Critical crops' alternative way to succeed in heat and drought

Scientists have discovered that certain plants can survive stressful, dry conditions by controlling water loss through their leaves without relying on their usual mechanism -- tiny pores known as 'stomata'.

Nonstomatal control of transpiration in maize, sorghum, and proso millet -- all C4 crops which are critical for global food security -- gives these plants an advantage in maintaining a beneficial microclimate for photosynthesis within their leaves.

This allows the plants to absorb carbon dioxide as part of the photosynthesis and growth process, despite raised temperatures and increased atmospheric demand for water without increasing the water expenditure.

Publishing their findings in PNAS, researchers from the University of Birmingham, Australian National University, Canberra, and James Cook University, Cairns, challenge traditional understanding of plant transpiration and photosynthesis under stressful and dry growing conditions -- namely that stomata alone control leaf water loss.

Co-author Dr Diego Márquez, from the University of Birmingham, commented: "This revolutionised our understanding of plant-water relations by showing that nonstomatal control of transpiration limits water loss without compromising carbon gain -- challenging what is typically accepted as an unavoidable trade-off.

"Our findings have significant implications for plant adaptation to climate change and how crops might be grown in arid environments. Understanding this mechanism could open new avenues for improving water-use efficiency in C4 crops, which are vital for global food security."

The study confirms that C4 plants maintain reduced relative humidities in the substomatal cavity, down to 80% under vapour pressure deficit (VPD) stress, reducing water loss and highlighting a critical role of nonstomatal control in water-use efficiency.

This mechanism helps plants sustain photosynthesis by reducing water loss without significantly lowering intercellular CO2 levels for photosynthesis. This is crucial for maintaining growth and ensuring that the crops thrive.

The findings also suggest that nonstomatal control mechanisms may have evolved before the divergence of C3 and C4 photosynthetic pathways, indicating a shared evolutionary trait.

"Our research reframes understanding of water-use efficiency in C4 plants and reveals that this alternative mechanism helps plants continue to grow and capture carbon dioxide, even when atmospheric water demand is high, challenging traditional assumptions about how these plants survive droughts," added Dr Márquez.

Photosynthesis is how plants use light and carbon dioxide to make sugars for growth, using an enzyme called Rubisco. Plants use the carbon dioxide that enters through open stomata to produce sugar, whilst open stomata also let water vapour out.

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Agricultural impact of flooding

I can barely hear Esther Ngumbi over the roar of greenhouse fans as she shows me around her rooftop laboratory in Morrill Hall. The benches are full of tomato plants, and the tomatoes don't look good. Half of the plants are submerged in bins of water. Their leaves are yellow and withering. Some of the dying tomatoes have flowered. I see one or two baby tomatoes on a couple of spindly plants.

This isn't the only torture inflicted on the tomatoes. Someone has tied little baggies to their stems. Inside the bags, fat green caterpillars are chowing down on the tomato leaves.

Entomology professor Ngumbi has questions -- lots of them -- and this is how she's set out to answer some of them. She is purposely flooding the tomatoes to see how they might respond to flooded conditions in farmers' fields -- a scenario that is becoming more common as a result of climate change.

"In nature, there are many stressors on plants during flooding," Ngumbi says. "Once the tomatoes get flooded, they're already weak, so most likely they will be attracting insects, which like to eat weaker plants. We're investigating how the plants deal with the combined stress of flooding and herbivory."

This explains the caterpillars. They are the larval form of Manduca sexta, the tobacco hornworm. They are feasting on one of the two heirloom tomato varieties Ngumbi is using in the experiment: Cherokee purple and striped German.

Half of the tomato plants in the greenhouse are not flooded, allowing the team to compare the stressed plants with those grown in more common conditions. But there are more investigations going on here.

"Also, within this experiment, we're looking at the microbes," Ngumbi says. "We want to understand how the microbial community changes in flooded conditions."

One of Ngumbi's key focuses is how soil microbes influence plant health and productivity. She's fascinated by mycorrhizal fungi, which form intimate associations with plant roots, offering essential elements like nitrogen to the plants in exchange for glucose supplied by the roots.

The tomato plants are all growing in soil from an Illinois farm, but half were also inoculated with mulch from a local farmer who has developed his own recipe for nurturing mycorrhizal fungi in the soil. Ngumbi wants to see if this inoculation makes any difference to the plants' ability to defend themselves from the fat caterpillars.

To measure plant defenses, Ngumbi's team collects samples of gases emitted by the plants and screens them for volatile organic compounds, the chemicals plants use to ward off bugs that would eat them.

Two years later, Ngumbi publishes the results of these and other laboratory experiments. She found that the two tomato varieties differed in gene expression and in the volatile compounds they emitted -- before any intervention. And when flooded, both varieties of tomatoes had very different chemical emission profiles than when grown in normal conditions. Herbivory influenced the production of these volatile compounds, but not as much as flooding did.

Today, the experiments continue, and Ngumbi's interest in the effects of flooding has only intensified. In a new review published in the journal Trends in Plant Research, she spells out the many changes that occur when plants are inundated with water for days or weeks at a time.

"Flooding is different from other climate-related stressors because it deprives plants of oxygen, an essential and indispensable element and substrate for plant growth and development," Ngumbi writes. Flooding disrupts plant metabolism and energy generation. It interferes with photosynthesis. Flooding kills beneficial bacteria and promotes pathogenic microbes in the soil. It also can compromise plants' ability to defend themselves from disease and harmful insects like the tobacco hornworm.

Ngumbi also warns that increased flooding can undermine decades of research aimed at making plants more resilient to climate change. Flooding may thwart efforts to build soil quality and microbial health to make crops more resilient to stressors such as heat and drought. Flooding also may eliminate gains derived from genetic engineering or plant breeding.

