They are tiny signalling molecules that play important roles in many processes in living organisms. Researchers have developed a biosensor method for phosphatidic acid, an important messenger substance in plants.
Passion fruit woodiness caused by cowpea aphid-borne mosaic virus (CABMV), the disease that most affects passion fruit (Passiflora edulis) grown in Brazil, can be combated with a relatively simple technique.
A study published in the journal Plant Pathology shows that systematic eradication of plants with symptoms of the disease preserves the crop as a whole and keeps plants producing for at least 25 months.
The technique currently used to combat CABMV entails renewing the entire orchard every year. This is, of course, a costly procedure. According to the authors of the study, economic factors are critical for this crop, which is mostly grown by small producers.
CABMV occurs in all states of Brazil and impairs plant development. Passion fruit woodiness disease causes leaf mosaic, blisters, deformation and reduced fruit size, making the produce unmarketable. Vines are typically eliminated only when the disease is detected in the early stages of their life cycle. The researchers propose systematic roguing – removal of weak, diseased or abnormal plants – throughout the life of the crop.
The study was funded by FAPESP and CAPES, the Brazilian Ministry of Education’s Coordination for the Improvement of Higher Education Personnel. It was conducted by Brazilian researchers affiliated with the University of São Paulo’s Luiz de Queiroz College of Agriculture (ESALQ-USP), the Federal University of São Carlos (UFSCar) at Araras, the University of Southwest Bahia (UESB), and the Semiarid Agriculture Unit of the Brazilian Agricultural Research Corporation (EMBRAPA), as well as colleagues at Argentina’s National Agricultural Technology Institute (INTA).
“Roguing is a technique that has been used to combat papaya disease in Espírito Santo state since the 1980s. After several experiments, it was found to be the best way to control papaya ringspot virus type P [PRSV-P],” said Jorge Alberto Marques Rezende, Full Professor at ESALQ-USP and principal investigator for the study, which began in 2010.
CABMV is transmitted by aphid saliva and spreads throughout an orchard in a few months. The aphid species in question do not colonize the plants but merely visit them, and insecticide is not effective for control purposes.
“Insecticide affects their nervous system but takes hours to kill them. Meanwhile, they’re stimulated to feed on more plants, spreading the virus farther, so insecticide helps propagate the disease instead of controlling it,” said David Marques de Almeida Spadotti, first author of the article. The research was part of Spadotti’s postdoctoral fellowship at ESALQ-USP.
In previous experiments, the use of transgenic passion fruit plants and inoculation with attenuated variants of CABMV as a kind of vaccine also failed to control the disease. In this new study, an experimental orchard was planted in three areas belonging to ESALQ-USP in Piracicaba, São Paulo state, and two areas in Vitória da Conquista, southwestern Bahia. The experiments took place between 2013 and 2018. Approximately 100 healthy seedlings were planted in two areas of each city using trellises or T-shaped arbors connected by wires.
The vines were trained on the trellises and arbors for support but also to separate them so that the disease could easily be observed. Any buds with symptoms were identified and removed in weekly inspections.
In two other areas distant from the others, the same number of vines were planted using trellises and allowed to interlace without roguing, as in commercial plantations. The results of the two strategies were then compared.
In the absence of roguing, the virus spread throughout the crop in 120 days. In the areas submitted to systematic roguing, 8% of the vines were infected and removed after 180 days. In Piracicaba, only 16% had to be removed after 25 months, and the plants remained productive throughout this period.
The presence of CABMV in all infected or preventively removed vines was confirmed by PTA-ELISA serological testing.
“The symptoms appear eight days after inoculation of the virus on average. Roguing enables the grower to identify diseased plants visually and base control on visual inspection. Inspection should ideally be carried out at least once a week”
Spadotti said.
According to the researchers, the next step in the study entails larger pilot plantings of 1,000-2,000 passion fruit vines. In addition to eradicating diseased plants, they plan to replace them with healthy plants. The idea is to maintain the orchard for three to four years and compare it with another orchard maintained in the conventional manner, in which all plants are replaced every year.
“Because passion fruit is semiperennial, this longer production period is more advantageous from an economic standpoint than complete annual substitution,” said Rezende, principal investigator for the Thematic Project “Begomovirus and Crinivirus in Solanaceae”, which also relates to viruses in food crops.
