Archive for the ‘Insect-plant interaction’ Category

History And Myth: The Genesis Of Modern-Day Pests

Credit: Flickr

From the Old World to the New, mythologies of origins typically portray the emergence of agriculture as a gift or blessing from benevolent gods, seemingly with one exception. For the Sumerians of the Old World, the earth was barren at first, with humans living in the wilderness foraging for plants, but, signaling civilization’s dawn, well-meaning gods gave plant and animal agriculture to humankind for sustenance. In the New World’s Mesoamerican civilization, Quetzalcoatl — a feathered serpent-god, but sometimes a half-god, half-historical human — gave arts, knowledge, and agriculture to humankind so that humans could leave behind their savage, hunting-gathering ways.

Similar mythologies of origins are common among other ancient peoples around the world. In the Judeo-Christian mythology of western civilization, however, godly retribution for eating the fruit from the tree of knowledge of good and evil led to Adam and Eve’s inevitable adoption of farming when they were banished from paradise: “Cursed is the ground because of you! In toil, you shall eat its yield all the days of your life. (…) By the sweat of your brow, you shall eat bread… .” A partial interpretation of the Judeo-Christian story of agricultural origins is that, compared to our prior condition, procuring sustenance through farming implies substantially altering nature through hard work.

We believe that producing food as we have, especially during the last ~100 years, puts us markedly at odds with nature’s forces, specifically with the ecological and evolutionary forces that underpin nature’s workings. As plants, crops are subject to “rules” set by those ecological and evolutionary forces, and the same applies to all crop associates, such as herbivores and pathogens, and pests and disease organisms. Indeed, a growing body of literature points to the many contradictions between modern agriculture — broadly — on one hand, and ecological and evolutionary rules on the other hand, and to the resulting, unfortunate outcomes. Our own research in pest management, as well as that of others, revealed examples of how from the dawn of agriculture to the present, we created pests from herbivores by ignoring those rules — unknowingly at first, and presently with eyes wide open — in our efforts to produce food to satisfy our demands.

Some of the insect pests that we have studied illustrate how since agriculture’s emergence, evolutionary, ecological, and agricultural processes, from domestication and spread of crops to herbivore host-plant shifts and agricultural intensification, among others, were conducive to transforming some herbivores into crop pests. Such herbivores, we believe, likely were the most-pertinently pre-adapted — as whole species or particular populations of a species — among the herbivores living on (i.e. hosted by) crop wild relatives or associates. We believe, too, that by looking in the past and around us, while armed with modern ecological, evolutionary and genetic insights and tools, we should be able to preempt pests that emerge as agriculture adapts to ongoing climate change.

One of the insect pests that we have studied is corn leafhopper (Dalbulus maidis), the most important sap-sucking (i.e. phloem-feeding) pest of maize (Zea mays mays) in the Neotropics, particularly from Mexico to Argentina and the Caribbean. The corn leafhopper’s native range is in western Mexico, and its ancestral — or original — host plant is Balsas teosinte (Zea mays parviglumis), maize’s immediate ancestor. Maize was domesticated beginning ~9000 years ago within the corn leafhopper’s native range and is the domesticated form of Balsas teosinte. So, as Balsas teosinte was being transformed into maize by ancient Mexicans — a process that required some 5,000 years — it was a predictably easy feat for corn leafhopper to add the new crop to its short list of host plants, which consists exclusively of grasses in the genus Zea, namely a handful of teosintes and maize.

Of the world’s crops, maize is probably the most adaptable to novel environments, a trait that allowed it to spread quickly and widely in the Americas — from today’s southern Canada to Peru and Argentina, and the Caribbean, and from sea level to 4,000 m — before spreading worldwide. Where maize spread in the Americas it was followed by corn leafhopper — except to the crop’s southern- and northernmost distributional limits, where winters are too cold for the insect’s survival. And, as maize was made more productive and maize farming was intensified, the corn leafhopper became a pest.

But, how did corn leafhopper become a pest, given its background as an innocuous herbivore on a wild grass? Dr. Lowell “Skip” Nault — currently Professor Emeritus at The Ohio State University — was the first to begin addressing this broad question. For instance, after numerous studies over decades, he and his students and associates uncovered clear evidence that corn leafhopper indeed co-evolved with maize since its domestication, and that a small set of biological particularities facilitated the herbivore’s transmutation to a pest.

