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Drones
A panel of researchers discussed possible applications for UAS—unmanned aerial systems—at the recent American Peanut Research and Education Society (APRES) annual meeting in Albuquerque.

 

Ron Smith | Jul 19, 2017

The initial “gee whiz what a great idea” phase of unmanned aerial vehicle introduction has abated, somewhat, leaving the folks genuinely interested in using the technology for commercial endeavors now asking: “How will this amazing technology help me run my business?”

A panel of researchers discussed possible applications for UAS—unmanned aerial systems—at the recent American Peanut Research and Education Society (APRES) annual meeting in Albuquerque. Panelists Jamey Jacob, Oklahoma State University; Sarah Pelham, University of Georgia; Josh McGinty, Texas A&M AgriLife; and Maria Batola, Virginia Tech, agreed that unmanned aerial vehicles—drones—are capable of “taking pretty pictures,” but that extracting useful data from those images requires a bit of tedious work and ongoing study into how to collect and use data.

“Collecting data is a piece of cake,” Batola said. “We get beautiful pictures in 10 to 15 minutes, but it may take several hours to analyze the data from those images.”

And data, she said, is the reason to fly the drones. “Big data is a big deal. We want to develop phenotyping tools to aid plant breeders and to develop remote sensing tools to benefit agricultural producers.”

Batola says ag research has used ground unit remote sensing tools for years. “Now, we want to compare those with UAS.”

PRACTICAL APPLICATION

She said remote sensing studies at Virginia Tech have included efforts to estimate yields and to develop a nitrogen stability index. “We want to improve nitrogen management in wheat,” she said.

She’s looking at drought stress research in peanuts, evaluating various genotypes to observe wilting, yield and mature kernel potential, and crop values. “We want to find coefficients of correlation,” Batola said.

Pelham, a graduate student at the University of Georgia, is evaluating disease and phenotype relationships in peanuts “using unmanned aerial systems.” Tomato spotted wilt virus is a key disease target. She’s also looking at leaf spot and nematodes. “We want to use UAS to identify areas in the field with nematode infestations.”

She says different peanut genotypes show “different spectral signatures with different colors in the field.” Some varieties may be greener than others, for instance.

Drones also help evaluate stand count. “We can evaluate stands and determine a threshold for replant,” she said, “and we can determine where stands are thin and replant only those areas.”

Evaluating and predicting yield, she said, is another potential objective for UAS.

SYSTEMS EVOLVING

Jacob says making UAV technology an integral part of commerce has “a long way to go. The period of hype that comes with introduction of new technology does fade as some lose interest and some disillusionment sets in.” The task now, he said, is to find how to use UAS in a productive way.

The adoption will come, he added. “The current (younger) generation will be the last to get a driver’s license.” Driverless vehicles will become normal, he said. “Millennials, instead of having texting distract them from driving will think driving distracts them from texting.”

Agriculture, he added, will offer a big market for UAV use. “In Japan, UAVs have proven useful on small farms for spraying and other tasks.” Widespread use for more than imaging could be more problematic for large-scale farms. Potential uses include crop monitoring, chemical applications, and airborne imagery. But cost could be a factor. Manned aerial vehicles could, in some cases, be a better choice. Imagery would be takes from as high as 10,000 feet with a manned aircraft, he said. “UAVs have higher resolution, but do you need it? A lot depends on the cost and the crop value and what you need from the imagery.”

Jacob said UAVs will improve and find more uses. With normalized differentiated visual imagery (NVID) producers can identify areas of vegetation that are healthier than other areas. “We can get biomass estimations with added sensors and perhaps estimate crop yields. Plant diagnostic capabilities may improve to being capable of collecting data associated with a single plant.”

 He said automated weed databases will be configured to send data to automated ground vehicles that will target sprays.

REGULATORY ISSUES

Jacob says regulations continue to limit some uses. For instance, users currently have altitude limits and must keep the UAV in sight, which requires someone on the ground to monitor the vehicle. That could change in the future to allow a user to  monitor and control a unit from an office, collect data, process with a computer and take action from the information collected—without leaving the desk.