The researchers stress, however, that if the strategy is to succeed, it should be implemented by all passion fruit growers in any given region. In addition to other plantations, the virus can spread from old or abandoned orchards, which should be eliminated.
CABMV-susceptible wild species of passion fruit in forests near plantations may also spread the disease. One of the experimental areas in Vitória da Conquista failed for this reason. When the wild plants were eliminated, the incidence of CABMV was considerably reduced.
According to IBGE, the national statistics and census bureau, Brazil is the world’s leading grower of passion fruit, with more than 550,000 metric tons produced in 2017.
Read the paper: Plant Pathology
Article source: Agência FAPESP
Author: André Julião
Image: Jorge Rezende
Plants face a dilemma in dry conditions: they have to seal themselves off to prevent losing too much water but this also limits their uptake of carbon dioxide. A sensory network assures that the plant strikes the right balance.
When water is scarce, plants can close their pores to prevent losing too much water. This allows them to survive even longer periods of drought, but with the majority of pores closed, carbon dioxide uptake is also limited, which impairs photosynthetic performance and thus plant growth and yield.
Plant accomplish a balancing act – navigating between drying out and starving in dry conditions – through an elaborate network of sensors. An international team of plant scientists led by Rainer Hedrich, a biophysicist from Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany, has now pinpointed these sensors. The results have been published in the journal Nature Plants.
When light is abundant, plants open the pores in their leaves to take in carbon dioxide (CO2) which they subsequently convert to carbohydrates in a process called photosynthesis. At the same time, a hundred times more water escapes through the microvalves than carbon dioxide flows in.
This is not a problem when there is enough water available, but when soils are parched in the middle of summer, the plant needs to switch to eco-mode to save water. Then plants will only open their pores to perform photosynthesis for as long as necessary to barely survive. Opening and closing the pores is accomplished through specialised guard cells that surround each pore in pairs. The units comprised of pores and guard cells are called stomata.
The guard cells must be able to measure the photosynthesis and the water supply to respond appropriately to changing environmental conditions. For this purpose, they have a receptor to measure the CO2 concentration inside the leaf. When the CO2 value rises sharply, this is a sign that the photosynthesis is not running ideally. Then the pores are closed to prevent unnecessary evaporation. Once the CO2 concentration has fallen again, the pores reopen.
The water supply is measured through a hormone. When water is scarce, plants produce abscisic acid (ABA), a key stress hormone, and set their CO2 control cycle to water saving mode. This is accomplished through guard cells which are fitted with ABA receptors. When the hormone concentration in the leaf increases, the pores close.
The JMU research team wanted to shed light on the components of the guard cell control cycles. For this purpose, they exposed Arabidopsis species to elevated levels of CO2 or ABA. They did so over several hours to trigger reactions at the level of the genes. Afterwards, the stomata were isolated from the leaves to analyse the respective gene expression profiles of the guard cells using bioinformatics techniques. For this task, the team took Tobias Müller and Marcus Dietrich on board, two bioinformatics experts at the University of Würzburg.
The two experts found out that the gene expression patterns differed significantly at high CO2 or ABA concentrations. Moreover, they noticed that excessive CO2 also caused the expression of some ABA genes to change. These findings led the researchers to take a closer look at the ABA signalling pathway. They were particularly interested in the ABA receptors of the PYR/PYL family (pyrabactin receptor and pyrabactin-like). Arabidopsis has 14 of these receptors, six of them in the guard cells.
“Why does a guard cell need as many as six receptors for a single hormone? To answer this question, we teamed up with Professor Pedro Luis Rodriguez from the University of Madrid, who is an expert in ABA receptors,” says Hedrich. Rodriguez’s team generated Arabidopsis mutants in which they could study the ABA receptors individually.
“This enabled us to assign each of the six ABA receptors a task in the network and identify the individual receptors which are responsible for the ABA- and CO2-induced closing of the stomata,” Peter Ache, a colleague of Hedrich‘s, explains.
“We conclude from the findings that the guard cells offset the current photosynthetic carbon fixation performance with the status of the water balance using ABA as the currency,” Hedrich explains. “When the water supply is good, our results indicate that the ABA receptors evaluate the basic hormonal balance as quasi ‘stress-free’ and keep the stomata open for CO2 supply. When water is scarce, the drought stress receptors recognise the elevated ABA level and make the guard cells close the stomata to prevent the plant from drying out.”
Next, the JMU researchers aim to study the special characteristics of the ABA and CO2 relevant receptors as well as their signalling pathways and components.
