UCR wages $11+ million war against citrus greening disease
Three projects win funding to fight tree-killing bacteria
International Research Conference on HLB
Here in California
The International Research Conference on Huanglongbing VII (IRCHLB VII) is just around the corner! The California citrus industry is excited to welcome researchers, regulators, and citrus industry members from around the world to the Golden State. Do not miss these key dates:
A hotel room block with special conference rates has been set aside near the convention center and is filling up quickly. Book your room today at the Historic Mission Inn Hotel & Spa.
For the conference agenda, please click here. To register and access more conference details, CLICK HERE..
This Conference has occurred every two years (except for the covid period). Check out the Proceedings from previous conferences!
The proceedings of the “International Research Conference on Huanglongbing” are available from the 2008, 2011, 2013, 2015, 2017, and 2019 conferences. Please use the following hyperlinks to access the proceedings.
IRCHLB 2023
Three projects win funding to fight tree-killing bacteria
With three new grants totaling more than $11 million, UC Riverside is helping lead the fight against citrus greening or Huanglongbing, a disease threatening citrus industries in the U.S. and worldwide.
The disease is from bacteria transmitted to citrus trees by a tiny flying insect, the Asian citrus psyllid. Infected trees produce no fruit, or fruit that is bitter, small and worthless. Despite intensive research for the past 15 years, there is no known cure for it. It has reduced citrus production in Florida by more than 75%, and it has already been detected in Texas and California.
Because California supplies the country with 80% of its fresh citrus, and because 267,000 acres of Golden State lemons, oranges, grapefruits, and mandarins are at stake if operations are permanently lost, the USDA National Institute of Food and Agriculture is making an emergency investment in citrus disease research with three projects at UCR.
These projects focus on instilling tolerance to the disease with three different approaches: below ground, in the rootstocks, above ground in the shoots and branches, and systemically, with a peptide that would move throughout the tree.
The largest of the projects, at $6.8 million, is being led by Danelle Seymour, assistant professor of genetics in the Botany and Plant Sciences Department at UCR. Their focus is on breeding Huanglongbing or HLB-resistant rootstocks, and the project depends on collaboration with Kim Bowman, a citrus breeder at the USDA Agricultural Research Service in Ft. Pierce, Florida.
“In Florida, nearly every single tree is infected. It's terrible for growers, but wonderful for breeding,” Seymour said. “We can't do this research at large scale in California because the disease isn't as widespread here.”
The classic way to improve resistance or encourage new qualities in crops is through genetics, making crosses between one plant that has a favorable trait, and one that doesn't. “We hope the result is better than the parents,” Seymour said. “When you work in wheat or tomato, you can do these crosses and perform evaluations every year. In citrus, it takes 10 - 15 years to evaluate a new generation of trees.”
Because of the long lag time, the research-ready trees in Florida represent an opportunity for Seymour's team to begin examining new crosses now. The breeder, Kim Bowman, has evaluated over 10,000 trees and unique hybrids, from which a handful will be selected for release to growers.
In addition to evaluating these select few new hybrids for their HLB tolerance, the researchers will be watching the Florida-grown trees' responses to the different environmental conditions in California. “Can they perform well in response to different salinity levels in the soil, different humidity, as well as other pests and pathogens that we have here? We'll find out,” Seymour said.
Chandrika Ramadugu, a project scientist also in UCR's Department of Botany and Plant Sciences, is leading a project to develop HLB-resistant scion varieties that can be grafted to rootstocks. A scion is an above-ground portion of a plant, such as a bud or shoot, that can be used for grafting.
For trees, grafting can be equated to an organ transplant. The scion from one tree is attached to the trunk or rootstock of another with the hope of creating a new plant with combined attributes.
With its grant of $3.28 million, this project will analyze second-generation hybrids that are bred for ten years using Australian lime as a source of disease resistance.
Ramadugu will evaluate 24 novel hybrids in California, Florida, and Texas to assess resistance to HLB. Ideally, in addition to having enhanced disease tolerance, the new plants will also be able to produce good-tasting fruit.
There is little genetic diversity in cultivated citrus. When new pathogens arrive, the genetic uniformity can result in disease epidemics and dire consequences for the crop. In addition to the potential benefits of this project for the fight against HLB, the new hybrids may also help protect citrus from other pests and pathogens.
A third project, granted $1.36 million, will utilize a peptide found in Australian finger limes that is known to impart HLB resistance. Led by Hailing Jin, Microbiology & Plant Pathology professor, the project is developing ways to infuse trees with the peptide.
“The antimicrobial peptide in the finger limes are more efficient at killing bacteria as compared to antibiotics currently used in the field, and much more stable at high temperatures,” Jin said.
Because spray applications are expensive, Jin's project aims to spread the peptide throughout the trees' insides. In collaboration with University of Florida professor Svetlana Folimonova, Jin's team utilizes a natural citrus virus with almost no symptoms to deliver the peptide into the trees.