Challenges with that system include increased risk, insurance options and safety precautions.

He said technology is getting cheaper, but cost will be driven by the application and the size needed to perform certain tasks. A vehicle capable of spraying, for instance, would be heavier, and more expensive than a small rotor drone that mostly takes photos.

McGinty says in the future, UAS will be used to collect field data and use it for decisions or to evaluate research efforts. “We will collect and process data and determine what information will be useful and how best to use it. That’s the goal, but we’re not there yet.”

He’s using mostly rotor units for crop research evaluations, and fixed-wing for some pasture and rangeland studies. Fixed wing, he said, covers more area.

In research plots, he’s using drones to check plant growth, including plant height and canopy cover. Assessing plant health with NDVI is also a possibility. “We want to be able to use UAS data to predict yield,” he said. Drones are evaluating plant height and boll and bloom counts in cotton. “Boll counts have proven to be of less value than we anticipated,” he said. “But we are looking at different ways to use that data.”

He said looking at bloom counts may help identify stressed plants.

He’s also looking at sorghum. “We can collect images of sorghum panicles, but we have to count by hand. We want to automate that. But even having to do counts manually in the office is better than counting in the field in the heat and humidity of Corpus Christi.”

He said research on sorghum is in early stages. “We have only one year of data.

PROCESSING PROBLEMS

“Our biggest struggle so far is in sharing data,” McGinty said. “After collecting data, we may spend from eight to 12 hours processing it.” Going through a UAS Hub located at College Station streamlines the process.

The initial hype, Jacob says, has diminished. Regulations remain in place with the FAA still in control of drone flights, but rules are under review as more units are put in use and as technology improves control.

The key to making a drone a useful tool for agricultural research and for on-farm applications, the four researchers said, is to find ways to put the collected data to use in decision making. Data is the crucial factor, and the technology is not available yet to collect, process and use the information efficiently.

“Big data is essential for crop use,” Jacob said. “We can take pretty pictures, but we’re not to big data yet.”

 

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Science

Wheat in Oklahoma.
George Thomas/Flickr (CC BY-NC-ND 2.0)

Crop breeders sprout plan to boost public sector research

Universities need to get better at sharing patented seeds and other products of publicly-funded agricultural science if the United States wants to keep producing bountiful harvests, argues a new report from a group of leading academic researchers.

The 50 researchers also call on the federal government to provide better funding for crop breeding efforts at public universities, and for universities to develop new ways of steering revenues from popular crop varieties back into research.

The recommendations come amidst growing concern about the future of public-sector plant breeding programs. Researchers at private agricultural firms tend to focus on creating better varieties of widely-grown, high-value crops, such as wheat and corn. But the task of improving lower-value but still important crops—such as oats, potatoes, or forages for livestock—has been largely left to scientists at public universities and laboratories run by federal and state agencies. Public breeding has been withering, however, as it has become increasingly dependent on less reliable, short-term funding sources that make it difficult to sustain a year-round breeding program. And it has been hampered by intellectual property practices that can make it difficult to share genetic material and other resources.

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To identify solutions, researchers gathered in Raleigh, North Carolina, last year for an Intellectual Property Rights for Public Plant Breeding summit.

Plant genetic materials were once freely shared between institutions, the researchers note. But over the last few decades, university technology transfer offices have cracked down on how materials are exchanged and licensed—which has created confusion and slowed the creation of new varieties.

To speed progress, the group calls for the adoption of a “professional standard”—similar to a code of ethics—that facilitates immediate, easy sharing of cultivars and other breeding material. The group also wants farmers to be allowed to save seed from cultivars developed by the public sector. (Private firms often forbid such seed saving.)

Many problems boil down to unrealistic expectations within university technology transfer offices about the potential commercial value of new varieties, says Pat Hayes, a barley breeder at Oregon State University in Corvallis. On rare occasions, new breeds do reap impressive financial returns. The Honeycrisp apple generated around $14 million for the University of Minnesota before its patent expired, and new strawberry varieties developed at the University of California (UC), Davis, have generated $37 million over the past 5 years.

