Archive for the ‘Research’ Category

Nematode pheromone ascr#18 has been shown to alert plants to the presence of plant-parasitic nematodes and to activate their immune responses.

Nematodes, or roundworms, are the most numerous animals on earth, parasitizing most plants and animals. These infections are responsible for many of the most common neglected tropical diseases, causing significant morbidity and mortality. Soil-dwelling nematodes also put food security at risk by attacking agriculturally important plants. While the human response to dealing with parasite infection has been thoroughly researched; it has only recently been discovered that plant-parasitic nematodes not only activate defensive responses in plants, but also provide nematode-mediated immunity to subsequent attack by pathogens and viruses.

Numerous nematodes

Root-knot nematode galls on plant roots. Source: commons wikimedia
Root-knot nematode galls on plant roots. Source: commons wikimedia

Despite more than 4,100 species of plant-parasitic roundworms being identified, two major groups of nematodes are responsible for most agricultural plant damage. The root-knot nematodes, Meloidogyne spp. damage plants by producing galls on roots; whereas, the cyst nematodes, Heterodera and Globodera spp., by the formation of root cysts.

Soil-dwelling nematodes are ubiquitous and rich arable soil may contain up to 3 billion worms per acre. It therefore comes as no surprise that infected crops result in over $100 billion worth of agricultural damage globally per annum. For British crops alone, damage by cyst nematodes, Globodera rostochiensis and G. pallida, account for an estimated  £50 million damage each year.

Cyst nematodes damage to potato roots. Source: commons wikimedia

Cyst nematodes damage to potato roots. Source: commons wikimedia

Nematode control therefore is a serious business; however, following the current tightening of legislation, withdrawal from use of inorganic pesticides (the primary source of pest and disease management over the past decades) and a lack of resistant plant varieties, there is an urgent need to understand more about plant natural defenses to promote resistance to nematodes and other invaders.

Plant defenses against pathogens

Plant defenses can be broadly grouped into constitutive (continuous) defenses and inducible defenses. Toxic chemicals or defense-related proteins are typically only produced after pathogens are detected due to the high energy costs associated with their production and maintenance. To allow detection of, and rapid response to, potentially harmful pathogens plants have evolved several layers of highly developed surveillance mechanisms to try and circumvent serious damage.

The first line of defense consists of inducible defenses, which are mounted when plant cells recognize microbe-associated molecular patterns (MAMPs), such as lipopolysaccharides, flagellin, peptidoglycan and other compounds commonly found in microbes. Plant cells then become fortified against attack, conferring protection from the invading pathogen. Although MAMP’s have been well characterized, up until recently, it remained unclear as to whether plants could detect conserved molecular patterns derived from plant-parasitic animals, such as soil-dwelling nematodes.

‘Nematode-associated molecular patterns’

A number of studies have previously shown that, in response to plant-parasitic nematode infection, plants quickly activate defense pathways similar to those induced by other pathogens. Although these findings were very promising, what the nematode-derived signals actually were remained a mystery.

Following the discovery that non-parasitic soil nematodes can also induce plant defenses, a conserved nematode signature molecule appeared to be a likely trigger for activating the plant defense response. Ascarosides are pheromones exclusive to nematodes that are used to regulate development and social behaviours. Ascarosides represent an evolutionarily conserved family of signalling molecules, of which more than 200 different ascaroside structures from over 20 different species have been identified. Due to the highly conserved nature of these molecules, it seemed plausible that plant hosts and nematode-associated microorganisms may have evolved the means to detect and respond to this ancient nematode molecule. A recent study published in Nature Communications investigated whether ascarosides can be detected by plants, and whether detection of the molecules induced the plant-defence response.