For instance, Nault and his team showed that corn leafhopper was unlike the several other species of Dalbulus leafhoppers on Balsas teosinte and related grasses — ordinary herbivores all — in that it reproduces exclusively on Zea grasses, and overwinters in adult rather than egg stage. Compared to its Dalbulus congeners — all early candidates for occupying maize’s “sap-sucking insect niche” and becoming pests — being a specialist on Zea likely meant that corn leafhopper was near-flawlessly adapted to exploiting maize as it was being tamed into becoming a crop. And, compared too with its Dalbulus congeners, overwintering in the adult stage meant that corn leafhopper would be the first to colonize maize plants as they germinated following the first, early-summer rains.

More recently, our own research added further detail to the story — similar to an impressionist allegory, compiled over decades of research by numerous scientists — of corn leafhopper’s genesis to a maize pest. For instance, we found that corn leafhopper is not a monolithically pestiferous species, but seemingly is divided into two discrete populations, at the least. On one hand, there is a small isolated population of ordinary herbivore individuals living on an equally isolated, near-extinct wild host, perennial teosinte (Zea diploperennis), and, on the other hand, there is a much larger, widespread population of pestiferous individuals living on maize and teosintes everywhere else. Akin to a minute island floating in a vast ocean, corn leafhopper thus seems to consist of a minuscule and isolated population of “wild” individuals embedded within the geography occupied by a large and widespread population of “pestiferous” individuals.

We found too, that if given access, wild corn leafhoppers thrive on maize, as expected if they are to become pests. In this way, it seems plausible that the wild corn leafhoppers may be the remnants of what corn leafhopper was before Quetzacoatl’s bestowal or Adam and Eve’s eviction from paradise. Separately, our research showed also that in transforming Balsas teosinte into maize and improving the crop to produce more grain, ancient farmers and modern crop breeders disarmed today’s maize varieties of their defenses against corn leafhopper, consistent with ecological theory positing that plants can reproduce well or defend well, but cannot simultaneously do both. In an agricultural context, that ecological theory usually means that crops can produce high yields or defend strongly against pests, but cannot do both.

Altogether, Nault’s and our research suggest that in “inventing” — or receiving? — maize and maize agriculture, the New World’s first-farmers, along with their descendants and modern breeders provided an opportunity for a geographically restricted, ordinary herbivore hosted by the ordinary ancestor of a fundamental crop — a pest in-waiting, as it were — to become an important, widespread pest. We are reminded by the small population of wild corn leafhoppers on perennial teosinte that pests are simply herbivores that took advantage of opportunities offered them by agriculture, just as any other herbivore would take an opportunity to do better by itself and its offspring.

Other pest subjects of our research show similar origins. Western corn rootworm (Diabrotica virgifera virgifera), like corn leafhopper, is a maize pest that shifted to maize from one of the crop’s wild relatives— plausibly Chalco teosinte, Zea mays mexicana—and spread and became a pest as maize agriculture was intensified. Unlike corn leafhopper, however, western corn rootworm is the hands-down, single most-important pest of maize in the USA. Also unlike corn leafhopper, western corn rootworm seems to have become a pest coincident with the advent of modern, intensive agriculture, circa the mid-1900s. Our research suggests that with domestication and improvement, maize was disarmed of rootworm defenses— just as it was disarmed of corn leafhopper defenses— though this was evident only through the twentieth century’s first half. However, as maize was being disarmed, it seemingly was gaining tolerance.

Tolerance is a defensive strategy that plants may deploy against herbivores, and in which plants are able to compensate (i.e. recover) growth and reproduction (seed production) lost to herbivores, and in not impacting herbivores IT does not elicit in them an evolutionary counter-response — i.e. herbivores do not respond by overcoming plant tolerance. During the second half of the twentieth century, and coincident with the advent of modern breeding for yield and insect resistance, intensified use of fertilizers and pesticides — including those targeting western corn rootworm — and western corn rootworm’s ascent to pest status, maize seems to have gained in resistance but lost tolerance against the pest.

As a result, today maize seems to be modestly resistant and modestly tolerant to WCR, in other words, it is mostly susceptible to western corn rootworm, and therefore dependent on us for its defense. From our vantage point, it appears that in striving to make maize the most productive among crops — as it indeed is — we traded a plant-based, sustainable corn rootworm defense, tolerance, for human-based defense based on an arsenal of technologies that are poor matches for the insect’s evolutionary potential for adapting to environmental stresses.