But even though most varieties don’t generate that kind of income, public universities often opt for overly restrictive intellectual property agreements in a bid to protect potential earnings from their use. “When it comes to tech transfer, it’s often a one-size-fits-all model, dominated by patents,” says wheat breeder P. Stephen Baenziger of the University of Nebraska in Lincoln. But there are other ways of protecting intellectual property that could ease sharing, he notes.

A conversation about better ways to distribute revenue generated by publicly-created crop varieties is also overdue, says Bill Tracy, a sweet corn breeder at the University of Wisconsin in Madison and one of the summit’s organizers. For example, he notes that the University of Florida returns royalties just to the inventor’s program when the revenue stream is relatively small, but spreads the wealth across the institution’s broader crop breeding programs when revenues are bigger. As a result, the report notes, Florida boasts more crop varieties released—and more graduate students supported—than similarly situated institutions.

Developing creative funding strategies may also be key to recruiting the next generation of public-sector crop breeders, researchers say. “Most of current faculty are long of tooth and gray of muzzle,” says Hayes, and “strategies able to create attractive academic positions … are needed.”

The timing may be ripe. “Tech transfer offices have had several years to realize that not everything is going to be the next UC Davis strawberry,” says Margaret Smith, a field corn breeder at Cornell University. “A patent for a crop variety,” she says, “isn’t the same as one for an engineering widget.”

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Science/AAAS

Examples of eight fruit fly brains with regions highlighted that are significantly correlated with (clockwise from top left) walking, stopping, increased jumping, increased female chasing, increased wing angle, increased wing grooming, increased wing extension, and backing up.

Kristin Branson

Artificial intelligence helps scientists map behavior in the fruit fly brain

Can you imagine watching 20,000 videos, 16 minutes apiece, of fruit flies walking, grooming, and chasing mates? Fortunately, you don’t have to, because scientists have designed a computer program that can do it faster. Aided by artificial intelligence, researchers have made 100 billion annotations of behavior from 400,000 flies to create a collection of maps linking fly mannerisms to their corresponding brain regions.

Experts say the work is a significant step toward understanding how both simple and complex behaviors can be tied to specific circuits in the brain. “The scale of the study is unprecedented,” says Thomas Serre, a computer vision expert and computational neuroscientist at Brown University. “This is going to be a huge and valuable tool for the community,” adds Bing Zhang, a fly neurobiologist at the University of Missouri in Columbia. “I am sure that follow-up studies will show this is a gold mine.”

At a mere 100,000 neurons—compared with our 86 billion—the small size of the fly brain makes it a good place to pick apart the inner workings of neurobiology. Yet scientists are still far from being able to understand a fly’s every move.

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To conduct the new research, computer scientist Kristin Branson of the Howard Hughes Medical Institute in Ashburn, Virginia, and colleagues acquired 2204 different genetically modified fruit fly strains (Drosophila melanogaster). Each enables the researchers to control different, but sometimes overlapping, subsets of the brain by simply raising the temperature to activate the neurons.

Then it was off to the Fly Bowl, a shallowly sloped, enclosed arena with a camera positioned directly overhead. The team placed groups of 10 male and 10 female flies inside at a time and captured 30,000 frames of video per 16-minute session. A computer program then tracked the coordinates and wing movements of each fly in the dish. The team did this about eight times for each of the strains, recording more than 20,000 videos. “That would be 225 straight days of flies walking around the dish if you watched them all,” Branson says.

Next, the team picked 14 easily recognizable behaviors to study, such as walking backward, touching, or attempting to mate with other flies. This required a researcher to manually label about 9000 frames of footage for each action, which was used to train a machine-learning computer program to recognize and label these behaviors on its own. Then the scientists derived 203 statistics describing the behaviors in the collected data, such as how often the flies walked and their average speed. Thanks to the computer vision, they detected differences between the strains too subtle for the human eye to accurately describe, such as when the flies increased their walking pace by a mere 5% or less.

“When we started this study we had no idea how often we would see behavioral differences,” between the different fly strains, Branson says. Yet it turns out that almost every strain—98% in all—had a significant difference in at least one of the behavior statistics measured. And there were plenty of oddballs: Some superjumpy flies hopped 100 times more often than normal; some males chased other flies 20 times more often than others; and some flies practically never stopped moving, whereas a few couch potatoes barely budged.