Read the paper: Nature Plants
Article source: UNIVERSITY OF WÜRZBURG
Image: Rainer Hedrich & Peter Ache / Universität Würzburg
A new species of gigantic tumbleweed once predicted to go extinct is not only here to stay — it’s likely to expand its territory.
Hidden underground networks of plant roots snake through the earth foraging for nutrients and water, similar to a worm searching for food. Yet, the genetic and molecular mechanisms that govern which parts of the soil roots explore remain largely unknown. Now, Salk Institute researchers have discovered a gene that determines whether roots grow deep or shallow in the soil.
In addition, the findings, published in Cell, will also allow researchers to develop plants that can help combat climate change as part of Salk’s Harnessing Plants Initiative. The initiative aims to grow plants with more robust and deeper roots that can store increased amounts of carbon underground for longer to reduce CO2 in the atmosphere. The Salk initiative will receive more than $35 million from over 10 individuals and organizations through The Audacious Project to further this effort.
“We are incredibly excited about this first discovery on the road to realizing the goals of the Harnessing Plants Initiative,” says Associate Professor Wolfgang Busch, senior author on the paper and a member of Salk’s Plant Molecular and Cellular Biology Laboratory as well as its Integrative Biology Laboratory. “Reducing atmospheric CO2 levels is one of the great challenges of our time, and it is personally very meaningful to me to be working toward a solution.”
In the new work, the researchers used the model plant thale cress (Arabidopsis thaliana) to identify genes and their variants that regulate the way auxin, a hormone that is a key factor in controlling the root system architecture, works. Though auxin was known to influence almost all aspects of plant growth, it was not known which factors determined how it specifically affects root system architecture.
“In order to better view the root growth, I developed and optimized a novel method for studying plant root systems in soil,” says first author Takehiko Ogura, a postdoctoral fellow in the Busch lab. “The roots of A. thaliana are incredibly small so they are not easily visible, but by slicing the plant in half we could better observe and measure the root distributions in the soil.”
The team found that one gene, called EXOCYST70A3, directly regulates root system architecture by controlling the auxin pathway without disrupting other pathways. EXOCYST70A3 does this by affecting the distribution of PIN4, a protein known to influence auxin transport. When the researchers altered the EXOCYST70A3 gene, they found that the orientation of the root system shifted and more roots grew deeper into the soil.
“Biological systems are incredibly complex, so it can be difficult to connect plants’ molecular mechanisms to an environmental response,” says Ogura. “By linking how this gene influences root behavior, we have revealed an important step in how plants adapt to changing environments through the auxin pathway.”
In addition to enabling the team to develop plants that can grow deeper root systems to ultimately store more carbon, this discovery could help scientists understand how plants address seasonal variance in rainfall and how to help plants adapt to changing climates.
“We hope to use this knowledge of the auxin pathway as a way to uncover more components that are related to these genes and their effect on root system architecture,” adds Busch. “This will help us create better, more adaptable crop plants, such as soybean and corn, that farmers can grow to produce more food for a growing world population.”
Other authors included Santosh B. Satbhai of Salk along with Christian Goeschl, Daniele Filiault, Madalina Mirea, Radka Slovak and Bonnie Wolhrab of the Gregor Mendel Institute in Austria.
About the Harnessing Plants Initiative:
Climate change poses an immediate threat to our future. Rising temperatures from excess carbon dioxide in the atmosphere has led to increasingly extreme and dangerous weather patterns that threaten animals and plants alike. The Salk Institute’s Harnessing Plants Initiative (HPI) is an innovative, scalable and bold approach to fight climate change by optimizing a plant’s natural ability to capture and store carbon and adapt to diverse climate conditions. This approach can help draw down and store more carbon and that—combined with other global efforts—will mitigate the disastrous effects of climate change while providing more food, fuel and fiber for a growing population.
Read the paper: Cell
Article source: Salk Institute
Image: Salk Institute
Citrus fruits, coffee and avocados: The food on our tables has become more diverse in recent decades. However, global agriculture does not reflect this trend. Monocultures are increasing worldwide, taking up more land than ever. At the same time, many of the crops being grown rely on pollination by insects and other animals. This puts food security at increased risk, as a team of researchers writes in the journal “Global Change Biology“. For the study, the scientists examined global developments in agriculture over the past 50 years.