“You infect the tree with the virus, and it will spread in areas where the bacteria reside,” Jin said. “It would move systemically through the tree, and it would be very cost efficient for growers. No need to buy more insecticides.”
These grants were enabled by the 2018 Agricultural Improvement Act, which authorized the Emergency Citrus Disease Research and Development Trust Fund to fight HLB. With these and other projects, the USDA is bringing together the nation's top scientists to find scientifically sound solutions to the problem in a financially and ecologically sustainable way.
hlb tree pulled
HLB Quarantine Expansion |
Effective December 19, 2023, the Department is expanding the HLB quarantine boundary in the Santa Paula area of Ventura county in grid 437. A map of the proposed boundary can be found at https://www.cdfa.ca.gov/citrus/pests_diseases/hlb/regulation.html.
Also effective December 19, 2023, the Department is expanding ACP Bulk Citrus quarantine zone 6 in the Santa Paula area of Ventura county to reflect the newly expanded HLB quarantine area. A map of the new boundary can be found at https://www.cdfa.ca.gov/citrus/pests_diseases/acp/regulation.html
Regulated articles and conditions for intrastate movement under the quarantine can be found at Title 3 California Code of Regulations (CCR) sections 3435 & 3439. Pursuant to 3 CCR § 3435 & 3439, any interested party or local entity may appeal a quarantine area designation.
Process to Appeal the Proposed Expanded Boundaries The appeal must be submitted to the Department in writing and supported by clear and convincing evidence. The appeal must be filed no later than ten (10) working days from the date of this notification. During the pending of the appeal, the designated quarantine boundary under appeal shall remain in effect.
Mail Appeals to: CDFA - Citrus Division 1220 N Street Sacramento, CA 95814
Electronic Notification of Boundary Changes California Code of Regulation allows interested parties to be notified of quarantine area boundary changes, as well as the opportunity to submit quarantine boundary appeals. If interested in receiving notifications, please sign up for regulatory updates through the email notification ListServ at: https://www.cdfa.ca.gov/citrus/pests_diseases/hlb/signup-email-updates.html.
For questions regarding the regulations or map, please email Raymond Niem (Raymond.Niem@cdfa.ca.gov) or call 916.274.6300. |
Ventura Co. ACP/HLB Grower Liaisons
szwaal2@gmail.com (949) 636-7089
cressidasb@gmail.com (805) 284-3310
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hlb defprmed citrus
Transgenic Citrus Studies Progressing
Spray pesticides? Inject antibiotics? CUPS? Or?
The search for solutions to HLB has gone on for nearly two decades. Growers and researchers have learned ways to improve nutrition programs to keep trees alive and productive, but nowhere near at the level of the days before the disease.
One area of research that could yield a tree resistant to HLB is genetic engineering. There are no transgenic citrus trees produced commercially anywhere in the word, but trees are being developed by scientists.
Michael Rogers, director of the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Citrus Research and Education Center, discussed some of that research during the October All In For Citrus podcast episode.
While the industry has been cautious about genetically modified organisms (GMOs), the UF/IFAS citrus breeding team has been developing transgenic citrus varieties over the years. This is to keep the GMO option on the table and available if it can benefit the industry.
“Dozens of transgenic lines of citrus with robust tolerance to canker and/or HLB have been developed and tested in the greenhouse,” Rogers said. “Many of those lines are moving into field trials this year.”
In addition, researchers are testing a transgenic rootstock on a non-transgenic sweet orange variety. Rogers said the idea here is to see if the rootstock can pass on its HLB tolerance to the scion.
There are currently five lines of genetically modified Hamlin orange and one line of Duncan grapefruit that are moving through research and development. Field trials of these varieties were planted in 2019 and 2021. All have been infected by HLB in the field but are showing low HLB symptoms. Yield and quality data on these lines will be collected over the next two seasons. Requests for regulatory approvals are underway, which would allow the trees to be planted commercially.
Rogers expects the regulatory approval process will take more than two years, if successful. He emphasized this work has been ongoing for years now, so growers will have a GMO option if they need it and choose to plant it.
To learn more about this research, listen to the latest episode of All In For Citrus. The podcast is a partnership between UF/IFAS and AgNet Media.
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hlb infection
The recent find of an infected adult Asian citrus psyllid in Santa Paula prompted the search for the potentially infected tree by CA Department of Food and Agriculture personnel to spread out to look and test. Two trees were found and presumably they will be destroyed. This now prompts a much more intense survey of the surrounding 2/10ths of a mile of those trees. It also places a quarantine on the movement of fruit out of that area, extending out 5 miles. That means no fruit or plant parts should be taken out of the area, potentially spreading the insects and disease to other areas, unless those plant parts have been properly treated. You can read more about the actions taken in a quarantine when infected insects or plants are found HERE . And in this document you can read about the details in and around a quarantined area and how the fruit and plants should be treated HERE.
As is the case in the spread of many invasive pests, it is humans that can be the main mode of movement of the pest and disease.
ACP nymphs sam droege
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