Then came the mapping. The scientists divided the fly brain into a novel set of 7065 tiny regions and linked them to the behaviors they had observed. The end product, called the Browsable Atlas of Behavior-Anatomy Maps, shows that some common behaviors, such as walking, are broadly correlated with neural circuits all over the brain, the team reports today in Cell. On the other hand, behaviors that are observed much less frequently, such as female flies chasing males, can be pinpointed to tiny regions of the brain, although this study didn’t prove that any of these regions were absolutely necessary for those behaviors. “We also learned that you can upload an unlimited number of videos on YouTube,” Branson says, noting that clips of all 20,000 videos are available online.

Branson hopes the resource will serve as a launching pad for other neurobiologists seeking to manipulate part of the brain or study a specific behavior. For instance, not much is known about female aggression in fruit flies, and the new maps gives leads for which brain regions might be driving these actions.

Because the genetically modified strains are specific to flies, Serre doesn’t think the results will be immediately applicable to other species, such as mice, but he still views this as a watershed moment for getting researchers excited about using computer vision in neuroscience. “I am usually more tempered in my public comments, but here I was very impressed,” he says.

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From PestNet/www.pestnet.org/Grahame Jackson

PhysOrg

https://phys.org/news/2017-05-four-billion-year-old-fossil-protein-resurrected-bacteria.html

 

old virus

This figure shows two possible outcomes from a viral attempt to infect the cell. On the left, the virus binds to the bacterium, injects its genetic info, and stops because it can’t recruit the needed proteins. On the right, the virus binds to the cell, injects the genetic info, recruits the proteins, and starts replicating, resulting in the cell bursting and releasing more viruses. Credit: Jose Sanchez-Ruiz

Read more at: https://phys.org/news/2017-05-four-billion-year-old-fossil-protein-resurrected-bacteria.html#jCp

 

In a proof-of-concept experiment, a 4-billion-year-old protein engineered into modern E. coli protected the bacteria from being hijacked by a bacteria-infecting virus. It was as if the E. coli had suddenly gone analogue, but the phage only knew how to hack digital. The ancient protein, an ancestral form of thioredoxin, was similar enough to its present-day analogues that it could function in E. coli but different enough that the bacteriophage couldn’t use the protein to its advantage. The work, which could be useful in plant bioengineering, appears May 9 in Cell 

“This is an arms race. Thioredoxin has been changing in evolution to avoid being hijacked by the virus, and the virus has been evolving to hijack the protein,” says senior author Jose Sanchez-Ruiz of the University of Granada in Spain. “So we go back, and we spoil all of the virus’ strategy.”

Sanchez-Ruiz’s lab specializes in reconstructing ancient gene sequences that code for proteins. Since proteins do not preserve for billions of years, the researchers make their best estimation of the ancient protein based on genetic data across many different taxa. Thioredoxin, a versatile work-horse protein that moves electrons around so that chemical reactions in the cell can occur, is a favorite in the lab because it has been around almost since the origin of life and it is present in all modern organisms. We can’t live without it, nor can E. coli.

Thioredoxin also happens to be one of the proteins that bacteriophage must recruit to survive and replicate. Without a hijack-able thioredoxin, the virus hits a dead end. In a series of experiments led by Asunción Delgado, then a post-doc at the University of Granada, the researchers tested seven reconstructions of primordial thioredoxins, ranging in age from 1.5 billion years old to 4 billion years, to see if they could function in modern E. coli.

The old-school thioredoxins passed the test with varying degrees of success. “That was a bit surprising,” says Delgado. “The modern organism is a completely different cellular environment. Ancestral thioredoxins had different molecular partners, different everything. The farther back we get from present, the less they work in a modern organism. But even when we get back to close to the origin of life, they still show some functionality.”

But the ancestral thioredoxins were just different enough that the modern phage couldn’t recognize or bind to them.