With flooding intensity and frequency predicted to increase by roughly 7% for every 1° C increase in global average temperatures, Ngumbi writes, scientists must consider the impacts of floods to "protect the monumental gains made in building climate-resilient crops."

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Honey bees experience multiple health stressors out-in-the-field

It's not a single pesticide or virus stressing honey bees, and affecting their health, but exposure to a complex web of multiple interacting stressors encountered while at work pollinating crops, found new research out of York University.

Scientists have been unable to explain increasing colony mortality, even after decades of research examining the role of specific pesticides, parasitic mites, viruses or genetics. This led the research team to wonder if previous studies were missing something by focussing on one stressor at a time.

"Our study is the first to apply systems level or network analyses to honey bee stressors at a massive scale. I think this represents a paradigm shift in the field because we have been so focussed on finding the one big thing, the smoking gun," says corresponding author of the new paper York Faculty of Science Professor Amro Zayed, York Research Chair in Genomics. "But we are finding that bees are exposed to a very complicated network of stressors that change quickly over time and space. It's a level of complexity that we haven't thought about before. To me, that's the big surprise of this study."

The paper, Honey bee stressor networks are complex and dependent on crop and region, published today in Current Biology, takes a much broader look at the interplay of stressors and their effects. The study team also included researchers from the University of British Columbia, Agriculture and Agri-Food Canada, the University of Victoria, the University of Lethbridge, the University of Manitoba, l'Université Laval, the University of Guelph, and the Ontario Beekeepers' Association.

Not all stressors are the same, however. Some stressors are more influential than others -- what researchers call the social media influencers of the bee world -- having an outsized impact on the architecture of a highly complex network and their co-stressors. They also found that most of these influencer stressors are viruses and pesticides that regularly show up in combination with specific other stressors, compounding the negative effects through their interactions.

"Understanding which stressors co-occur and are likely to interact is profoundly important to unravelling how they are impacting the health and mortality of honey bee colonies," says lead author, York Postdoctoral Fellow Sarah French of the Faculty of Science.

"There have been a lot of studies about major pesticides, but in this research, we also saw a lot of minor pesticides that we don't usually think about or study. We also found a lot of viruses that beekeepers don't typically test for or manage. Seeing the influencer stressors interact with all these other stressors, whether it be mites, other pesticides or viruses, was not only interesting, but surprising."

French says the way influencer stressors co-occur with other stressors is similar to the way humans experience co-morbidities, such as when someone is diagnosed with heart disease. They are more likely to also have diabetes or high blood pressure or both, and each one impacts the other. "That's similar to the way we examine bee colonies. We look at everything that's going on in the colony and then compare or amalgamate all the colonies together to look at the broader patterns of what is happening and how everything is related. Two or multiple stressors can really synergize off each other leading to a much greater effect on bee health."

From Québec to British Columbia, honey bee colonies were given the job of pollinating some of Canada's most valuable crops -- apples, canola oil and seed, highbush and lowbush blueberry, soybean, cranberry and corn. The study covered multiple time scales, providing numerous snapshots, rather than the usual single snapshot in time. The research team found that honey bees were exposed to an average of 23 stressors at once that combined to create 307 interactions.

Honey bees are a billion dollar industry. In 2021, honey bees contributed some $7 billion in economic value by pollinating orchards, vegetables, berries and oil seeds like canola, and produced 75 to 90 million pounds of honey. Figuring which stressors would provide the most benefit if managed would go a long way toward developing the right tools to tackle them, something beekeepers are often lacking.

The research is part of the BEECSI: 'OMIC tools for assessing bee health project funded to the tune of $10 million by Genome Canada in 2018 to use genomic tools to develop a new health assessment and diagnosis platform powered by stressor-specific markers.

More research is needed to unravel how the stressors are interacting and impacting honey bee mortality and colony health going forward, says French. "It's really teasing apart which of these compounds might have that relationship and how can we build off this to study those specific relationships."

It can't come soon enough, honey bees are currently facing poor health, colony loss, parasites, pathogens and heightened stressors worldwide. Some beekeepers in this country and the United States face a loss over winter of up to 60 per cent of their colonies.

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Paper provides a clearer picture of severe hydro hazards

Over the last two decades an estimated three billion people have been affected by water-related natural disasters such as droughts and floods. Climate change is expected to increase the frequency of these hydro hazards, with some prognosticators estimating there will be upwards of $3.7 trillion in water-related damage over the next 30 years in the U.S. alone. Beyond damaging homes and infrastructure, severe wet and dry spells will also devastate crops and deplete water reservoirs.

An increasing area of interest to researchers is the frequency of compound drought and pluvial flooding (caused by quick, heavy rainfall or sustained rainfall beyond the norm), which is when both occur in succession in the same area within a year of each other.

Historically, this level of coincidence has been under-examined.

Of similar interest is when the reverse happens: extreme rainfall followed by a meteorological drought.

Meteorological drought is when dry weather patterns prevail, which can eventually trigger hydrological drought, leading to dry streams and plunging reservoir levels, such as what happened at Lake Mead in 2022.

A new study co-authored by researchers in the University of Arkansas Department of Geosciences, as well as colleagues in China, now provides a global examination of drought-pluvial volatility -- or the tendency to shift from one extreme to another (from dry to wet or wet to dry) in a short period of time.

Yichan Li, a Ph.D. candidate at the U of A, was the first of four authors on the paper, "Observational Uncertainty for Global Drought-Pluvial Volatility," published in Water Resources Research, while Linyin Cheng, an assistant professor of geosciences, was second author.

The study looks at extreme dry-to-wet and wet-to-dry transitions over the past seven decades through event coincidence analysis, a method of quantifying the number of consecutive extreme events that also considers instantaneous or lagged responses within an uncertain period between them.

The study used three widely used climate data sets to provide evidence of increased drought-pluvial volatility on time scales of less than a year.