The researchers analysed data from the United Nations’ Food and Agriculture Organization (FAO) on the cultivation of field crops between 1961 and 2016. Their evaluation has shown that not only is more and more land being used for agriculture worldwide, the diversity of the crops being grown has declined. Meanwhile, 16 of the 20 fastest growing crops require pollination by insects or other animals. “Just a few months ago, the World Biodiversity Council IPBES revealed to the world that up to one million animal and plant species are being threatened with extinction, including many pollinators,” says Professor Robert Paxton, a biologist at MLU and one of the authors of the new study. This particularly affects bees: honeybees are increasingly under threat by pathogens and pesticides, and populations of wild bees have been on the decline around the world for decades.
Fewer pollinators could mean that yields are much lower or even that harvests fail completely. However, risks are not spread equally across the world. The researchers used the FAO data to create a map showing the geographical risk of crop failure. “Emerging and developing countries in South America, Africa and Asia are most affected,” says Professor Marcelo Aizen of the National Council for Scientific and Technological Research CONICET in Argentina, who led the study. This is not surprising, he says, since it is precisely in these regions where vast monocultures are grown for the global market. Soy is produced in many South American countries and then exported to Europe as cattle feed. “Soy production has risen by around 30 percent per decade globally. This is problematic because numerous natural and semi-natural habitats, including tropical and subtropical forests and meadows, have been destroyed for soy fields,” explains Aizen.
According to the authors, current developments have little to do with sustainable agriculture, which focuses on the food security of a growing world population. And, although poorer regions of the world are at the greatest risk, the consequences of crop failure would be felt worldwide: “The affected regions primarily produce crops for the rich industrial nations. If, for example, the avocado harvest in South America fails, people in Germany and other industrial nations may no longer be able to buy them,” concludes Robert Paxton, who is also a member of the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig.
The researchers advocate for a trend reversal: Care should be taken to diversify agriculture worldwide and make it more ecological. This means, for example, that farms in particularly susceptible countries should grow a diversity of crops. In addition, farmers all over the world would need to make the areas under cultivation more natural, for example by planting strips of flowers or hedgerows next to their fields and by providing nesting habitats on field margins. This would ensure that there are adequate habitats for insects, which are essential for sustainable and productive farming.
Read the paper: Global Change Biology
Article source: Martin-Luther-Universität Halle-Wittenberg
Image: Martin Husemann
A team of Clemson University scientists has achieved a breakthrough in the genetics of senescence in cereal crops with the potential to dramatically impact the future of food security in the era of climate change.
The collaborative research, which explores the genetic architecture of the little understood process of senescence in maize (a.k.a. corn) and other cereal crops, was published in The Plant Cell, one of the top peer-reviewed scientific journals of plant sciences. Rajan Sekhon, a plant geneticist and an assistant professor in the College of Science’s department of genetics and biochemistry, is the lead and corresponding author of the paper titled “Integrated Genome-Scale Analysis Identifies Novel Genes and Networks Underlying Senescence in Maize.”
“Senescence means ‘death of a cell or an organ in the hands of the very organisms it is a part of,’ ” Sekhon said. “It happens pretty much everywhere, even in animals. We kill the cells we don’t need. When the weather changes in fall, we have those nice fall colors in trees. At the onset of fall, when the plants realize that they cannot sustain the leaves, they kill their leaves. It is all about the economy of energy.”
As a result, the leaves die off after their show of color. The energy scavenged from the leaves is stored in the trunk or roots of the plant and used to quickly reproduce leaves next spring. This makes perfect sense for trees. But the story is quite different for some other edible plants, specifically cereal crops like maize, rice and wheat.
“These crops are tended very carefully and supplied excess nutrients in the form of fertilizers by the farmers,” Sekhon said. “Instead of dying prematurely, the leaves can keep on making food via photosynthesis. Understanding the triggers for senescence in crops like maize means scientists can alter the plant in a way that can benefit a hungry world.”
Sekhon, whose research career spans molecular genetics, genomics, epigenetics and plant breeding, established his lab in 2014 as an assistant professor. He has played a key role in the development of a “gene atlas” widely used by the maize research community. He has published several papers in top peer-reviewed journals investigating the regulation of complex plant traits.
“If we can slow senescence down, this can allow the plant to stay green – or not senesce – for a longer period of time,” Sekhon said. “Plant breeders have been selecting for plants that senesce late without fully understanding how senescence works at the molecular level.”