However, resurrecting ancient proteins may be useful as more than a scientific curiosity. Virologists tend to focus on the human-infecting ones, but the viruses that kill the most people are not human pathogens but rather the viruses that kill off crops, sparking famines and mass starvation. Delgado, Sanchez-Ruiz, and their colleagues speculate that ancient proteins could be edited into plants to confer protection against crop-killing viruses. However, this idea has yet to be tested in plants.

“If this is applied to plants, it wouldn’t be genes from ancient bacteria; it would be genes from the same plant. It would be the ancestral version of a gene from the same plant,” says Sanchez-Ruiz. “This is genetic alteration, of course, but it is a mild genetic alteration. This is not like having a gene from one species being transferred to a different species. Also, this would not be like Jurassic Park. It would just be a comparatively small change in a gene that the plant already has.”

Protein resurrection experiments could also shed light on how evolution works at the protein level. “What we can do is let the virus evolve to adapt to the ancestral protein, and then do the experiment in reverse,” says Sanchez-Ruiz. “Once it’s adapted to the ancestral protein, we can test how it reacts to the modern protein. We can see if it repeats the evolution. So it would be kind of a molecular version of this Stephen J. Gould ‘replaying the tape of life’ idea.”

The researchers’ next set of experiments will focus on the fundamentals of protein evolution, but they point out that understanding and resurrecting old proteins could be a key resource for biotech. Instead of introducing new elements, bioengineers may be able to re-use older ones from earlier in viruses and cells’ co-evolutionary history. “Some people think that evolution is just a theory or is just some kind of philosophic explanation,” says Sanchez-Ruiz. “Evolutionary studies have practical applications.”

Explore further: ‘Digging up’ 4-billion-year-old fossil protein structures to reveal how they evolved

More information: Cell Reports, Delgado et al.: “Using Resurrected Ancestral Proviral Proteins to Engineer Virus Resistance” http://www.cell.com/cell-reports/fulltext/S2211-1247(17)30531-4DOI: 10.1016/j.celrep.2017.04.037

Journal reference: Cell Reports

Provided by: Cell Press

Read more at: https://phys.org/news/2017-05-four-billion-year-old-fossil-protein-resurrected-bacteria.html#jCp

 

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ktic_logo

BY KSRE | April 13, 2017

Kansas State University, Australian Researchers Join Forces to Combat Insect Pest

Photo courtesy of KSRE

MANHATTAN, Kan. – Researchers at Kansas State University and the University of Queensland in Australia have joined forces to attack and control a microscopic pest that can be devastating to the fruit, vegetable and flower industries.

Ralf Dietzgen, an associate professor in agriculture and food innovation at the University of Queensland, is spending three months at K-State as a Fulbright Senior Scholar in a quest to gather data and develop control measures for the small insect known as thrips.

Dietzgen is working directly with plant pathology professors Dorith Rotenberg and Anna Whitfield, who are co-directors of the Center of Excellence for Vector-Borne Plant Virus Disease Control.

Not known to grow larger than 3 millimeters, thrips are voracious eaters, using their asymmetrical mouths to puncture the surface of food crops, flowers and leaves and suck up their contents.

Of equal concern to researchers is that thrips are vectors, or carriers, of more than 20 viruses that cause plant disease, especially the tospoviruses, which also multiply in thrips. Given the right conditions, such as those found in greenhouses, thrips can reproduce exponentially and form large swarms that can transmit viruses to healthy plants.

“They’re very challenging to control, for several reasons,” Whitfield said. “For one, the insect is hard to kill. It is resistant to many insecticides. You can’t just spray crops and hope to control the spread of thrips and tospovirus.

“But secondly, the viruses that thrips can spread are very diverse and can change quickly. I call tospoviruses the influenza of the plant virus world. The predominant virus threat may change because they can switch genome segments and can develop resistance to control measures based on genetic changes. So the viruses have a lot of diversity themselves.”

Whitfield said Dietzgen’s lab in Australia is one of a few in the world that studies viruses that replicate in insects and plants.

“The thrips are a significant pest and have an impact on food security and then on top of that they transmit viruses which cause disease symptoms on the produce, like ring spots, which make them unmarketable,” Dietzgen said.