The team also evaluated the accuracy of these data sets, finding varying strengths and weaknesses of each due to observational uncertainties in data collection.

For instance, the remoteness of a region may play a role in collecting accurate data.

Averaged out at the global scale, the team found that 15.46% of all meteorological droughts were succeeded by a pluvial the following season.

The wet-to-dry transition percentage proved remarkably similar: 15.49%. However, prominent differences exist when looking at particular regions.

Toward that end, the study provides a map demonstrating how incidents of these two phenomena are distributed globally.

Overall, the spatial pattern of extreme dry-to-wet and wet-to-dry events' coincidence rates is largely in agreement among the three data sets, though there is prominent regional variability.

For instance, in Eurasia since the mid-20th century, there is a relatively low probability for meteorological droughts transitioning to pluvials, but a higher chance for the opposite scenario, rapid shifts from wet to dry events.

A similar pattern also exists over western North America, which sees severe wet to dry transitions at a frequency greater than 17% on average.

Conversely, South Asia and Australia are more prone to immediate transitions from meteorological droughts to pluvials.

The authors noted: "Our findings indicate that differences associated with drought-pluvial volatility among the considered observations are in many regions larger than that of their single events [droughts or pluvials alone], highlighting a need of to use multiple independent observation-based data sets for more robust examinations when studying such compound extreme events."

Ultimately, the authors stress the need to use multiple independent observation-based data sets when analyzing extreme, compound dry-to-wet events.

This will provide clearer guidelines for climate-related decision making, especially water resources planning, as well as ensure better accuracy when modeling future weather events.

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Scientists engineer plant microbiome to protect crops against disease

Breakthrough could dramatically cut the use of pesticides and unlock other opportunities to bolster plant health

Scientists have engineered the microbiome of plants for the first time, boosting the prevalence of 'good' bacteria that protect the plant from disease.

The findings published in Nature Communications by researchers from the University of Southampton, China and Austria, could substantially reduce the need for environmentally destructive pesticides.

There is growing public awareness about the significance of our microbiome -- the myriad of microorganisms that live in and around our bodies, most notably in our guts.

Our gut microbiomes influence our metabolism, our likelihood of getting ill, our immune system, and even our mood.

Plants too host a huge variety of bacteria, fungi, viruses, and other microorganisms that live in their roots, stems, and leaves.

For the past decade, scientists have been intensively researching plant microbiomes to understand how they affect a plant's health and its vulnerability to disease.

"For the first time, we've been able to change the makeup of a plant's microbiome in a targeted way, boosting the numbers of beneficial bacteria that can protect the plant from other, harmful bacteria," says Dr Tomislav Cernava, co-author of the paper and Associate Professor in Plant-Microbe Interactions at the University of Southampton.

"This breakthrough could reduce reliance on pesticides, which are harmful to the environment. We've achieved this in rice crops, but the framework we've created could be applied to other plants and unlock other opportunities to improve their microbiome. For example, microbes that increase nutrient provision to crops could reduce the need for synthetic fertilisers."

The international research team discovered that one specific gene found in the lignin biosynthesis cluster of the rice plant is involved in shaping its microbiome.

Lignin is a complex polymer found in the cell walls of plants -- the biomass of some plant species consists of more than 30 per cent lignin.

First, the researchers observed that when this gene was deactivated, there was a decrease in the population of certain beneficial bacteria, confirming its importance in the makeup of the microbiome community.

The researchers then did the opposite, over-expressing the gene so it produced more of one specific type of metabolite -- a small molecule produced by the host plant during its metabolic processes.

This increased the proportion of beneficial bacteria in the plant microbiome.

When these engineered plants were exposed to Xanthomonas oryzae -- a pathogen that causes bacterial blight in rice crops, they were substantially more resistant to it than wild-type rice.

Bacterial blight is common in Asia and can lead to substantial loss of rice yields.

It's usually controlled by deploying polluting pesticides, so producing a crop with a protective microbiome could help bolster food security and help the environment.

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A mixed origin made maize successful

Maize is one of the world's most widely grown crops. It is used for both human and animal foods and holds great cultural significance, especially for indigenous peoples in the Americas. Yet despite its importance, the origins of the grain have been hotly debated for more than a century. Now new research, published Dec. 1 in Science, shows that all modern maize descends from a hybrid created just over 5000 years ago in central Mexico, thousands of years after the plant was first domesticated.

The work has implications both for improving one of the world's most important crops and for understanding how the histories of people and their crops influence each other.

"It's a new model for the origins and spread of maize, and how it became a staple across the Americas," said Jeffrey Ross-Ibarra, professor in the Department of Evolution and Ecology at the University of California, Davis and senior author on the paper.

For the last few decades, the consensus has been that maize (Zea mays) was domesticated once from a single wild grass -- called teosinte -- in the lowlands of southwest Mexico about 9,000 to 10,000 years ago.

Known as corn in the United States, maize is not only a staple of diets around the globe, but also can be processed into sweeteners,ethanol fuel and other uses.

More recently, though, it's become clear that the genome of modern maize also contains a hefty dose of DNA from a second teosinte that grows in the highlands of central Mexico.

Ross-Ibarra and collaborators in the U. S., China and Mexico analyzed the genomes of over a thousand samples of maize and wild relatives.

They found that about 20 percent of the genome of all maize worldwide comes from this second highland teosinte.

New model for spread of maize

These new findings suggest that, though maize was domesticated around 10,000 years ago, it was not until 4,000 years later, when it hybridized with highland teosinte, that maize really took off as a popular crop and food staple.

This is also supported by archaeological evidence of the increasing importance of maize around the same time.

The new crop spread rapidly through the Americas and later worldwide.

Today, about 1.2 billion metric tons is harvested each year globally.

The hunt for why highland teosinte enabled maize to become a staple is still underway, Ross-Ibarra said.