(a) Examples of ascarosides previously identified. (b) HPLC-MS analysis of nematode exo-metabolome samples, showing seven detected ascarosides. (c) Chemical structures of identified ascarosides and relative quantitative distribution. Source: http://www.nature.com/ncomms/2015/150723/ncomms8795/fig_tab/ncomms8795_F1.html
(a) Examples of ascarosides previously identified. (b) HPLC-MS analysis of nematode exo-metabolome samples, showing seven detected ascarosides. (c) Chemical structures of identified ascarosides and relative quantitative distribution. Source: http://www.nature.com/ncomms/2015/150723/ncomms8795/fig_tab/ncomms8795_F1.html

Profiles of ascarosides from adult and juvenile stages of a number of agriculturally relevant species of plant-parasitic nematodes were characterised using mass spectrometry (MS) to analyse the metabolome excreted into media supernatant. MS analysis of exo-metabolome samples revealed excretion of similar sets of ascarosides in all analysed species; however, ascr#18 was identified in all plant-parasitic nematodes as the most abundant molecule.

In order to determine whether ascr#18 could be perceived by plants and influence plant-defensive responses to different pathogens, the ascaroside was applied in various concentrations to Arabidopsis roots 24 h prior to leaf innoculation with pathogens. By monitoring expression of MAMP-triggered immunity (MTI) markers and defense-related genes in leaves at different time points after root treatment with ascr#18, characteristic defense responses such as MAMP-triggered immunity were shown to be induced. Interestingly, local and systemic defenses were also shown to be activated by ascr#18 application to leaves.

Detection of ascr#18 by plants increased resistance to viral, bacterial, oomycete, fungal and nematode infections in Arabidopsis, as well as tomato, potato and barley. Additionally, three other ascarosides applied to different plants showed defense responses were induced by structurally diverse ascarosides, but that this varied in a structure- and species-dependent manner.


A comparison of experimental wheat lines showing different levels of resistance to the disease spot blotch. Source: https://www.flickr.com/photos/cimmyt/6508078617
A comparison of experimental wheat lines showing different levels of resistance to the disease spot blotch.                                                                                                                                                                                                                                                                            Source: https://www.flickr.com/photos/cimmyt/6508078617

Plant crops suffer  considerable damage every year from parasites and pathogens, putting food security at great risk. The ability to activate plant immune responses as and when required by using signalling molecules, such as ascarosides, is an exciting discovery that could contribute to improving the economic and environmental sustainability of agriculture. One potential application could be spraying of ascr#18 on crop leaves; as although plants primarily encounter ascarosides via their roots, leaf exposure to low ascr#18 concentrations was also effective at inducing the defense responses to confer fortification against attack.

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planthopper_SmallOne of the leading pests of rice, brown planthoppers can grow up to have either short or long wings, depending on conditions such as day length and temperature in the rice fields where they suck sap. The hormone insulin controls the switch that tells young planthoppers whether to develop into short- or long-winged adults, finds a new study. Photo by Chuan-Xi Zhang of Zhejiang University in China

Insulin tells young planthoppers whether to develop short or long wings

DURHAM, NC – Each year, rice in Asia faces a big threat from a sesame seed-sized insect called the brown planthopper, Nilaparvata lugens. Now, a study reveals the molecular switch that enables some planthoppers to develop short wings and others long — a major factor in their ability to invade new rice fields.

Lodged in the stalks of rice plants, planthoppers use their sucking mouthparts to siphon sap. Eventually the plants turn yellow and dry up, a condition called “hopper burn.”

Each year, planthopper outbreaks destroy hundreds of thousands of acres of rice, the staple crop for roughly half the world’s population.

The insects have a developmental strategy that makes them particularly effective pests. When conditions in a rice field are good, young planthoppers develop into adults with stubby wings that barely reach their middles.

Short-winged adults can’t fly but they’re prolific breeders. A single short-winged female can lay more than 700 eggs in her lifetime.

“The short-winged ones have great big fat abdomens. They’re basically designed to stay put and reproduce,” said biologist Fred Nijhout of Duke University, who co-authored the study with colleagues at Zhejiang University in China.

But in the fall as days get shorter and temperatures begin to drop — signs that the rice plants they’re munching on will soon disappear — more planthopper nymphs develop into slender adults with long wings. Long-winged planthoppers lay fewer eggs but are built for travel, eventually flying away to invade new rice fields.

Until now, scientists did not know exactly how the shorter days and cooler temperatures triggered the shift between short and long wings, or which hormones were involved.

To find out, the researchers used a technique called RNA interference (RNAi) to silence the genes for two different insulin receptors — regions on the cell membrane that bind to the hormone insulin — and measured the effects on the animals’ wings.