He noted that when thrips feed on flower buds, the developing fruits often become misshapen. “So you have peppers that are crooked and unmarketable,” Dietzgen said.

“We are studying thrips and the viruses they transmit at the molecular level with the goal of developing applied control strategies,” Whitfield said. “We think that better understanding the molecular mechanisms of the interaction is essential for developing sustainable control strategies for thrips and tospoviruses.”

Dietzgen recently saw first-hand the devastation that thrips-transmitted viruses can cause. One Queensland grower who provides fresh tomatoes for a large supermarket chain lost most of his crop one year due to a tospovirus transmitted by thrips. The lost crop was valued at more than $500,000.

“By the time the grower saw the disease effects, the thrips had moved on and the virus had been left behind,” Dietzgen said.

“The virus that Ralf is studying isn’t in the U.S. just yet, but thrips insects are able to move around easily so that they could appear hidden in a shipment of produce,” Whitfield said. “Any shipment of vegetables or plants that is traveling around the world could have similar pathogens and pests in it. As a control measure, we are trying to develop broad spectrum, durable resistance using different technologies.”

While Dietzgen’s stay at Kansas State University is relatively short, the researchers hope their new partnership will help lead to long-term solutions for agriculture.

“Both of our labs have generated large sets of genomic data that we’re starting to compare during my stay,” Dietzgen said. “By doing that, we hope to come up with potential targets for pest and disease control for longer term crop protection. We are asking, ‘What are the functions of these potential molecular targets and can we interfere with them?’”

Rotenberg and graduate student Derek Schneweis have compiled large sets of data outlining the messenger RNA molecules in thrips. Whitfield said their work may give new insight into how to control thrips in horticultural crops, as well as how to protect those crops from tospoviruses and other plant disease.

The prestigious U.S. Fulbright program is the largest educational scholarship of its kind, and was created after World War II by U.S. Sen. J. William Fulbright. It operates between the U.S. and 155 countries.

More than 20 Fulbright Scholarships are awarded each year to Australian students, postdoctoral researchers, academics and professionals to pursue studies or conduct research in the United States.

In 2014, Kansas State University became the first U.S. educational partner of the Australian-American Fulbright Commission. Each year since, the university has hosted Fulbright Scholars from Australia to study and collaborate with Kansas State University researchers.

Kansas State also helped form the Oz to Oz program to encourage exchanges with faculty at Australian universities, often as seminar speakers.

© 2017 Nebraska Rural Radio Association. All rights reserved. Republishing, rebroadcasting, rewriting, redistributing prohibited. Copyright Information

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SE farm press

citrus-greening-university-florida-asd
This approach to controlling citrus greening, by blocking bacterial transmission by the psyllid, runs contrary to existing ‘kill the insect’ strategies.

Logan Hawkes | Mar 04, 2017

Since the introduction of Huánglóngbìng (HLB–yellow dragon disease–or better known as citrus greening disease) reared its ugly head on U.S. soil in a Florida citrus grove in 2005, the disease has been a major threat to commercial citrus production across the country.

Before arriving in North America, HLB had already carved a path of destruction across the Far East, Africa, the Indian subcontinent and the Arabian Peninsula, and was discovered in July 2004 in Brazil. In its wake it left citrus growers around the world astounded at the inevitable and long-lasting risks the disease poses to global citrus industry.

During the first couple of years after reaching Florida, the disease had destroyed a huge section of the state’s successful citrus industry, and by 2009, just five years after its introduction in the region, almost every county within Florida had confirmed HLB cases among both commercial and private citrus groves. From there the disease spread

to adjoining states, eventually reaching citrus growing areas in Texas and finally as far west as California.The fight against HLB and the tiny psyllids that carry the bacteria from tree to tree is about as old as the disease itself. Recognizing the disease had the ability to threaten the global citrus industry, researchers from around the world began working on possible solutions to combat the spread of this dangerous citrus killer.

In spite of early efforts however, the tell-tale signs of the disease kept spreading.