Our research continues seeking to better understand how pests come to be, and it includes other pests of New World crops, such as cotton fleahopper, a pest of US cotton, and fall armyworm, a widespread pest of maize. We return to a metaphor used above to point out that our understanding of how natural processes operate, from how a single individual may respond to an environmental stress to the evolution of complex traits in species, can be likened to an impressionist allegory. Impressionist artists — unlike realists, who emphasized truth — composed seemingly unfinished paintings lacking clarity of form and detail, recognizing that the absence of form and detail would be filled by our experiences. Likewise, with our research findings we may assemble descriptions about our subjects of study that contain knowledge gaps, but which may be enhanced with theory and observations to form discernible images, i.e. allegories, of how our subjects come to be or operate.

We end by returning to the question of agricultural origins according to the world’s mythologies. From our pest management perspective, it seems tempting to align with the minority portrayal of agriculture’s birth as retribution rather than a blessing, and consider whether the seeds of today’s pests were sown when agriculture was invented.

These findings are described in the article entitled, Agriculture sows pests: how crop domestication, host shifts, and agricultural intensification can create insect pests from herbivores, recently published in the journal Current Opinion in Insect ScienceThis work was conducted by Julio S Bernal and Raul F Medina from Texas A&M University.


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Field days show Ugandan farmers hope in disease-resistant varieties

By Allison Floyd
University of Georgia, Peanut & Mycotoxin Innovation Lab

Planting an unimproved variety of peanut in Uganda was a recipe for disaster this year. Groundnut rosette disease (GRD), an aphid-borne virus that causes mottling and affects much of sub-Saharan Africa, took 80% to 100% of the yield in some fields planted with a traditional variety.

The difficult season made farmers even more interested in two recent field-day events held in Uganda, where they could see the results coming from fields planted with improved varieties resistant to GRD.

Farmers check out peanut-growing guides at one of two recent Field Day trainings in Uganda.

One woman, a farmer named Adong Christine borrowed $7,000 from a bank and planted 20 acres with a local variety. At the end of the season, she harvested just two bags of peanuts (from a potential 400 bags) and could not repay the loan.

“There had been an outcry of big losses as most of the capital were borrowed from loan institutions. This event showcasing improved groundnut varieties therefore was timely as it restored hopes and enhanced adoption,” organizers said.

David Okello, the head of Uganda’s national groundnut research program and a leading scientist on PMIL’s breeding project, is behind many of the varieties. Based at the National Semi-Arid Resources Research Institute (NaSARRI) in Serere District, Okello works to create varieties that are high yielding, resistant to drought and GRD, and to educate farmers about practices that will give them more success with their peanut crop.

Peanuts are a traditional crop in Uganda and much of sub-Saharan Africa, are high-protein and valuable as a cash crop. Still, GRD is a persistent problem that stunts the growth of otherwise healthy plants and can destroy a crop if the disease strikes early enough in the season before flowering.

A woman farmer picks up some bags of seed at Field Days in the Nwoya District of Uganda. At the end of a particularly bad season for disease, many farmers made the investment to buy small bags of improved seed.

At one of two field days, 61 farmers, researchers and representatives of local government visited a 5.6-acre plot planted with three varieties bred for their resistance to GRD and leaf-spot, Serenut 9T (Aber), Serenut 14R and Serenut 5R. While participants could see for themselves the success of the varieties, farmers in the Loyo Kwo group, who are using the new varieties, explained their agronomic practices, where they get seed and how NaSARRI trainings helped improve their results.

“Heart breaking and sad testimonies came from the farmers growing local varieties,” Okello said. “The Loyo Kwo group members, on the other hand, were boasting of bumper harvests, higher income and improved livelihoods that they are experiencing from adopting the improved groundnut varieties,” Okello  said

Uganda Field DaysLeoora Okidi (centre) shows her approval of the high yield of Serenut 11T, an improved variety during a Field Day in August 2017 in the Kiteny Pader District of Uganda.


Farmers were able to buy small packs of .5 kg to 3 kg., and the NaSARRI team delivered 45 kgs of Serenut 8R (Achieng), a large-seeded red variety that had been previously promised.