“Previously it had been assumed that all insects only had a single insulin receptor gene. We discovered that brown planthoppers have two,” Nijhout said.

When the researchers silenced the first insulin receptor, short-winged adults emerged. Silencing the second receptor produced adults with long wings.

Further study revealed that long wings are the default design. But when planthoppers secrete a particular type of insulin in response to changing temperatures or day length, the second insulin receptor deactivates the first receptor in the developing wings, leading to short-winged adults.

“The second insulin receptor acts by interfering with the first one, therefore shutting down the signal,” Nijhout said.

It’s too early to say whether the findings could lead to techniques to treat planthopper populations so they are unable to invade new rice fields, Nijhout says.

But the researchers have found similar mechanisms in other planthopper species, and are now trying to find out if insulin plays a similar role in other insect pests with flying and flightless forms, such as aphids.

This research was supported by the National Basic Research Program of China (973 Program, no. 2010CB126205) and by the National Science Foundation of China (no. 31201509 and no. 31471765).


The appeared Mar. 18 in the journal Nature.

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Colo pot beetle rnaiThe Colorado potato beetle, also known as an international super pest, munches on a potato plant leaf.
Credit: MPI for Molecular Plant Physiology and MPI for Chemical Ecology


Insecticides: Researchers stop the Colorado potato beetle in its tracks by preventing the insect from synthesizing essential proteins
By Sarah Everts
Department: Science & Technology
News Channels: Biological SCENE, Environmental SCENE


The Colorado potato beetle, also known as an international super pest, munches on a potato plant leaf.
Credit: MPI for Molecular Plant Physiology and MPI for Chemical Ecology
The Colorado potato beetle costs the agricultural industry billions of dollars per year and devours so many crops around the world that the insect has been branded an “international super pest.” Because the pest has become resistant to all major classes of insecticides and has few natural enemies, crop scientists are seeking a strategy to rein in the beetle’s feeding frenzies.
A team of researchers led by Ralph Bock at the Max Planck Institute for Molecular Plant Physiology, in Potsdam, Germany, now reports that it has found a way to protect crops from the Colorado potato beetle with a new insecticidal tool: RNA interference, or RNAi (Science 2015, DOI: 10.1126/science.1261680).
To use RNAi against the pest, the researchers first identified a gene the insect can’t do without—one that encodes a cytoskeleton protein vital to maintaining a cell’s shape. Researchers then engineered vulnerable plants to produce a custom double-stranded RNA. As the insect pest dines on the plant, the double-stranded RNA gets converted into small interfering RNA. These fragments prevent the insect’s ribosome from reading the messenger RNA for the essential protein. The obstruction blocks production of the essential protein, and the insect dies.
The inspiration to use RNAi to kill pests dates back nearly a decade, says Jiang Zhang, the study’s first author.
Although the RNAi strategy was implemented in plants years ago, it failed as a powerful insecticide because the pests didn’t all die, explains Steve Whyard, at the University of Manitoba, in Winnipeg, in an associated commentary (Science 2015, DOI: 10.1126/science.aaa7722). Bock, Zhang, and their colleagues, however, have now made a “clever modification” to the earlier, partially successful strategy, Whyard notes, by inserting the instructions to make the double-stranded insecticidal RNA into plant cells’ chloroplasts, instead of into their nuclei. The result of putting the insecticidal RNA into chloroplasts, a plant’s photosynthesis hot spot, was full crop protection from the Colorado potato beetle.
Previous attempts probably didn’t work well because the cytoplasm within plant cells has machinery that metabolizes double-stranded RNA before pests such as the Colorado potato beetle can consume it. Conversely, chloroplasts have no machinery to metabolize double-stranded RNA, allowing the insecticidal molecules to accumulate and be stored until a pest dines on the plant.
One general benefit of the RNAi approach, Zhang says, is that researchers can selectively target specific insect pests by targeting species-specific gene sequences; this avoids the blanket destruction of other insect species seen with many insecticides, he explains.
Whether the new approach will work on other insect pests is an open question, comments Niels Wynant, who studies pest control at KU Leuven, in Belgium. And it remains to be seen how quickly pests will develop resistance mechanisms to the RNAi insecticides. That being said, Wynant adds, the findings could have a “significant impact” on pest control strategies and should be further investigated by agricultural companies.