The researchers did find genes related to cob size -- perhaps representing an increased yield potential -- and flowering time, which likely helped maize, a tropical crop, to grow at higher latitudes with longer days.

Hybridization may also have brought "hybrid vigor," where a hybrid organism is more vigorous than either of its parents.

The researchers observed that genomic segments from highland teosinte contained fewer harmful mutations than did other parts of the genome.

While the initial hybridization may have been accidental, it's likely that indigenous farmers recognized and took advantage of the novel variation introduced from highland maize, Ross-Ibarra said.

Even today, he said, "If you talk to Mexican farmers, some will tell you that letting wild maize grow near the fields makes their crops stronger."

A team led by Ross-Ibarra with Professor Graham Coop at UC Davis, archaeologists at UC Santa Barbara and geneticists at Swedish University of Agricultural Sciences was recently awarded a $1.6 million grant from the National Science Foundation to study the co-evolution of humans and maize in the Americas.

They will use genetics to look at how humans and maize spread across the continent and how populations of both maize and humans grew and shrank as they interacted with each other.

"We will incorporate human genetic data, maize genetics and archaeological data in an effort to answer many of the questions raised by our new model of maize origins," Ross-Ibarra said.

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Protein root discovery seals future of climate-proof plants

Researchers have discovered a protein that seals plant roots to regulate the uptake of nutrients and water from the soil, the discovery could help develop climate proof crops that require less water and chemical fertilizers.

Researchers from the University of Nottingham identified new components of the lignin barrier in plant roots and the specific function of dirigent proteins (DPs), located in the root endodermis that control water and nutrient uptake. Their findings have been published today in Science Direct.

Plant roots function by absorbing mineral nutrients and water from the soil and also controlling their proper balance in the plant. This control is exerted by a specialised layer of root tissue called the endodermis.

The endodermis contains a barrier to the movement of solutes and water that is made of lignin, the same material present in wood. This impermeable barrier blocks the uncontrolled movement of material into the root, by forming a tight seal between cells. This seal ensures the only pathway for nutrients and water to be taken up by roots is through the cells of the endodermis. This allows full cellular control over what enters and leaves the plant via the roots.

This research has identified new components of the lignin deposition machinery that focus on the function of dirigent proteins (DPs), located in the root endodermis. These proteins act in coordination with other described root regulatory components to direct and organize the correct deposition of lignin in the endodermis allowing the plant to ensure it receives the optimum balance of nutrients from the soil.

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Natural GM crops: Grasses take evolutionary shortcut by borrowing genes from their neighbors

Grass may transfer genes from their neighbours in the same way genetically modified crops are made, a new study has revealed.

Research, led by the University of Sheffield, is the first to show the frequency at which grasses incorporate DNA from other species into their genomes through a process known as lateral gene transfer.

The stolen genetic secrets give them an evolutionary advantage by allowing them to grow faster, bigger or stronger and adapt to new environments quicker.

Understanding the rate is important to know the potential impact it can have on a plant's evolution and how it adapts to the environment.

Grasses are the most ecologically and economically important group of plants, covering 30% of the earth's terrestrial surface and producing a majority of our food.

The Sheffield team sequenced multiple genomes of a species of tropical grass and determined at different time points in its evolution how many genes were acquired -- giving a rate of accumulation.

It is now thought these transfers are likely to occur in the same way that some genetically modified crops are made.

These findings, published in the journal New Phytologist could inform future work to harness the process to improve crop productivity and make more resilient crops, and have implications on how we view and use controversial GM crops.

Dr. Luke Dunning, Research Fellow from the University of Sheffield's School of Biosciences, and senior author of the research, said: "There are many methods to make GM crops, some which require substantial human intervention and some that don't. Some of these methods that require minimal human intervention could occur naturally and facilitate the transfers we have observed in wild grasses.

"These methods work by contaminating the reproductive process with DNA from a third individual. Our current working hypothesis, and something we plan to test in the near future, is that these same methods are responsible for the gene transfers we document in wild grasses.

"This means, in the near future, controversial genetic modification could be perceived as more of a natural process.

"Currently, these 'natural' reproductive contamination methods are not as efficient in producing GM plants as those that are used routinely, but by further understanding how lateral gene transfer occurs in the wild we may be able to increase the success of this process."

Since Darwin, much of our understanding of evolution has been based on the assumption that genetic information is passed from parents to offspring -- the rule of common descent for plant and animal evolution.

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Mysterious family of microbial proteins hijack crops' cellular plumbing

Many of the bacteria that ravage crops and threaten our food supply use a common strategy to cause disease: they inject a cocktail of harmful proteins directly into the plant's cells.

For 25 years, biologist Sheng-Yang He and his senior research associate Kinya Nomura have been puzzling over this set of molecules that plant pathogens use to cause diseases in hundreds of crops worldwide ranging from rice to apple trees.

Now, thanks to a team effort between three collaborating research groups, they may finally have an answer to how these molecules make plants sick -- and a way to disarm them.

The findings appear Sept. 13 in the journal Nature.

Researchers in the He lab study key ingredients in this deadly cocktail, a family of injected proteins called AvrE/DspE, that cause diseases ranging from brown spot in beans and bacterial speck in tomatoes to fire blight in fruit trees.

Ever since their discovery in the early 1990s, this family of proteins has been of great interest to those who study plant disease. They are key weapons in the bacterial arsenal; knocking them out in a lab renders otherwise-dangerous bacteria harmless. But, despite decades of effort, many questions about how they work remain unanswered.

Researchers had identified a number of proteins in the AvrE/DspE family that suppressed the plant's immune system, or that caused dark water-soaked spots on a plant's leaves -- the first telltale signs of infection. They even knew the underlying sequence of amino acids that linked to form the proteins, like beads on a string. But they didn't know how this string of amino acids folded into a 3D shape, so they couldn't easily explain how they worked.