In a second field day, farmers spent part of a religious holiday – the Assumption of the Virgin Mary to Heaven – visiting test plots, learning about improved production practices and visiting a farm where the owner planted Serenut 5R and Serenut 11T alongside the local Red Beauty variety.

Uganda Field Days crowdA crowd of farmers fan out over a field at a recent Field Days event comparing the yield and disease resistance of improved lines and varieties over the traditional, unimproved types, which have been ravaged by rosette disease this year.


The farmer, Leonora Okidi, planted 2 of her 5 acres with an improved variety, and the other 3 acres with the local variety. She abandoned the local variety after the first weeding since most of the plants had been severely attacked by the rosette virus.

In a good year, she is able to feed and educate her 11 own children and support 25 others from her groundnut operation, which is part of a women-led group called Pur Lonyo or “Farming is Wealth,” she said.

Okidi first connected with Okello through her son, who he mentored in his diploma and bachelor’s degree studies and still supervises in his current master’s degree studies. She offered land to host demonstration plots and participatory variety trials and co-funded the operations using her family labour.

“The superiority of our improved lines and varieties over her local varieties caught her attention and (Okidi) quickly adopted these improved varieties and has become a model research farmer in the village,” Okello said. “Through this effort our improved varieties adoption rates has increased and we are closely working with her women group to upscale these successes, improve their livelihoods and increase varieties adoption.”

– Published Sept. 1, 2017

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This issue of the icipe e-bulletin includes, amongst others, an excellent article on ‘Invasive species in Africa‘ by Dr. Segenet Kelemu, Director General, icipe  and on the invasive fall armyworm, Spodoptera frujiperda, by IAPPS East Africa Regional Coordinator, Dr. Tadele Tefera.

To view the bulletin click on the url below:

Click to view: icipe e-bulletin – Volume 7, Issue No. 2, 2017 (pdf)

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SE farm press


Some peanut plants pass ‘memory’ of stress to next generation

Several studies of seed quality, seedling development, and vigor conducted by researchers at the University of Florida suggest that a “memory” of stress events in plants can be passed on to the next generation.

Kelly Arquette, Diane Rowland, Barry Tillman | Apr 18, 2017

For as long as crops have been domesticated, farmers have been selecting seed from the best performing plants; based primarily on their yield and relative performance. In some cases, a plant may experience stress during the season, whether from disease, drought, or insects.

Many times that plant will recover and still produce a decent yield, and possibly provide seed for planting the following year. It’s a system that has worked relatively well for a long time. But this system depends on the idea that if a plant experiences stress and survives, it won’t pass a memory of the stress on to its offspring. Farmers and researchers have made the assumption that the impacts of stress on a plant remain in the current generation and don’t make an imprint into the next generation. But recent research suggests that this might not be true.

Several studies of seed quality, seedling development, and vigor conducted by researchers at the University of Florida suggest that a “memory” of stress events in plants can be passed on to the next generation. In these studies, some varieties of peanut, for example, TUFRunner ‘511’ showed an increased rate of establishment and root growth when their parents had experienced a mild water stress, even when the next-generation seedlings themselves were well-watered.

Figure 1: Peanut root bioassay for early germination and root establishment for seed produced from parent plants that had experienced a mild drought stress during the season and for seed from parents that had not experienced any stress. The left hand panel clearly shows faster and more extensive root growth in offspring from stressed parents over a 12 day span (DAP = Days After Planting). Photo credit: Kelly Racette.

However, other varieties (C7616) displayed the opposite trend; seedlings had improved establishment and root growth when their parents had been well-watered. To complicate matters even further, a third set of varieties, including the Spanish-type variety, COC041, showed no evidence of stress memory in their offspring at all.

The presence of either a positive or negative memory in crop plants could have big implications for seed production. For example, if exposing parent plants to some degree of stress increased seed quality of the next generation, through improved germination and establishment, it may be useful to produce seed under mildly stressful conditions for these varieties. On the other hand, growing varieties that have poor seedling performance from stressed parent plants would require more careful management for seed production to get the best quality seed.

Before recommendations can be refined based on generational stress memory for the production of seed peanuts, further research is being conducted to find out which varieties of peanut display this “memory” and what other impacts stress could have on seed quality.

