- Author: Jeanette Warnert
The city of Riverside pitched a white tent over the "Parent Navel" orange tree at the intersection of Arlington and Magnolia avenues last week to protect it from the threat of huanglongbing disease, reported Ryan Hagen the Riverside Press Enterprise.
“The Parent Navel is an iconic symbol of Riverside, as it represents the impact the citrus industry had on our economy,” Mayor Rusty Bailey said in a press release issued by the City of Riverside. “Riversiders hold this symbol of our citrus heritage very dear, so it is encouraging to see our parks personnel taking a proactive approach.”
The tree was one of two planted by Eliza Tibbets in 1873, when she received the seedless orange cultivars from Florida by mail. Tibbets cared for the trees and sold budwood to nurseries, which led to extensive plantings of nursery trees cloned from hers.
Huanglongbing disease made its appearance in Riverside last year in residential trees. Officials are working to prevent its spread by controlling Asian citrus psyllid, the insect that can move the disease from tree to tree. Meanwhile researchers are searching for a cure.
The Parent Navel's high value led UC Riverside researchers and city officials to construct the large white barrier.
"It's not beautiful," said Georgios Vidalakis, UC Cooperative Extension specialist and director of the citrus clonal protection program at UC Riverside. "It's obstructing the tree from public view, and we apologize for that. But the risk from not doing that is catastrophic."
- Author: Ben Faber
The Citrus Research and Development Foundation (CRDF), a $124 million state citrus-industry initiative, has invested nearly 90 percent of its funds in HLB research. CRDF asked the Academies to review its research portfolio and determine if its efforts have followed recommendations outlined in the Academies' 2010 report, which originally called for the organization's creation. The committee found that CRDF was responsive to several recommendations from the previous report, and along with other funders, has advanced our knowledge about the disease. However, HLB remains a serious danger to Florida's citrus industry, having progressed from an acute to a chronic disease throughout the state.
The report notes that significant barriers to progress toward an HLB solution still exist, among them the inability to culture the bacteria in the laboratory, the lack of advanced diagnostics for early disease detection, and the absence of standardized research methodology that would improve the comparability of results across studies. Resolution of any one of these issues would constitute a significant step, according to the report.
The committee recommended continuing support for both basic and applied research for short- and long-term research efforts. In the long run, HLB solutions would likely utilize new technology, such as gene modification and gene editing, focusing on targets that mediate molecular interactions among plant, bacteria, and the vector, the committee said. As interest in using genetic modification in research grows, CRDF should also consider funding research to assess stakeholder acceptance of the technology and expand efforts to educate growers, processors, and consumers to facilitate the eventual deployment of genetically modified citrus lines.
In the meantime, growers in the state will need short-term solutions for the industry to remain viable. The report recommends finding the best suite of strategies to control the disease in different environmental and growing conditions, vector and pathogen pressures, tree varieties, and stages of tree health, which would help growers in Florida and other states where HLB also occurs.
The report also highlights the need to better understand the economic and sociological factors that impact decision-making and behaviors of growers, which influence the adoption of HLB management strategies. CRDF should create accessible databases to support sociological and economic modeling of citrus greening-related research outcomes and application projections.
The report recommends researchers communicate about the outcomes and evaluation of their efforts in a timely and systematic way. Additionally, current approaches to research prioritization and funding based within individual federal and state funding agencies have not led to development of a master plan for HLB research and subsequent management solutions. CRDF should work with other funding agencies to create an overarching advisory panel to develop a master plan for HLB research, communication, and management.
The study was sponsored by CRDF. The National Academies of Sciences, Engineering, and Medicine are private, nonprofit institutions that provide independent, objective analysis and advice to the nation to solve complex problems and inform public policy decisions related to science, technology, and medicine. The National Academies operate under an 1863 congressional charter to the National Academy of Sciences, signed by President Lincoln. For more information, visit http://national-academies.org. A roster follows.
To download full report: https://www.nap.edu/read/25026/chapter/1
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- Author: Ben Faber
RIVERSIDE, Calif. (http://www.
HLB, also known as citrus greening disease, has devastated groves in Asia, South America, and the southern U.S., costing the Florida citrus industry billions of dollars since 2005. Since 2012, the disease has been spreading in California's residential areas, prompting serious concerns about the state's commercial citrus groves.
HLB is associated with a species of bacteria called Candidatus Liberibacter asiaticus (CLas), which is transmitted by a tiny insect called the Asian citrus psyllid (ACP). Infected trees show leaf mottling, deformed and discolored fruits, and premature fruit drop. There is no cure for the disease and once a tree is infected it typically dies within three to five years.
An important step to developing HLB-resistant citrus varieties is to better understand how the bacterium infects trees and causes disease.
"Citrus trees, like all plants, have complex immune systems to prevent pathogenic infection, so the question is 'how does the CLas pathogen evade that immunity so it can cause disease?' said Wenbo Ma, a professor of plant pathology in UCR's College of Natural & Agricultural Sciences.
In a paper published Monday in Nature Communications, a team led by Ma reported a significant breakthrough in understanding the disease mechanism of HLB. They discovered that the bacterium secretes a protein--called Sec-delivered effector 1 (SDE1)--that helps infect plants. SDE1 works by attacking specific proteases--called papain-like cysteine proteases (PLCPs)--that could otherwise help the citrus trees resist infection.