Part of the problem is that the proteins in this family are huge. Whereas an average bacterial protein might be 300 amino acids long; AvrE/DspE-family proteins are 2000.

Researchers have looked for other proteins with similar sequences for clues, but none with any known functions showed up.

"They're weird proteins," He said.

So they turned to a computer program released in 2021 called AlphaFold2, which uses artificial intelligence to predict what 3D shape a given string of amino acids will take.

The researchers knew that some members of this family help the bacteria evade the plant's immune system. But their first glimpse of the proteins' 3D structure suggested an additional role.

"When we first saw the model, it was nothing like what we had thought," said study co-author Pei Zhou, a professor of biochemistry at Duke whose lab contributed to the findings.

The researchers looked at AI predictions for bacterial proteins that infect crops including pears, apples, tomatoes and corn, and they all pointed to a similar 3D structure. They appeared to fold into a tiny mushroom with a cylindrical stem, like a straw.

The predicted shape matched up well with images of a bacterial protein that causes fire blight disease in fruit trees that was captured using a cryo-electron microscope. From the top down, this protein looked very much like a hollow tube.

Which got the researchers thinking: Perhaps bacteria use these proteins to punch a hole in the plant cell membrane, to "force the host for a drink" during infection, He said.

Once bacteria enter the leaves, one of the first areas they come across is a space between cells called the apoplast. Normally, plants keep this area dry to enable gas exchange for photosynthesis. But when bacteria invade, the inside of the leaf becomes waterlogged, creating a moist cozy haven for them to feed and multiply.

Further examination of the predicted 3D model for the fire blight protein revealed that, while the outside of the straw-like structure is water-resistant, its hollow inner core has a special affinity for water.

To test the water channel hypothesis, the team joined forces with Duke biology professor Ke Dong and co-first-author Felipe Andreazza, a postdoctoral associate in her lab. They added the gene readouts for the bacterial proteins AvrE and DspE to frog eggs, using the eggs as cellular factories for making the proteins. The eggs, placed in a dilute saline solution, quickly swelled and burst with too much water.

The researchers also tried to see if they could disarm these bacterial proteins by blocking their channels. Nomura focused on a class of tiny spherical nanoparticles called PAMAM dendrimers. Used for more than two decades in drug delivery, these dendrimers can be made with precise diameters in a lab.

"We were tinkering with the hypothesis that if we found the right diameter chemical, maybe we could block the pore," He said.

After testing different sized particles, they identified one they thought might be just the right size for jamming the water channel protein produced by the fire blight pathogen, Erwinia amylovora.

They took frog eggs engineered to synthesize this protein and doused them with the PAMAM nanoparticles, and water stopped flowing into the eggs. They didn't swell.

They also treated Arabidopsis plants infected with the pathogen Pseudomonas syringae, which causes bacterial speck. The channel-blocking nanoparticles prevented the bacteria from taking hold, reducing pathogen concentrations in the plants' leaves by 100-fold.

The compounds were effective against other bacterial infections too. The researchers did the same thing with pear fruits exposed to the bacteria that cause fire blight disease, and the fruits never developed symptoms -- the bacteria didn't make them sick.

"It was a long shot, but it worked," He said. "We're excited about this."

The findings could offer a new line of attack against many plant diseases, the researchers said.

Plants produce 80% of the food we eat. And yet more than 10% of global food production -- crops such as wheat, rice, maize, potato and soybean -- are lost to plant pathogens and pests each year, costing the global economy a whopping $220 billion.

The team has filed a provisional patent on the approach.

The next step, said Zhou and co-first-author Jie Cheng, a Ph.D. student in Zhou's lab, is to figure out how this protection works, by getting a more detailed look at how the channel-blocking nanoparticles and the channel proteins interact.

"If we can image those structures we can have a better understanding and come up with better designs for crop protection," Zhou said.

Read more at Science Daily

Global flash droughts expected to increase in a warming climate

The rapid development of unexpected drought, called flash drought, can severely impact agricultural and ecological systems with ripple effects that extend even further. Researchers at the University of Oklahoma are assessing how our warming climate will affect the frequency of flash droughts and the risk to croplands globally.

Jordan Christian, a postdoctoral researcher, is the lead author of the study, "Global projections of flash drought show increased risk in a warming climate," published today in Nature Communications Earth and Environment.

"In this study, projected changes in flash drought frequency and cropland risk from flash drought are quantified using global climate model simulations," Christian said. "We find that flash drought occurrence is expected to increase globally among all scenarios, with the sharpest increases seen in scenarios with higher radiative forcing and greater fossil fuel usage."

Radiative forcing describes the imbalance of radiation where more radiation enters Earth's atmosphere than leaves it. Like burning fossil fuels, these activities are among the most significant contributors to climate warming. The changing climate is expected to increase severe weather events from storms, flash flooding, flash droughts and more.

"Flash drought risk over cropland is expected to increase globally, with the largest increases projected across North America and Europe," Christian said.

"CMIP6 models projected a 1.5 times increase in the annual risk of flash droughts over croplands across North America by 2100, from the 2015 baseline of a 32% yearly risk in 2015 to 49% in 2100, while Europe is expected to have the largest increase in the most extreme emissions scenario (32% to 53%), a 1.7 times increase in annual risk," he said.

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'Devastating' fungal infections wiping out crops and threatening global food security, experts warn

Scientists have warned of the "devastating" impact that fungal disease in crops will have on global food supply unless agencies across the world come together to find new ways to combat infection.