These plants, called “stay-green,” live up to their name. They stay green longer, produce greater yields and are more resilient in the face of environmental factors that stress plants, including drought and heat.
But even with the existence of stay-green plants, there has been little understanding about the molecular, physiological and biochemical underpinnings of senescence. Senescence is a complex trait affected by several internal and external factors and regulated by a number of genes working together. Therefore, off-the-shelf genetic approaches are not effective in fully unraveling this enigmatic process. The breakthrough by Sekhon and his colleagues was the result of a systems genetics approach.
Sekhon and the other researchers studied natural genetic variation for the stay-green trait in maize. The process involved growing 400 different maize types, each genetically distinct from each other based on the DNA fingerprint (i.e., genotype), and then measuring their senescence (i.e., phenotype). The team then associated the “genotype” of each inbred line with its “phenotype” to identify 64 candidate genes that could be orchestrating senescence.
“The other part of the experiment was to take a stay-green plant and a non-stay-green plant and look at the expression of about 40,000 genes during senescence,” Sekhon said. “Our researchers looked at samples every few days and asked which genes were gaining expression during the particular time period. This identified over 600 genes that appear to determine whether a plant will be stay-green or not.
“One of the big issues with each of these approaches is the occurrence of false positives, which means some of the detected genes are flukes, and instances of false negatives, which means that we miss out on some of the causal genes.”
Therefore, Sekhon and his colleagues had to painstakingly combine the results from the two large experiments using a “steams genetics” approach to identify some high-confidence target genes that can be further tested to confirm their role in senescence. They combined datasets to narrow the field to 14 candidate genes and, ultimately, examined two genes in detail.
“One of the most remarkable discoveries was that sugars appear to dictate senescence,” Sekhon said. “When the sugars are not moved away from the leaves where these are being made via photosynthesis, these sugar molecules start sending signals to initiate senescence.”
However, not all forms of sugar found in the plants are capable of signaling. One of the genes that Sekhon and colleagues discovered in the study appears to break complex sugars in the leaf cells into smaller sugar molecules – six-carbon sugars like glucose and fructose – that are capable of relaying the senescence signals.
“This is a double whammy,” Sekhon said. “We are not only losing these extra sugars made by plants that can feed more hungry mouths. These unused sugars in the leaves start senescence and stop the sugars synthesis process all together.”
The implications are enormous for food security. The sugars made by these plants should be diverted to various plant organs that can be used for food.
“We found that the plant is carefully monitoring the filling of the seeds. That partitioning of sugar is a key factor in senescence. What we found is there is a lot of genetic variation even in the maize cultivars that are grown in the U.S.”
Some plants fill seeds and then can start filling other parts of the plant.
“At least some of the stay-green plants are able to do this by storing extra energy in the stems,” Sekhon said. “When the seed is harvested, whatever is left in the field is called stover.”
Stover can be used as animal feed or as a source of biofuels. With food and energy demand increasing, there is a growing interest in developing dual-purpose crops which provide both grain and stover. As farmland becomes scarce, plants that senesce later rise in importance because they produce more overall energy per plant.
The genes identified in this study are likely performing the same function in other cereal crops, such as rice, wheat and sorghum. Sekhon said that the next step is to examine the function of these genes using mutants and transgenics.
“The ultimate goal is to help the planet and feed the growing world. With ever-worsening climate, shrinking land and water, and increasing population, food security is the major challenge faced by mankind,” Sekhon said.
In addition to Sekhon, other contributors include Rohit Kumar, Christopher Saski, Arlyn Ackerman, William Bridges, Barry Flinn and Feng Luo of Clemson University; Timothy Beissinger of the University of Gottingen; and Matthew Breitzman, Natalia de Leon and Shawn Kaeppler of the University of Wisconsin-Madison.
Read the paper: The Plant Cell
Article source: Clemson University
Image: Clemson University/College of Science
Genetic testing developed by University of Missouri-Columbia scientists could aid in developing new and healthier diets.
Human genetic testing has evolved over the recent decades, allowing people to find their ancestors and even determine specific percentages of their heritage. Much like the advances in human genetic testing recently popularized by commercial organizations have allowed people to gain a better understanding of their ancestry, scientists are now a step closer to determining a genetic family tree for vegetables by linking biology with computer science.