Chemical & Engineering News
ISSN 0009-2347
Copyright © 2015 American Chemical Society

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Pesticides just got a whole lot smaller. Is that a good thing?

By Liz Core on 22 Jan 2015

Nanoparticles are basically the X-Men of the molecular world, in that they are unpredictable, elusive, and come in a dizzying array of forms.

So it should come as no surprise that scientists are now researching a new type of nanotechnology that could revolutionize modern farming: nanopesticides. Recent studies have suggested that the nano-scale pesticide droplets could offer a range of benefits including raising crop durability and persistence, while decreasing the amount of pesticide needed to cover the same amount of ground. But they’re also looking at the hefty potential for trouble: No one knows if the nanopesticide particles will seep into water systems, and, if they do, if they will harm non-pests like bees, fish, and even humans.

As we’ve written before, nanotechnology involves engineering particles that are tinier than the tiniest tiny. (More technically, we’re talking anything measured in billionths of a meter.) Scientists find this useful, since most substances behave much differently at that scale. Already, nanotechnology has changed the medical world, with nanoparticles used to purify water, protect against UV rays, and detect contamination.

The same could be true in farming. By shrinking the size of pesticide droplets down to nano-scale, scientists could help decrease overall pesticide use in U.S. agriculture. Which is a big thing — although we’ve come down a bit from the pesticide heyday of the 1980s, we still poured out 516 million pounds of pesticides in 2008 alone. Yipes. Here’s more on the potentially game-changing tech, from Modern Farmer:

By shrinking the size of individual nanopesticide droplets, there is broad consensus — from industry to academia to the Environmental Protection Agency — that the total amount of toxins sprayed on agricultural fields could be significantly reduced. Smaller droplets have a higher total surface area, which offers overall greater contact with crop pests. As well, these tiny particles can be engineered to better withstand degradation in the environment, offering longer-lasting protection than conventional pesticides.

Because many pesticides have been linked to birth defects, nerve damage, and cancer, scientists are pretty damn jazzed about the idea of using less of them.

But wait! Before we all lose our heads over the extreme tinification of agricultural chemicals — scientists still believe there could be a dark side to spraying our food and land with untested substances unknown to nature and immune to the usual kinds of breakdown (whaaa?! no way!).

So researchers across the world are slipping into lab coats and digging in. One project, led by Oregon State researcher Stacey Harper, is currently looking into how the compounds interact with their environment in “nano-sized ecosystems.” The research is still in its beginning stages, but the findings are slated to be published by the end of the year.

There is an obstacle and, surprise, it’s money. Scientists need more — more even than the $3.7 billion the the U.S. has invested through its National Nanotechnology Initiative to date — to assess fully the possible risks and rewards of nanotechnology.

Meanwhile, we giants here in the macro-world will continue enjoy the benefits of nanotechnology in our sunscreen, clean water, and scrumptious caramelly treats — even if invisible to us. As long as they don’t start manipulating magnets …



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October 5, 2012



Image Caption: A large natural population of evening primrose (yellow), which is a common plant in eastern North America. Agrawal’s team set up 16 identical plots. During each growing season for five years, eight of the plots were treated biweekly with an insecticide; the other eight were controls. Credit: Anurag Agrawal
 Economists know that the consumer’s taste drives variety and innovation in almost every field of industry. It is the same in the natural world. An international team of researchers has determined that just as consumers’ diverse food preferences give rise to varied menu offerings, the preferences of plant-eating insects’ play a role in maintaining and shaping the genetic variation of their host plants in a geographic area.

The new study, which will appear in the journal Science, involves aphids and the small research plant Arabidopsis thaliana, commonly known as wall cress. The findings provide the first measurable evidence that the process of natural selection and genetic diversity is driven by the predator-prey relationship between insects and plants. The pressures that natural enemies exert on plants forces them to create diverse natural defenses in order to avoid being eaten. The study also found that plants were quick to abandon those defense mechanisms when pests disappeared, confirming the high costs of these defenses.