Currently, studies are being done on other Spanish- and runner-type varieties, like FloRun ‘107’ and New Mexico Valencia C. This additional information is critical to “fine tune” the ideal conditions for each variety during seed production to maximize the quality of seed essential for optimal germination and stand establishment. This research also extends and highlights how important optimal crop management is because decisions within a season could be impacting the next generation.

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Western Corn Rootworm adults Purdue Extension Entomology – Purdue University
The western corn rootworm was first classified as a corn pest in the 1860s. Shown here are adults.

Fighting world hunger: Researchers use nuclear methods to study pest resistance in corn plants

Expertise, resources found at the University of Missouri allow researchers to study pest-resistance in corn that could help sustain projected 9 billion global population.

Jeff Sossaman | Mar 10, 2017

Developing corn varieties that are resistant to pests is vital to sustain the estimated 9 billion global population by 2050.

Now, researchers at the University of Missouri, using advanced nuclear methods, have determined the mechanisms corn plants use to combat the western corn rootworm, a major pest threatening the growth of the vital food source.

Scientists believe that using the knowledge gained from these cutting-edge studies could help crop breeders in developing new resistant lines of corn and make significant strides toward solving global food shortages.

“The western corn rootworm is a voracious pest,” said Richard Ferrieri, a research professor in the MU Interdisciplinary Plant Group, and an investigator at the MU Research Reactor (MURR).

“Rootworm larvae hatch in the soil during late spring and immediately begin feeding on the crop’s root system. Mild damage to the root system can hinder water and nutrient uptake, threatening plant fitness, while more severe damage can result in the plant falling over.”

Breeding corn that can fight these pests is a promising alternative. Ferrieri, and his international team of researchers, including scientists from the University of Bern in Switzerland, Brookhaven National Laboratory in New York and the U.S. Department of Agriculture, used radioisotopes to trace essential nutrients and hormones as they moved through live corn plants. In a series of tests, the team injected radioisotope tracers in healthy and rootworm-infested corn plants.


“For some time, we’ve known that auxin, a powerful plant hormone, is involved in stimulating new root growth,” Ferrieri said. “Our target was to follow auxin’s biosynthesis and movement in both healthy and stressed plants and determine how it contributes to this process.”

By tagging auxin with a radioactive tracer, the researchers were able to use a medical diagnostic imaging tool callED positron emission tomography, or PET imaging, to “watch” the movement of auxin in living plant roots in real time.

Similarly, they attached a radioactive tracer to an amino acid called glutamine that is important in controlling auxin chemistry, and observed the pathways the corn plants used to transport glutamine and how it influenced auxin biosynthesis.

The researchers found that auxin is tightly regulated at the root tissue level where rootworms are feeding. The study also revealed that auxin biosynthesis is vital to root regrowth and involves highly specific biochemical pathways that are influenced by the rootworm and triggered by glutamine metabolism.

“This work has revealed several new insights about root regrowth in crops that can fend off a rootworm attack,” Ferrieri said. “Our observations suggest that improving glutamine utilization could be a good place to start for crop breeding programs or for engineering rootworm-resistant corn for a growing global population.”


Ferrieri’s work highlights the capabilities of the MURR, a crucial component to research at the university for more than 40 years. Operating 6.5 days a week, 52 weeks a year, scientists from across the campus use the 10-megawatt facility to not only provide crucial radioisotopes for clinical settings globally, but also to carbon date artifacts, improve medical diagnostic tools and prevent illness.

MURR also is home to a PETrace cyclotron that is used to produced other radioisotopes for medical diagnostic imaging.

The study, “Dynamic Precision Phenotyping Reveals Mechanism of Crop Tolerance to Root Herbivory,” was published in Plant Physiology.

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New York Times


Cherry tomatoes. Researchers found that domesticated tomatoes like these were less resistant to whiteflies than currant tomatoes, a wild species. Credit Dean Fosdick/Associated Press

Whiteflies are the scourge of many farms, damaging tomatoes, peppers, eggplants and other crops. Now, researchers in Britain report that a species of wild tomato is more resistant to the pest than its commercial counterparts.

The wild type, the currant tomato, is closely related to domestic varieties, “so we could crossbreed to introduce the resistance,” said Thomas McDaniel, a biologist and doctoral student at Newcastle University in England and a co-author of the study, published in the journal Agronomy for Sustainable Development. “Another method would be genetic engineering, if we identified the genes.”