“Domestication of plants — the process of adapting wild plants for human use — happened a long time ago before we knew about genetics,” said Makenzie Mabry, a doctoral student of biological sciences. “Initially in wild plants there is a big pool of genes, and domestication only uses a few of those genes. Therefore, we often miss out on other possible genes that may be better than the current ones. By identifying the ancestors of our domesticated plants, we can take the evolutionary jump and go back in time to determine the genes that weren’t initially selected in domestication — genes that could lead to more healthy or more nutritious plants or plants adapted to different climates — and add those back into our current domesticated plants.”
In the new study, a team of multi-institution scientists led by the University of Missouri challenged prior theories of the origins of three vegetables — canola, rutabaga and Siberian kale — by mapping the genetic family tree of these leafy greens.
The scientists ground up leaves from each plant, added a liquid chemical and placed the mixture in test tubes. Next, they analyzed the RNA and DNA in each plant with the help of computer science. In addition, they grew one of the plants, and independently verified the origin discovered in the test tubes.
“Using an analogy, some of our human genetic history comes from both our mom and dad, but other parts only come from our mom,” said J. Chris Pires, a professor of biological sciences in the College of Arts and Science and investigator in the Christopher S. Bond Life Sciences Center. “Here we are trying to determine the parents of these plants, and we found that it’s not the previously hypothesized mom nor dad, it’s some yet to be identified species.”
The team of scientists hopes to continue collecting data throughout the world to broaden their knowledge of this family tree to confidently identify the relatives of the parental species.
“Many people focus solely on the history of animals and people,” said Hong An, a postdoctoral fellow of biological sciences. “But it’s equally, if not more important, to also know the history of our food.”
Read the paper: Nature Communications
Article source: University of Missouri-Columbia
Image: University of Missouri-Columbia
Genes in green ash trees that may confer some resistance to attacks by the emerald ash borer express themselves only once the tree detects the invasive beetle’s feeding, according to Penn State researchers.
Knowing this, geneticists may be able to selectively breed trees to strengthen them and perhaps move the resistance response earlier to ward off the beetles’ onslaught, explained John Carlson, professor of molecular genetics.
Green ash, an ecologically and economically valuable tree species native to eastern and central North America, is under severe threat from the rapid invasion of emerald ash borer, a wood-boring beetle native to Asia. Penn State scientists and others are trying to save the species.
Prior observations in a green ash provenance trial — an experiment to see how plants adapt — planted at Penn State in 1978 by Kim Steiner, professor of forest biology and director of The Arboretum at Penn State, and colleagues in the U.S. Forest Service, show that a very small percentage of ash trees survive emerald ash borer infestations, seemingly because their tissues do not nourish and perhaps even sicken the beetles.
“Emerald ash borer probably entered the provenance trial unnoticed around 2008 and trees started showing symptoms of attack by 2012,” Carlson said. “All but eight or nine of the approximately 1,800 trees that Kim planted have subsequently been killed by the beetles.”
Ash trees succumb after adult beetles lay eggs on their bark. When the eggs hatch, the larvae bore into the bark and feed on the transportation tissues of the tree. This disrupts the movement of nutrients and water within the tree, girdling it and causing death.
“To better understand the response of green ash trees to emerald ash borer, we compared gene expression data for resistant versus susceptible green ash genotypes exposed to attack by the beetles,” said Carlson, director of Penn State’s Schatz Center for Tree Molecular Genetics. “By comparing RNA-sequence data from stems attacked by emerald ash borer to multiple tree tissues under other stresses, we could identify differences in the gene expression profiles specific to emerald ash borer resistance.”
The researchers found that the gene expression response in the inner bark of resistant trees is induced by emerald ash borer attack, rather than being always present, noted Di Wu, who conducted her doctoral dissertation in Carlson’s lab and is now a bioinformatics scientist in the Genomics Research Core Facility of the Cedars-Sinai Medical Center, Los Angeles.
To identify which of the genes activated by emerald ash borer attack are most important in resistance, the researchers are now looking for gene sequences that differentiate resistant from susceptible trees.
“The first step in this process was to construct a genetic linkage map with sequences from as many genes as possible, including those induced by emerald ash borer attack,” Wu said.
The researchers are examining a genetic map that includes more than 4,000 genes, and have established a field trial with green ash seedlings to await natural infestation of emerald ash borer and reveal which trees are resistant and which genetic loci in those trees are responsible.
The genetic seedlings are about five years old and are growing on the University Park campus on the site of Steiner’s green ash provenance trial.