 The early symptoms of HLB include leaves with yellowing veins appear along with asymmetrical chlorosis referred to as “blotchy mottle.” These are the most diagnostic symptoms of the disease, especially on sweet orange. Growers, ever fearful the disease would reach their trees, have been on constant lookout for leaves that are slow to develop and often with a variety of chlorotic patterns that often resemble mineral deficiencies such as those of zinc, iron, and manganese.

Regardless of treatment efforts, once established in a grove, the end result of the disease is proving to be inevitable, the complete decay and destruction of all infected trees.

Detection of the disease is one of the first hurdles facing citrus growers in modern times. When it comes to fighting HLB, growers face a number of unique challenges. For one, HLB-infected citrus trees do not show symptoms during the first year of infection, so there is a long period of time when a grower cannot visually detect an infected tree. But that hasn’t stemmed research efforts.

The spreading pandemic of the disease served to rally the global citrus industry and the many researchers who support it. Soon new and innovative treatments were being tested. In addition to antibacterial management and control and management of the psyllids that carry the disease, tree removal became a standard procedure to help curtail the rapid spread of the bacterium.

Soon, beneficial parasitoids were introduced and widely used to help control psyllid populations. Heat treatments in nurseries and on field trees covered by plastic wrap offered some slowing of the disease process in early research efforts. Hundreds of millions of dollars were being spent worldwide searching for a cure to the disease. A zinc-based bactericidal spray seemed to offer some hope.

Before long, breeders were offering new citrus varieties that were proving resistant to the bacterium that causes HLB. Bio-engineers have been devising methods to make citrus trees less attractive to the psyllids that carry the disease. But in recent months a new idea has surfaced, and while no one is ringing the bell of victory, researchers on the project are quietly voicing new hope in the war against the disease.

HOW IT WORKS

According to researchers, the reproductive and feeding habits of the psyllid make it the perfect carrier of the bacterium. An infected psyllid creates a localized infection when it feeds and transmits the bacterium into a citrus tree. It does not take long for the bacterium to spread throughout the plant, but the inoculum is first concentrated in the leaves and stems where the infected psyllid feeds. Female psyllids lay eggs in the same region where they feed. If these females are infected, their nymphs, which begin feeding in the infected area of the tree when they hatch, eventually acquire the bacterium, molt to the winged adult stage and disperse taking it along with them.

So researchers at the Boyce Thompson Institute, a premier life sciences research institution located in Ithaca, New York on the Cornell University campus, have concentrated their recent efforts on the psyllid itself as a possible link to the control of the disease.

Michelle Cilia, a Research Molecular Biologist at the USDA Agricultural Research Service and Assistant Professor at the Boyce Thompson Institute (BTI), and her team of researchers have been looking at a protein that makes the bellies of citrus psyllids blue and the possible connection it may have with the natural process of spreading the devastating bacterium in the first place. Researchers say Asian citrus psyllids with blue abdomens have high levels of an oxygen-transporting protein called hemocyanin.

According to Cilia, the hemocyanin protein is commonly found in the blood of crustaceans and mollusks. When harboring the bacterium Candidatus Liberibacter asiaticus ( or CLas) the disease is spread by the Asian citrus psyllid. This bacterium force the psyllids to ramp up their production of this protein. Cilia lab scientists, along with colleagues at the University of Washington and the USDA ARS at Fort Pierce, Fla., identified important protein interactions that must occur to perpetuate the transmission of bacterium to new trees.

They examined interactions occurring between the psyllid and the bacterium, and between the psyllid and its beneficial microbial partners. They also compared protein expression levels in both nymphs and adults. Their research shows that adult psyllids appear to mount a better immune response to CLas as compared to nymphs, which may explain why psyllids must acquire CLas during the nymphal stage to efficiently transmit CLas once they become adults.

“For many decades, scientists lacked the ability to look inside insects that transmit plant pathogens and understand what is going on,” said Cilia. “This is no longer true today, thanks to the painstaking work of our collaborators in the Bruce and MacCoss labs at the University of Washington. The new molecular tools developed by our University of Washington colleagues enable us to dissect the vector-pathogen relationship piece by piece to determine which components are important for transmission.”