"In the diseased trees we studied, the protein levels of some PLCPs were increased, presumably attempting to combat the bacterial infection," Ma said. "However, the bacterium fights back, by inhibiting the enzymatic activity of PLCPs through SDE1."
Ma said since scientists cannot grow CLas in the laboratory, the team used a surrogate system comprising the model plant Arabidopsis thaliana and the bacterial pathogen Pseudomonas syringae that was genetically engineered to produce SDE1. Using this system, they show that SDE1 promotes bacterial infection. This study is among the first to describe the molecular tactics employed by CLas to colonize citrus plants.
"This study represents an important step towards better understanding the HLB disease mechanism, which will help us develop novel approaches to control this unstoppable disease," Ma said.
The team is now investigating the molecular details of how SDE1 suppresses citrus PLCPs with the aim to use the CRISPR gene editing system to modify the proteases to become resistant to the inhibitory effects of SDE1.
###
The title of the paper is 'An effector from the Huanglongbing-associated pathogen targets citrus proteases.' In addition to Ma, authors from UC Riverside are Kelley Clark, Simon Schwizer, Eva Hawara, Deborah Pagliaccia, Liping Zeng, Jinxia Shi, Pengcheng Wang and Yinsheng Wang. Other authors include Jessica Yvette Franco, Thomas Liebrand and Gitta Coaker from UC Davis; Zhiqian Pang and Nian Wang from the University of Florida; Fatta B. Gurung and Veronica Ancona from Texas A&M University; and Renier van der Hoorn from the University of Oxford.
Funding was from the United States Department of Agriculture (USDA) National Institute of Food and Agriculture.
IMAGE: An orange tree that is infected with huanglongbing. Leaf symptoms begin on one or a few branches and slowly spread to the rest of the tree. view more
Credit: Georgios Vidalakis, UC Riverside
- Author: Ben Faber
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- Author: Ben Faber
A single breakthrough discovery for managing citrus greening in Florida in the future is unlikely, says a new report by the National Academies of Sciences, Engineering, and Medicine. The committee that wrote the report called for a systems approach to prioritize research on the disease and strategically distribute resources for research to effectively manage the disease, which is the most serious threat for citrus growers worldwide.
The disease Huanglongbing (HLB) or citrus greening — associated with bacteria that are spread by a sucking insect, the Asian citrus psyllid — was initially observed more than 100 years ago in Asia and was first detected in Florida in 2005. The infection results in blotchy mottling of leaves, stunting of shoots, gradual death of branches, and small, deformed fruits with bitter juice. Although infected trees do not die right away, they can remain in a steady state of decline for several years. Between 2010 and 2014, acreage of citrus trees in the state declined from roughly 750,000 to 476,000 acres, and production volume has declined by 58 percent since 2005. In Florida, citrus greening has caused a cumulative loss of $2.9 billion in grower revenues from 2007 to 2014, an average of $374 million a year.
The Citrus Research and Development Foundation (CRDF), a $124 million state citrus-industry initiative, has invested nearly 90 percent of its funds in HLB research. CRDF asked the Academies to review its research portfolio and determine if its efforts have followed recommendations outlined in the Academies' 2010 report, which originally called for the organization's creation. The committee found that CRDF was responsive to several recommendations from the previous report, and along with other funders, has advanced our knowledge about the disease. However, HLB remains a serious danger to Florida's citrus industry, having progressed from an acute to a chronic disease throughout the state.
The report notes that significant barriers to progress toward an HLB solution still exist, among them the inability to culture the bacteria in the laboratory, the lack of advanced diagnostics for early disease detection, and the absence of standardized research methodology that would improve the comparability of results across studies. Resolution of any one of these issues would constitute a significant step, according to the report.
The committee recommended continuing support for both basic and applied research for short- and long-term research efforts. In the long run, HLB solutions would likely utilize new technology, such as gene modification and gene editing, focusing on targets that mediate molecular interactions among plant, bacteria, and the vector, the committee said. As interest in using genetic modification in research grows, CRDF should also consider funding research to assess stakeholder acceptance of the technology and expand efforts to educate growers, processors, and consumers to facilitate the eventual deployment of genetically modified citrus lines.
In the meantime, growers in the state will need short-term solutions for the industry to remain viable. The report recommends finding the best suite of strategies to control the disease in different environmental and growing conditions, vector and pathogen pressures, tree varieties, and stages of tree health, which would help growers in Florida and other states where HLB also occurs.
The report also highlights the need to better understand the economic and sociological factors that impact decision-making and behaviors of growers, which influence the adoption of HLB management strategies. CRDF should create accessible databases to support sociological and economic modeling of citrus greening-related research outcomes and application projections.
The report recommends researchers communicate about the outcomes and evaluation of their efforts in a timely and systematic way. Additionally, current approaches to research prioritization and funding based within individual federal and state funding agencies have not led to development of a master plan for HLB research and subsequent management solutions. CRDF should work with other funding agencies to create an overarching advisory panel to develop a master plan for HLB research, communication, and management.
The study was sponsored by CRDF. The National Academies of Sciences, Engineering, and Medicine are private, nonprofit institutions that provide independent, objective analysis and advice to the nation to solve complex problems and inform public policy decisions related to science, technology, and medicine. The National Academies operate under an 1863 congressional charter to the National Academy of Sciences, signed by President Lincoln. For more information, visit http://national-academies.org.
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