“The trees now vary in height from less than a foot to more than 4 feet, and we hope that similar variation in susceptibility to emerald ash borer attack will be revealed as well,” Carlson said. “The mapping family was actually produced from a cross by the U.S. Forest Service of a resistant tree previously discovered in Ohio, not one of the remaining trees in Dr. Steiner’s study.”
Ironically, Carlson can only wait for the emerald ash borer to infest his field trial before he can continue the research using the genetic map, which was recently published in Plant Molecular Biology.
“I’m not sure how much older or larger the trees will need to be before being hit by the emerald ash borer,” he said. “My guess would be another three years of rapid growth before any of the seedlings will be large enough to be attacked.”
Also involved in the research were Jennifer Koch, U.S. Department of Agriculture Forest Service, Northern Research Station in Delaware, and Mark Coggeshall, Department of Forestry, Center for Agroforestry, University of Missouri, Columbia. Coggeshall is also with the U.S. Department of Agriculture Forest Service, Northern Research Station, Hardwood Tree Improvement and Regeneration Center in West Lafayette, Indiana.
Article source: Pennsylvania State University
Image: John Carlson/Penn State
New findings show that old-growth forests, a critical nesting habitat for threatened northern spotted owls, are less likely to experience high-severity fire than young-growth forests during wildfires. This suggests that old-growth forest could be leveraged to provide valuable fire refuges that support forest biodiversity and buffer the extreme effects of climate change on fire regimes in the Pacific Northwest.
A recent study published in the journal Ecosphere examined the impact of the Douglas Complex and Big Windy fires that burned in the Klamath-Siskiyou region of Oregon during July 2013, a drought year. The fires burned through a long-term study area for northern spotted owls. Using information on forest vegetation before and after the fires, along with known spotted owl nesting areas, researchers had an unprecedented chance to compare the impact of wildfire on critical old-growth nesting habitat.
“On federally managed lands, spotted owl nesting habitat is largely protected from timber harvest under the Northwest Forest Plan, but wildfire is still a primary threat to the old-growth forest that spotted owls rely on for nesting habitat,” said research wildlife biologist Damon Lesmeister. “The loss of spotted owl nesting habitat as a result of severe fire damage could have significant negative impacts on the remaining spotted owl populations as well as a large number of other wildlife species that rely on these old forests.”
Old-growth forests have more vegetation than younger forests. Researchers expected that this meant more fuel would be available for wildfires, increasing the susceptibility of old-growth forests to severe fire, high tree mortality, and resulting loss of critical spotted owl nesting habitat. However, the data suggested a different effect.
Lesmeister and his colleagues classified fire severity based on the percentage of trees lost in a fire, considering forest that lost less than 20% of its trees to fire subject to low-severity fire and those with more than 90% tree loss subject to high-severity fire. They found that old-growth forest was up to three times more likely to burn at low severity—a level that avoided loss of spotted owl nesting habitat and is generally considered to be part of a healthy forest ecosystem.
“Somewhat to our surprise, we found that, compared to other forest types within the burned area, old-growth forests burned on average much cooler than younger forests, which were more likely to experience high-severity fire. How this actually plays out during a mixed-severity wildfire makes sense when you consider the qualities of old-growth forest that can limit severe wildfire ignitions and burn temperatures, like shading from multilayer canopies, cooler temperatures, moist air and soil as well as larger, hardier trees.”
Because old-growth forests may be refuges of low-severity fire on a landscape that experiences moderate to high-severity fires frequently, they could be integral as biodiversity refuges in an increasingly fire-prone region. Leveraging the potential of old-growth forests to act as refuges may be an effective tool for forest managers as they deal with worsening fire seasons in the Pacific Northwest.
The study was a collaboration between researchers Damon Lesmeister and David Bell, USDA Forest Service, Pacific Northwest Research Station; Stan Sovern and Matthew Gregory, Oregon State University; Raymond Davis, USDA Forest Service, Pacific Northwest Region; and Jody Vogeler, Colorado State University.
The USDA Forest Service Pacific Northwest Research Station—headquartered in Portland, Ore.—generates and communicates scientific knowledge that helps people make informed choices about natural resources and the environment. The station has 11 laboratories and centers located in Alaska, Washington, and Oregon and about 300 employees.
Read the paper: Ecosphere
Article source: USDA Forest Service – Pacific Northwest Research Station
Image: USDA Forest Service photo by Damon Lesmeister