The researchers studied Trialeurodes vaporariorum, a species of whitefly that often attacks tomatoes grown in greenhouses. Whiteflies damage tomato plants by extracting the plant’s sap, which contains vital nutrients; by leaving a sticky substance on the plant’s surface that attracts mold; and by transmitting viruses through their saliva.

But currant tomatoes have some sort of mechanism, yet to be understood, that repels whiteflies. “They seemed to move away every time they tried to sample the sap,” Mr. McDaniel said.

The wild plants also produce a chemical reaction that causes the plant sap to gum up the whitefly’s feeding tube.

Growers use a parasitic wasp to control whiteflies. The wasp lays its eggs on young whiteflies, which are eaten by hatching larvae. The treatment is expensive and laborious. As an alternative, farmers use chemical pesticides, but some have been linked to declines in bee populations.

“Genetic diversity is very, very low in domestic crops, so introducing these genes that we’ve lost along the way is probably quite important,” Mr. McDaniel said.

Continue reading the main story


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PiercesDiseasePierce’s disease on grape


Newly identified enzyme may be the culprit in Pierce’s disease grapevine damage
January 12, 2016

Printable version


An enzyme appears to enable Xyllela fastidiosa bacteria to infect grapevines with Pierce’s disease, causing serious leaf damage. UC Davis plant scientists have identified an enzyme that appears to play a key role in the insect-transmitted bacterial infection of grapevines with Pierce’s disease, which annually costs California’s grape and wine industries more than $100 million.
The researchers hope that the discovery, which runs counter to existing theories, will lead to new diagnostics and potential treatments for Pierce’s disease. Their findings are reported in Scientific Reports, an online journal of the Nature Publishing Group.
“With a bacterial disease — much like cancer — if you understand how the virulent form spreads, you can better control or remove it, ” said Abhaya Dandekar, a professor of plant sciences and senior author on the study.
“We anticipate that this discovery could open new ways to think about dealing with Pierce’s disease and highlight other areas of immune response, in general, that haven’t yet been considered,” he said.
About Pierce’s disease
Pierce’s disease, first identified in the 1890s, is caused by the bacterium Xylella fastidiosa and is characterized by yellowed and browning leaves that eventually drop from the vine. The disease is transmitted from vine to vine by small, winged insects called sharpshooters.
Pierce’s disease is established in Northern California, where it is transmitted by the blue-green sharpshooter, which lives near rivers and streams. The disease became a serious threat to California agriculture in 1996 when the glassywinged sharpshooter — another Pierce’s disease carrier native to the Southwest — was discovered in the Temecula Valley of Southern California.
How infection progresses
It’s been known for a number of years that when Xyllela fastidiosa invades a grapevine, it produces a biofilm or gel in the xylem — the vascular tissue that transports water and some nutrients throughout the vine.
Scientists have theorized that this biofilm damages the vine by clogging up the xylem, preventing the flow of water to the leaves. That theory seemed to explain the yellowing of the leaf edges and eventual death of the leaf tissue.
But not all of the evidence stacked up to fit that theory, Dandekar said. For example a heavy accumulation of Xyllela fastidiosa in grapevine leaves was not always accompanied by severe disease symptoms in leaves. And, in some infected grapevines as well as other host plants, the leaves showed severe symptoms but the xylem had very little blockage.
So Dandekar and colleagues set out to investigate an alternative mechanism by which Xyllela fastidiosa might be wreaking havoc with the vine’s physiology.
Secrets of the “secretome”
The research team began by analyzing the bacteria’s secretome — the entire collection of enzymes and other proteins secreted by a disease-causing agent like Xyllela fastidiosa during the infection process. Such secreted proteins are known to play key roles in triggering many plant diseases.
The resulting data indicated that an enzyme, which the researchers named LesA, was quite abundant during Xyllela fastidiosa infections and shared characteristics with similar enzymes known to be capable of breaking down plant cell walls.
The researchers went on to confirm their suspicions by demonstrating that a mutant strain of Xyllela fastidiosa bacteria — with a specific gene knocked out, or inactivated — lacked the ability to cause infection in grapevines.
“The LesA enzyme has the ability to move through cell membranes, equipping the Xyllela fastidiosa bacteria to invade the grapevine and to live in its xylem tissues, where it feeds on fatlike compounds called lipids,” Dandekar says.
In this way, the LesA enzyme triggers the process that causes the typical Pierce’s disease leaf damage — a process completely unrelated to the xylem blockage and water stress that had previously been thought to cause the symptomatic leaf damage.
The research for the newly published study was conducted by Rafael Nascimento and Hossein Gouran, both graduate students in Dandekar’s laboratory. Dandekar said that his research team plans to move forward with Pierce’s disease research in hopes of developing ways to counteract the disease.