Worldwide, growers lose between 10 and 23 per cent of their crops to fungal infection each year, despite widespread use of antifungals. An additional 10-20 per cent is lost post harvest[GS1] . In a commentary in Nature, academics predict those figures will worsen as global warming means fungal infections are steadily moving polewards[GS2] [GS3] [GS4] [VL5] , meaning more countries are likely to see a higher prevalence of fungal infections damaging harvests*. Growers have already reported wheat stem rust infections -- which normally occur in the tropics -- in Ireland and England. The experts also warn that tolerance to higher temperatures in fungi could increase the likelihood of opportunistic soil-dwelling pathogens to hop hosts, and infect animals or humans.

Professor Sarah Gurr, Chair in Food Security at the University of Exeter, co-authored the report. She said fungi had recently attracted attention through popular hit TV show The Last of Us, in which fungi take over human brains. She said: "While the storyline is science fiction, we are warning that we could see a global health catastrophe caused by the rapid global spread of fungal infections as they develop increasing resistance in a warming world. The imminent threat here is not about 'zombies,' but about global starvation."

Across the world, food security is expected to encounter unprecedented challenges as rising populations mean more demand. Across the five most important calorie crops of rice, wheat, maize (corn), soya beans and potatoes, infections cause losses which equate to enough food to provide some 600 million to 4 billion people with 2,000 calories every day for one year.

Commentary co-author Eva Stukenbrock, professor and head of the Environmental Genomics group at Christian-Albrechts University of Kiel, Germany, and fellow of the Canadian Institute for Advanced Research (CIFAR), said: "As our global population is projected to soar, humanity is facing unprecedented challenges to food production. We're already seeing massive crop losses to fungal infection, which could sustain millions of people each year. This worrying trend may only worsen as a warming world makes fungal infections more prevalent in European crops, and as they continue to develop resistance to antifungals. This will be catastrophic for developing countries and will have a major impact in the Western world, too."

The commentary highlights a "perfect storm" which is causing fungal infections to spread rapidly. Among the factors is the fact that fungi are incredibly resilient, remaining viable in soil for up to 40 years, with airborne spores that can travel between continents. Added to this, they are extremely adaptable, with "phenomenal" genetic diversity between and among species. Modern farming practices entail vast areas of genetically uniform crops, which provide the ideal feeding and breeding grounds for such a prolific and fast-evolving group of organisms. They are also well equipped to evolve beyond traditional means to control their spread. The increasingly widespread use of antifungal treatments that target a single fungal cellular process means fungi can evolve resistance to these fungicides, so that they are no longer effective. This forces farmers to use ever-higher concentrations of fungicide in a bid to control infection, which can accelerate the pace of resistance developing.

However, there is some cause for hope. In 2020, a team the University of Exeter [GS6] discovered a new chemistry which could pave the way for a new type of antifungal targets several different mechanisms, meaning it is much harder for fungi to develop resistance. The Exeter group found the antifungal to be useful against a range of fungal diseases -- Septoria tritici blotch on wheat, rice blast , corn smut[GS7] ** and against the fungus which causes Panama disease of bananas***.

Farming practices may also hold the key to change, after a study in Denmark showed promise by planting seed mixtures which carry a range of genes which are resistant to fungal infection. Technology may also prove crucial, with AI, citizen science and remote sensing tools such as drones allowing for early detection and control of outbreaks.

Overall, the authors argue that protecting the world's crops from fungal disease will require a far more unified approach, bringing together farmers, the agricultural industry, plant breeders, biologists, governments, policymakers and funders.

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Early crop plants were more easily 'tamed'

The story of how ancient wolves came to claim a place near the campfire as humanity's best friend is a familiar tale (even if scientists are still working out some of the specifics). In order to be domesticated, a wild animal must be tamable -- capable of living in close proximity to people without exhibiting dangerous aggression or debilitating fear. Taming was the necessary first step in animal domestication, and it is widely known that some animals are easier to tame than others.

But did humans also favor certain wild plants for domestication because they were more easily "tamed"? Research from Washington University in St. Louis calls for a reappraisal of the process of plant domestication, based on almost a decade of observations and experiments. The behavior of erect knotweed, a buckwheat relative, has WashU paleoethnobotanists completely reassessing our understanding of plant domestication.

"We have no equivalent term for tameness in plants," said Natalie Mueller, assistant professor of archaeology in Arts & Sciences at Washington University. "But plants are capable of responding to people. They have a developmental capacity to be tamed."

Her work with early indigenous North American crops shows that some wild plants respond quickly to clearing, fertilizing, weeding or thinning. Plants that respond in ways that make cultivation easier or more productive could be considered more easily tamed than those that cannot.

"If plants responded rapidly in ways that were beneficial to early cultivators -- for example by producing higher yields, larger seeds, seeds that were easier to sprout, or a second crop in a single growing season -- this would have encouraged humans to continue investing in the co-evolutionary relationship," she said.

This capacity to express different traits and characteristics in response to the environment is called plasticity, and not all species are equally plastic.

"Some plants respond quickly and obviously to cultivation and care," Mueller said. "I think ancient people would have noticed that they could double their yields just by thinning out dense stands of plants. This is one of the simplest and most common gardening techniques, but it has many important effects on the development of plants."

What would an early farmer do?

Mueller's study, published April 7 in PLOS ONE, focuses on work with a plant called erect knotweed, a member of the buckwheat family that was domesticated by indigenous farmers in eastern North America. The domesticated sub-species is now extinct; humans don't eat it anymore. But Mueller and others have previously uncovered caches of seeds stored in caves, charred plant remnants in ancient hearths, and even the seeds of erect knotweed in human feces, clear evidence that this species was once consumed as a staple food.

Mueller, who studies lost crops, has spent years growing erect knotweed and other crop progenitors in experimental gardens, including at Washington University's environmental field station, Tyson Research Center. She hasn't always been successful with growing the plants she collects in the wild. In that way, Mueller can relate to the early farmers who similarly experimented with plants to discover their potential.

Her efforts have often been stymied by seed dormancy, a common feature among wild plants.