“Our data demonstrate that there is a link between the abundance of two types of aphids and the continental distribution of Arabidopsis plants that are genetically different in terms of the biochemicals they produce to defend against insect feeding,” said UC Davis botanist Dan Kliebenstein.

Kliebenstein and his colleagues are examining the naturally occurring chemicals that the plant uses to ward off potential predators. They hope to better understand the role of these biochemicals in the environment and to explore their potential for improving human nutrition and fighting cancer.


Genetic change and variation are crucial to allowing a plant and animal species to survive changing environmental conditions such as new diseases or pests.

The team has documented that nonbiological changes, such as soil and climate variation, can exert pressures that cause genetic changes within a plant species. Prior to this study, there was little direct evidence that biological forces like feeding insects or species competition could lead to genetic variation within a single species across a large geographic area.

The scientists mapped the distribution of six different chemical profiles within Arabidopsis thaliana plants across Europe. Each chemical profile is controlled by variations in three genes. When they mapped out the geographic distribution of these genes in Arabidopsis plants, they noticed a change in the function of one of the key genes across different geographic regions. The gene that they identified changed in plants as they were tracked from southwest to northwest.

The theory that the researchers created to explain this is that two aphid species — Brevicoryne brassicae and Lipaphis erysimi (cabbage and mustard aphids, respectively) — are most likely the cause of the geographic variation. Both aphid species are abundant in the regions and they feed heavily on Arabidopsis and other related plants.

The team examined data on fluctuations in aphid populations in Europe that was collected for nearly 50 years by British researchers. What they found was that the distribution of the two aphid species closely mirrored the geographic distribution of the different variations of Arabidosis plants. One aphid preferred the northeastern chemical type, while the other preferred the southwestern chemical type.

“There is natural variation in chemical defenses which is under genetic control,” explained ecologist Tobias Züst from the University of Zurich. “And this variation is maintained by geographic variation in the composition of aphid communities.”

“Genetic variation is the raw material for evolution, so the maintenance of genetic diversity is essential if populations are to respond to future environmental changes such as climate change or environmental degradation”.

Next, the team attempted to determine whether the similarity between the distribution patterns of the plants and the two aphid species was more than a coincidence. To do this, they set up an experiment that allowed them to observe what would happen when the different aphid types fed on five generations of experimentally raised Arabidopsis thaliana plants.

The team confirmed that the plants were genetically adapting to the aphids. Each successive plant generation showed less damage from the insects’ feeding. The genetic changes that each generation of plant underwent were specific to the type of aphid that was feeding on them. Moreover, the laboratory plants evolved in a way that mirrored the geographic distribution of the two aphids and the types of defense chemicals used by Thaliana plants in the wild.

The team found growth speed made a difference as well. The faster-growing Arabidosis plant types fared better, while the slowest-growing plant types actually went extinct in the experiment.

“These data make it clear that even functionally similar plant-eating pests can affect the biochemical and genetic makeup of plant populations, playing a major role in shaping and refining the plant defenses in a natural community,” Kliebenstein said.

In control populations with no aphid feeding, successful genotypes from aphid populations were lost. This occurred because defense mechanisms are costly to the plant species.

“Genetic diversity was only maintained across the different treatments; within each treatment much of the diversity was lost. In the control populations, this meant the loss of defended genotypes, as here investment in costly defenses brings no benefit to the plant,” explained fellow researcher Lindsey Turnbull of the University of Zurich.

Commerical research in this field could eventually lead to the development of custom seeds that are resistant to specific local pest communities, thus limiting the need for pesticides.


A similar study also published in Science was conducted by the University of Toronto Mississauga (UTM) in collaboration with Cornell University, University of Montana and University of Turku in Finland. Researchers in this study found that the effect of insects on plant evolution can happen more quickly than was previously assumed, sometimes even over a single generation.

“Scientists have long hypothesized that the interaction between plants and insects has led to much of the diversity we see among plants, including crops, but until now we had limited direct experimental evidence,” says Marc Johnson, Assistant Professor in the UTM Department of Biology.

