid, the vector of a bacterium that causes HLB.

Hoddle called the biosafety facility a critical resource for righting HLB that will greatly assist UC Riverside researchers.

“This investment will likely allow more rapid and cost effect progress in developing mitigation strategies and novel technologies for managing HLB in California's iconic citrus crop,” Hoddle said.

Posted on Monday, June 13, 2016 at 9:47 AM

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