Unlike seeds you buy at the garden store, the seeds of most wild plants will not germinate if you simply sprinkle some water on them. Their requirements for germination are diverse and shaped by their evolutionary history. For example, if a plant has evolved in a place with a winter, like the Midwest, its seeds may not germinate unless they experience a long cold period. This prevents them from germinating too soon in the wild -- they are waiting for spring. Domesticated plants have lost their diverse germination requirements.

The loss of germination inhibitors has presented a paradox to theorists of domestication. Many of the selective pressures that could have favored the evolution of this trait derive from planting seeds. But why would ancient people have started planting seeds if none of them germinated?

With erect knotweed, Mueller experienced a breakthrough of sorts. Based on four seasons of observations, Mueller determined that growing wild plants in the low-density conditions typical of a cultivated garden (i.e. spaced out and weeded) triggers plants to produce seeds that germinate more easily. This makes the harvests easier to plant successfully the next time around, eliminating a key barrier to further selection.

"Our results show that erect knotweed grown in low-density agroecosystems spontaneously 'act domesticated' in a single growing season, before any selection has occurred," Mueller said.

Think of it as the plant equivalent to that first wolf who, though still a wild animal, sat down with its human friend around the fire. This is a behavioral shift, rather than an evolutionary one, but it allows new evolutionary pathways to open up.

A role for plant behavior

Mueller believes there is a bias in domestication studies toward viewing this changeability, or plasticity, as noise that is getting in the way of attempts to explain evolutionary change. Instead, this paper argues that we need to understand the development and behavior of wild crop relatives in order to explain the evolutionary process of domestication.

"Because we lack the practical experience with crop progenitors that ancient people had, these effects of the environment on plant development have gone mostly unnoticed and understudied," Mueller said.

Her findings could have applications for developing new food crops: there is no reason why we have to be limited to the plants that our ancestors domesticated thousands of years ago.

Some researchers have been calling for de novo domestication -- selecting wild plants with desirable characteristics and intentionally domesticating them. It may make sense to start looking to wild plants that are easily tamed as potential crops that could be developed for the future, Mueller said.

This paper also contributes to a growing awareness that plants are responsive and communicative beings. Though this idea is cutting-edge and hotly debated in biology and ecology, it is widespread in indigenous North American philosophies and probably would have been held by the people who domesticated erect knotweed and other plants thousands of years ago.

Recent research has shown how plants warn relatives about herbivores using chemical signaling, share resources through mycorrhizal networks and even emit noises when they are injured or stressed.

Read more at Science Daily

Agriculture linked to changes in age-independent mortality in North America

The transition to agriculture from hunting and gathering in pre-colonial North America led to changes in age-independent mortality, or mortality caused by factors that are not associated with age, according to a new study by a Penn State-led research team. The team found that the intensification of crop use occurred in two phases, the first of which led to a decline in human age-independent mortality, while the second is associated with a rise in it. The study is the first to tie patterns of age-independent mortality to food production.

"This study tells the story of our shared human experience," said George Milner, distinguished professor of anthropology at Penn State and lead author. "We have several examples around the world where we see a move toward crop domestication as an independent event -- eastern North America, particularly the midcontinent, being one of them, but so too the Fertile Crescent in the Middle East. Also, there are demographic changes happening. This paper addresses the relationship between the move toward agriculture and demographic change."

The researchers examined previously published data to identify general trends in archaeobotanical samples, or the remains of plants in the archaeological record, and skeletal samples from sites across eight states stretching from Illinois to northern Alabama. They wanted to study the relationship between the domestication of crops and an index that uses skeletal data to capture the frequency of juveniles aged five to 19 years old relative to all individuals aged five or more. Anthropologists normally use the index to measure fertility rates and population growth, but the new work shows it is more responsive to age-independent mortality.

Mortality models, including those for pre-industrial societies, contain three components: juvenile mortality, which declines as children get older; adult mortality, where the probability of dying increases with advancing age; and age-independent mortality, an equal probability of dying for members of all age groups, which might occur in extreme events like food shortages, epidemics or warfare.

The researchers studied the archaeobotanical data to identify where the record showed an increase in the consumption of domesticated crops compared to foraged foods like nuts. They also examined skeletal data to identify decreases or increases in the indicator of age-independent mortality. The index focuses on individuals between five and 19 years old because in human populations that age range is characterized by low mortality relative to other age groups. Increases in mortality for this age group would indicate the occurrence of events like famines or conflict.

The researchers identified a strong correlation between crop domestication and changing age-independent mortality rates. Crop domestication happened in two stages in pre-colonial North America, with a decrease in age-independent mortality noted during the first stage of crop domestication and a rise during the second stage. The researchers reported their findings in the Proceedings of the National Academy of Sciences.

"What we've found is the index that has traditionally been interpreted as a fertility and population growth indicator is more tightly correlated to age-independent mortality, which reflects the number of deaths in the part of the age distribution where very few people die," said Milner. "This means that the pattern of first adoption of agriculture, seen elsewhere in the world and observed in eastern North America as well, coincides with lower age-independent mortality. Basically, it's good times, and that's what we see culturally."

The first stage of agricultural intensification in North America, which includes the cultivation of plants such as squash, sunflower and other native plants, occurred approximately 2,000 years ago during the Middle Woodland period up to about A.D. 500, said Milner. Indigenous societies flourished during this time. They established long-distance exchange networks, had an incredibly rich ceremonial life, and constructed big mounds and earthwork complexes.

The archaeological record shows that in the centuries just before A.D. 1000, and from that time onward, there was an increase in warfare. During this time Indigenous societies began cultivating maize and beans, and a number of new cultural changes occurred, including the initial development of powerful chiefdom societies. Age-independent mortality increased during this period, presumably due to conflict and the spread of diseases from higher numbers of individuals living near one another.