Funding for the newly published study was provided by the Pierce’s Disease Board of the California Department of Food and Agriculture.
Additional information:
• Related: Fused genes tackle deadly Pierce’s disease in grapevines
• Related: UC Davis cracks the walnut genome
• Related: Springtime for wheat starts with a gene that ‘sees’ light
Media contact(s):
• Abhaya Dandekar, Plant Sciences, (530) 752-7784, amdandekar@ucdavis.edu
• Pat Bailey, UC Davis News Service, (530) 752-9843, pjbailey@ucdavis.edu

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Released: 26-Apr-2015 7:00 PM EDT
Source Newsroom: Cardiff University

Newswise — Scientists may have uncovered a natural way of avoiding the use of pesticides and helping save plants from attack by recreating a natural insect repellent.
Scientists from Cardiff University and Rothamsted Research have, for the first time, created tiny molecules which mirror a natural occurring smell known to repel insects.
The scientists were able to make similar smelling insect repellent molecules, by providing the enzyme, ((S)-germacrene D synthase), which creates the smell, with alternative substrate molecules.
The effectiveness of the smell or perfume to function as an insect repellent was tested.
The team found that the smells repelled insects but in one case a reversal of behaviour – an attractant – was observed which raises the prospect of being able to develop a trap-and-kill device.
“We know that many organisms use smell to interact with members of the same species and to locate hosts of food or to avoid attack from parasites,” according to Professor Rudolf Allemann from Cardiff University’s School of Chemistry, who led the research.
“However, the difficulty is that scientifically smell molecules are often extremely volatile, chemically unstable and expensive to re-create. This means that, until now, progress has been extremely slow in recreating smells that are similar to the original.
“Through the power of novel biochemical techniques we have been able to make insect repellent smell molecules which are structurally different but functionally similar to the original,” he added.
Pesticides are toxic by design and are used widely to kill, reduce or repel insects, weeds, rodents, fungi or other organisms that can threaten public health and the economy.
Many concerns have been raised on the potential dangers to humans and the impact on the environment and local ecosystem.
Professor John Pickett, FRS from Rothamsted Research said: “This is a breakthrough in rational design of smells and provides a novel way of producing a smell with different properties and potentially better ones than the original but at the same time preserving the original activity.
“By using alternative substrates for the enzymes involved in the ligand biosynthesis (biosynthesis of the smell) we can create the appropriate chemical space to reproduce, with a different molecular structure, the activity of the original smell.”
The team hope that their research could provide a new way of designing and developing small smell molecules which would be otherwise be too difficult to produce by usual scientific and commercial methods.

Touchet et al., Novel olfactory ligands via terpene synthases (DOI: 10.1039/c5cc01814e) was funded by the BBSRC and published in the journal Chemical Communications.
Further information or to arrange media interview, please contact:
Chris Jones
Communications and Marketing
Cardiff University
Tel: 029 20 874731
E-mail: jonesc83@cardiff.ac.uk
Cardiff University
Cardiff University is recognized in independent government assessments as one of Britain’s leading teaching and research universities and is a member of the Russell Group of the UK’s most research intensive universities. Among its academic staff are two Nobel Laureates, including the winner of the 2007 Nobel Prize for Medicine, University Chancellor Professor Sir Martin Evans. Founded by Royal Charter in 1883, today the University combines impressive modern facilities and a dynamic approach to teaching and research. The University’s breadth of expertise encompasses: the College of Arts, Humanities and Social Sciences; the College of Biomedical and Life Sciences; and the College of Physical Sciences, along with a longstanding commitment to lifelong learning. Cardiff’s four flagship Research Institutes are offering radical new approaches to cancer stem cells, catalysis, neurosciences and mental health and sustainable places.