“This research fills a fundamental gap in our understanding of how natural selection by insects causes evolutionary changes in plants as they adapt, and demonstrates how rapidly these changes can happen in nature.”

The team planted evening primrose, a typically self-fertilizing plant that produces genetically identical offspring. The primroses were planted in two different plots, each containing 60 plants of 18 different genotypes.

One plot was kept free of predatory insects using the regular biweekly application of insecticide throughout the entire study period, while the other plot was left free to natural levels of insects. The plots had no other interference for five years. Each year of the study, the team counted the number and types of plants colonizing the plots and analyzed the changing frequencies of the different evening primrose genotypes and the traits associated with those genotypes.

Anurag Agrawal, professor of ecology and evolutionary biology at Cornell University, explained: “We demonstrated that when you take moths out of the environment, certain varieties of evening primrose were particularly successful. These successful varieties have genes that produce less defenses against moths.”

The study states that evolution, expressed as a change in genotype frequency over time, was observed in all plots after only a single generation. In response to insect attack or lack thereof, plant populations began to diverge significantly in as few as three to four generations. In the untreated plots, there were increases in the frequencies of genotypes associated with higher levels of toxic chemicals in the fruits, making them unpalatable to seed predator moths. Plants that flowered later in the year also increased in number since they were able to avoid most insect predators.

The findings show that evolution might be an important mechanism for changing whole ecosystems and that these changes can occur quite rapidly.

“As these plant populations evolve, their traits change and influence their interactions with insects and other plant species, which in turn may evolve adaptations to cope with those changes,” says Johnson. “The abundance and competitiveness of the plant populations is changing. Evolution can change the ecology and the function of organisms and entire ecosystems.”


The researchers also observed ecological changes that involved other plant and animal species in the plots when insects were removed. Competitor plants like dandelions colonized both sets of plots; however, they were more abundant in the plot without insects, reducing the number of evening primroses in that plot. According to the study, these changes were the result of the suppression of a moth caterpillar that prefers to feed on dandelions.

“What this research shows is that changes in these plant populations were not the result of genetic drift, but directly due to natural selection by insects on plants,” says Johnson. “It also demonstrates how rapidly evolutionary change can occur — not over millennia, but over years, and all around us.”

“This experimental demonstration of how rapid evolution can shape ecological interactions supports the idea that we need to understand feedbacks between evolutionary and ecological processes in order to be able to predict how communities and ecosystems will respond to change,” said Alan Tessier, a program director in the National Science Foundation´s (NSF) Directorate for Biological Sciences.

“One of the things farmers are trying to do is breed agricultural crops to be more resistant to pests,” said Agrawal. “Our study indicates that various genetic tradeoffs may make it difficult or impossible to maintain certain desired traits in plants that are bred for pest resistance.”

Primrose oil, for example, has been used medicinally for hundreds of years and the plant is beginning to gain popularity as an herbal remedy.  This research could be useful to the herbal and pharmaceutical industries.

Most previous real-time experiments on evolution have been conducted with bacteria in test tubes, not in nature as this study was. The team intends to keep the experiment running as a long-term living laboratory.

Copyright 2012 redOrbit.com

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High country news

NYT2008111213243014CTo save whitebark pines, apply slippery jack.

Ben Goldfarb Dec. 22, 2014

When most Westerners venture into the woods in search of fungus, they’re looking for dinner. When Cathy Cripps goes mushroom hunting, she’s trying to save a tree.

The tree in question is the whitebark pine, an iconic species that’s been devastated throughout the Northern Rockies by mountain pine beetles and a fungal disease called blister rust. We’re accustomed to thinking of fungi as a danger to biodiversity: In addition to pines, witness bats and frogs, imperiled by white-nose syndrome and chytrid, respectively. But Cripps, a mycologist at Montana State University, is captivated by the opposite story — a certain fungus may yet be what whitebark pine needs to survive.