The group showed that hemocyanin interacts with a CLas protein involved in a vital microbial metabolic pathway called the acetyl-CoA pathway. Scientists have previously targeted this set of biochemical reactions in bacteria when developing antibiotics.

John Ramsey, a USDA ARS postdoctoral associate in the Cilia lab and first author of the study, suspects that the increase in hemocyanin, and the blue color it imparts to the abdomen, could be evidence of an immune response to CLas infection. The findings raise the possibility that this response could be harnessed to help control the bacterium’s spread.

“The study is allowing you to look at your population of insects and say something about the immune system of the insect based on its color,” said Ramsey. “There’s the possibility that this could be a useful part of grove surveillance.”

In future work, the Cilia group plans to test whether there are differences in each color morph’s ability to spread the CLas bacterium. Results from this study will help inform future strategies to control citrus greening disease. Depending on which proteins they decide to target, these new approaches could prevent the psyllid from transmitting CLas or trigger an immune response against the bacterium.

This approach to controlling citrus greening, by blocking bacterial transmission by the psyllid, runs contrary to existing ‘kill the insect’ strategies, said Ramsey. Such an approach may provide a longer lasting solution because the insect isn’t under pressure to evolve to survive the treatment, which commonly occurs with pesticide usage.

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CABI Plantwise Blog

Myzus persicae (green peach aphid); an alate (winged) adult
Myzus persicae (green peach aphid); an alate (winged) adult

Recent research highlights why the green peach aphid (Myzus persicae) is one of the most successful crop pests. These findings will help further the development of effective management and control measures which will ultimately reduce worldwide crop losses.

The green peach aphid is one of the most challenging crop pests, living on hundreds of host plants in over 40 families. This makes it an impressive generalist compared to many other aphids, a large number of which are only adapted to survive on one species. Key crops impacted by this pest include sugar beet, beans, potato, tomato and oilseed rape.

So how can it be such a wide ranging generalist? Recent research, carried out by the Earlham Institute (EI) and John Innes Centre (JIC) in the UK, has found that its ability to survive on so many hosts is largely down to its genetic plasticity (Mathers et al., 2017). After just two days, scientists were able to see that genes responsible for helping aphids adjust to different plants rapidly increased or decreased in activity when an individual was moved to a different host.

Interestingly, it seems that many of the genes involved are not specific to this species of aphid, but that the green peach aphid is just particularly well adapted to adjusting to the expression of the key genes.

Not only can it adapt well to different hosts, the pest transmits over 100 plant virus diseases, including Beet western yellows virus, Bean leaf roll virus and Potato leaf roll virus. Losses caused by these plant diseases can be very high – sugarbeet losses due to beet yellows can be up to 50%. Furthermore, the green peach aphid has developed resistance to over 70 different pesticides, making it difficult to control.

Then there’s its ability to reproduce prolifically. Females can give birth to females without mating with a male (clonal reproduction). Consequently green peach aphids can have up to 30 generations a year (Texas A&M University, 2017).

All in all, it’s no wonder that the green peach aphid is such an incredibly successful pest, unfortunately causing major widespread damage every year. This latest research is a significant step towards understanding how the pest is so successful, paving the way for more effective management and control methods.

For more information, read How to be a successful pest: lessons from the green peach aphid by the Earlham Institute.

You can also find out information regarding the green peach aphid on our Plantwise Knowledge Bank.

CABI, 2017. Green peach aphid (Myzus persicae). In: Plantwise Knowledge Bank. Wallingford, UK: CAB International. http://www.plantwise.org/knowledgebank/datasheet.aspx?dsid=35642

Earlham Institute, 2017. How to be a successful pest: lessons from the green peach aphid. UK: Earlham Institute. http://www.earlham.ac.uk/how-be-successful-pest-lessons-green-peach-aphid

Mathers TC, Chen Y, Kaithakottil G et al., 2017. Rapid transcriptional plasticity of duplicated gene clusters enables a clonally reproducing aphid to colonise diverse plant species. Genome Biology, 18:27.

Texas A&M University, 2017. Green Peach Aphid. In: Texas A&M Agrilife Extension Series. Texas, USA: Texas A&M University. http://texasinsects.tamu.edu/aimg103.html


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