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IMustapha KSU248hessfly_adultHessian Fly

Mustapha El-Bouhssini (MS ’86, PhD ’92) Aleppo, Syria, is a global authority on plant resistance to insects in grains and has worked to develop crop varieties resistant to several important arthropod pests.

He recently received the Distinguished Scientist Award from the International Branch of the Entomological Society of America for significant contributions to entomological research.

El-Bouhssini serves as an adjunct faculty member in the Department of Entomology. This position has helped initiate collaborative projects between K-State and ICARDA on Hessian fly genetics and resistance in barley to the Russian wheat aphid.

From the KSU AgReport Spring 2015

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BLACKSBURG, Va., Aug. 22, 2014 – An invasive weed poses a serious and frightening threat to farming families in Ethiopia, but scientists from a Virginia Tech-led program have unleashed a new weapon in the fight against hunger: a tiny, speckled beetle.

The weed, called parthenium, is so destructive that farmers in the east African nation have despairingly given it the nickname “faramsissa” in Amharic, which, translated, means “sign your land away.” Farmers have doused the weed in pesticides and ripped it out with their hands, but it has only spread further.

After a decade-long effort, scientists from the Integrated Pest Management Innovation Lab released a parthenium-eating beetle called Zygogramma bicolorata.

“Extensive research has shown us that the beetle eats and breeds only on parthenium leaves,” said Muni Muniappan, director of the Integrated Pest Management Innovation Lab, a program funded by the U.S. Agency for International Development. “It’s been tested in Australia, India, South Africa, and Mexico with similar results.”

Parthenium is native to the Americas, where a suite of natural enemies that includes the Zygogramma beetle keeps the weed in check. But in the early 1970s, parthenium entered Ethiopia in shipments of food aid from the United States. With no serious contenders, the plant flourished.

In the past three decades, parthenium has become the second most common weed in Ethiopia, suppressing the growth of all other plants and wreaking havoc in the fields and gardens of smallholder farmers.

“The plant is an aggressive invader. A single plant can produce 25,000 seeds and completes its life cycle in six to eight weeks,” said Wondi Mersie, a Virginia State University professor and principal investigator of the Virginia Tech-led project. “It displaces native species, affects human health, and negatively impacts quality of life.”

Parthenium is poisonous. People who come into contact with it can suffer from skin irritations, bronchial asthma, and fever. Animals that eat it can experience intestinal damage, and their milk and meat becomes bitter and useless.

The Innovation Lab built a quarantine facility in 2007 to ensure that the pea-sized beetle had eyes for parthenium alone. Testing under quarantine is one of the crucial steps involved in biological control, a rigorously tested method where an invasive species’ natural enemies are used to regulate it.

“Opportunities for biocontrol in Ethiopia are huge, and there would be enormous benefits,” said Arne Witt, a biologist not associated with the Virginia Tech program who works with UK-based nonprofit CABI.

After a laborious process involving many agencies and much red tape, Zygogramma bicolorata was approved for release. Researchers collaborated with farmers, local government officials, and extension agents to construct a breeding facility and increase the number of beetles.

Finally, on July 16, the Innovation Lab team joined a group of about 30 scientists and farmers in Wollenchitti, Ethiopia, to release the insects. The group moved from parthenium patch to parthenium patch, dumping beetles from containers.

Ethiopian researchers will monitor the sites and assess the impact. As a second step, scientists are poised to release a stem-boring weevil that will join Zygogramma. But even these measures will not eliminate parthenium from Ethiopian farmland.

“Biocontrol is control, not eradication,” said Witt. “But it means that a farmer sprays less pesticide. We need an integrated strategy, and biological control is the most cost-effective strategy – let’s embrace it.”

The Integrated Pest Management Innovation Lab is managed by the Office of International Research and Education at Virginia Tech.

Dedicated to its motto, Ut Prosim (That I May Serve), Virginia Tech takes a hands-on, engaging approach to education, preparing scholars to be leaders in their fields and communities. As the commonwealth’s most comprehensive university and its leading research institution, Virginia Tech offers 225 undergraduate and graduate degree programs to more than 31,000 students and manages a research portfolio of $496 million. The university fulfills its land-grant mission of transforming knowledge to practice through technological leadership and by fueling economic growth and job creation locally, regionally, and across Virginia.

Written by Kelly Izlar

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