That notion emerged from years of fieldwork in whitebark pine forests throughout the Greater Yellowstone Ecosystem. There, Cripps noticed that the soil was rife with a particular fungal species: Suillus sibericus, aka Siberian slippery jack. Suillus sibericus is a mycorrhizal fungus, meaning that it forms close symbiotic relationships with the roots of plants. The fungus draws sugar from roots, and in turn pipes nutrients back to its host tree through an underground network of fine filaments. “Each root tip gets surrounded by the fungus, just like a little sock,” Cripps says.

siberian slippery jackCripps wondered if mycorrhizal fungi could change the survival odds for whitebark pine seedlings grown in nurseries and planted for restoration. Cultivating whitebarks is an arduous process — among other complications, the seeds have to be exposed to elaborate temperature cycles in order to germinate — and not always successful. One graduate student who surveyed more than 100,000 whitebark seedlings planted in the region found that just 42 percent lived.

That low success rate is partly due to the fact that whitebark seedlings are often outcompeted by rival trees, like spruce and fir. Slippery jack offered a solution: While many other mycorrhizal fungi are “promiscuous” — they partner with more than one tree species — S. sibericus almost exclusively cohabitates with whitebark and its relatives. “We figured sibericus would give whitebark pine an advantage, without helping the tree species that are competitive with it,” Cripps says.

That’s when the hunt began. Cripps and a graduate student named Erin Lonergan foraged for slippery jack’s lemon curd-colored mushrooms in the mountains around Yellowstone and Canada’s Waterton Lakes National Park; back at MSU, they used a coffee grinder to mill the underside of the mushrooms, where spores reside, into a powder. Finally, Cripps diluted the powder with water and employed an inoculation gun — the kind you’d use to vaccinate cattle — to implant her spore concoction into the soil around whitebark seedlings growing in the Glacier National Park nursery.

In September 2010, volunteers planted about a thousand seedlings from the Glacier nursery at test sites across the border in Waterton. This summer, Cripps and Lonergan reported that, after three years, the fungal inoculation had enhanced survival by 11 percent. “Given how difficult it is to grow seedlings, even a small increase in survival is very important,” Cripps says.

Parks Canada agrees with her: They’ll be using slippery jack on future whitebark plantings in Waterton, Banff and Jasper National Parks. (Nurseries in the U.S. haven’t yet committed to the technique, but they’re interested.) Cripps still isn’t positive how slippery jack benefits pines, though she suspects it aids the tree by helping it take up nitrogen. Just as scientists are still coming to understand how certain trees die, they have a ways to go in figuring out why others live.

But for all the concern about whitebark survival, Cripps is equally worried about the other side of the symbiotic coin. “If you have a whitebark pine ghost forest where all the trees are just skeletons,” she wonders, “how long can these specific fungi persist in the soil?”

Ben Goldfarb is a Seattle-based correspondent for High Country News.

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Oct 02, 2014

Herbivores (species that eat plants; e.g. caterpillars) consume more non-native (introduced from other places) oak leaf material in areas with diverse native plant communities than in less diverse communities. Why diverse plant communities tend to resist invasion by non-native plants, remains uncertain. Researchers from the Illinois Natural History Survey and the Morton Arboretum have been examining the potential role of herbivores on the invasion of non-native plant species in diverse plant communities.

The researchers examined herbivore damage on leaves of non-native oak trees in arboreta across the United States. They found that non-native oaks in regions with high oak species diversity showed more leaf damage than those in regions with low diversity.

Ian S. Pearse, lead author on the study in the current issue of the Royal Society journal Proceedings of the Royal Society B, says that, “competition for resources has often been thought to limit invasions in diverse plant communities, but herbivory could also limit these invasions.”

While native oaks still suffered more leaf damage than non-native oaks overall, in the absence of native oaks non-native oaks showed even less leaf damage. Pearse conjectures, “Diverse plant communities are more likely to contain herbivores that are able to consume a non-native species, which may help to explain why diverse communities are able to resist invaders while others are easily dominated.”

As the introduction of non-native species increases, protection of intact plant communities and their associated herbivores may become critical to guarding against the non-native species invaders.

Explore further: Plant biodiversity under threat from general viruses
More information: Proc. R. Soc. B 7 November 2014 vol. 281 no. 1794 20141841. Published 17 September 2014. DOI: 10.1098/rspb.2014.1841
Journal reference: Proceedings of the Royal Society B
Read more at: http://phys.org/news/2014-10-herbivores-important-role-habitats-invasive.html#jCp


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