"The overall pattern seen in the demographic picture of North American pre-European contact is similar to other datasets from around the world," Milner said. "The entire story makes perfect sense in terms of agricultural productivity, demographic change and cultural developments, including change over time in conflict and sociopolitical systems."

The study links, for the first time, a worldwide pattern to age-independent mortality and agricultural developments, according to Milner.

Read more at Science Daily

How intensive agriculture turned a wild plant into a pervasive weed

New research in Science is showing how the rise of modern agriculture has turned a North American native plant, common waterhemp, into a problematic agricultural weed.

An international team led by researchers at the University of British Columbia (UBC) compared 187 waterhemp samples from modern farms and neighbouring wetlands with more than 100 historical samples dating as far back as 1820 that had been stored in museums across North America. Much like the sequencing of ancient human and neanderthal remains has resolved key mysteries about human history, studying the plant's genetic makeup over the last two centuries allowed the researchers to watch evolution in action across changing environments.

"The genetic variants that help the plant do well in modern agricultural settings have risen to high frequencies remarkably quickly since agricultural intensification in the 1960s," said first author Dr. Julia Kreiner, a postdoctoral researcher in UBC's Department of Botany.

The researchers discovered hundreds of genes across the weed's genome that aid its success on farms, with mutations in genes related to drought tolerance, rapid growth and resistance to herbicides appearing frequently. "The types of changes we're imposing in agricultural environments are so strong that they have consequences in neighbouring habitats that we'd usually think were natural," said Dr. Kreiner.

The findings could inform conservation efforts to preserve natural areas in landscapes dominated by agriculture. Reducing gene flow out of agricultural sites and choosing more isolated natural populations for protection could help limit the evolutionary influence of farms.

Common waterhemp is native to North America and was not always a problematic plant. Yet in recent years, the weed has become nearly impossible to eradicate from farms thanks to genetic adaptations including herbicide resistance.

"While waterhemp typically grows near lakes and streams, the genetic shifts that we're seeing allow the plant to survive on drier land and to grow quickly to outcompete crops," said co-author Dr. Sarah Otto, Killam University Professor at the University of British Columbia. "Waterhemp has basically evolved to become more of a weed given how strongly it's been selected to thrive alongside human agricultural activities."

Notably, five out of seven herbicide-resistant mutations found in current samples were absent from the historical samples. "Modern farms impose a strong filter determining which plant species and mutations can persist through time," said Dr. Kreiner. "Sequencing the plant's genes, herbicides stood out as one of the strongest agricultural filter determining which plants survive and which die."

Waterhemp carrying any of the seven herbicide resistant mutations have produced an average of 1.2 times as many surviving offspring per year since 1960 compared to plants that don't have the mutations.

Herbicide resistant mutations were also discovered in natural habitats, albeit at a lower frequency, which raises questions about the costs of these adaptations for plant life in non-agricultural settings. "In the absence of herbicide applications, being resistant can actually be costly to a plant, so the changes happening on the farms are impacting the fitness of the plant in the wild," said Dr. Kreiner.

Agricultural practices have also reshaped where particular genetic variants are found across the landscape. Over the last 60 years, a weedy southwestern variety has made an increasing progression eastward across North America, spreading their genes into local populations as a result of their competitive edge in agricultural contexts.

"These results highlight the enormous potential of studying historical genomes to understand plant adaptation on short timescales," says Dr. Stephen Wright, co-author and Professor in Ecology and Evolutionary Biology at the University of Toronto. "Expanding this research across scales and species will broaden our understanding of how farming and climate change are driving rapid plant evolution."

Read more at Science Daily

Thirsty wheat needed new water management strategy in ancient China

Research from Washington University in St. Louis shows that a practice of purposeful water management, or irrigation, was adopted in northern China about 4,000 years ago as part of an effort to grow new grains that had been introduced from southwest Asia.

But the story gets more complex from there. Wheat and barley arrived on the scene at about the same time, but early farmers only used water management techniques for wheat. The results, reported Nov. 9 in the journal Antiquity, raise awareness that the dispersal of domesticated crops and the knowledge of best using them can be traced independently across time and space.

"Pioneering farmers who cultivated wheat in this region managed water to meet the higher demand of this newly introduced grain," said Xinyi Liu, an associate professor of archaeology in Arts & Sciences, who collaborated on this study with researchers from several prominent institutions in China and Australia, including Guanghui Dong from Lanzhou University, who led the field expedition on the Loess Plateau. "The water management may have been achieved either by deliberate watering or by strategic planting in soils with higher water retention."

On the other hand, early farmers were able to grow the other new grain, barley, in a rainfed system as if it were just another kind of millet -- the locally domesticated and most commonly grown grain in northern China at the time -- without using any form of irrigation.

Liu published the study with Washington University graduate student Yufeng Sun. Other co-authors include Haiming Li and Petra Vaiglova, former members of Liu's lab group.

Introducing irrigation

Both wheat and barley were domesticated in an area known to archaeologists as the hilly flanks of the Fertile Crescent in southwest Asia, where they originally were grown as winter crops. Traditionally, farmers there sowed their seeds in autumn -- to avoid the summer drought period -- and harvested them in late spring or early summer before the next drought season.

When these Fertile Crescent crops, wheat and barley, were introduced to East Asia about 4,000 years ago, they would have encountered a markedly different climate compared with where they originated.

"Every summer, the East Asian monsoon brings rains from the Pacific Ocean to a region otherwise arid throughout the rest of the year. This environment is perfect for rainfed millet cultivation as these local grains are drought tolerant but need considerable water in the summer growing season," Liu said. "But it is a different story if you try to grow wheat there, not only because it is water demanding, but also the growing cycle doesn't match the rainy season."

Liu and his colleagues wanted to know: Did the farmers who sought to grow the new grains in northern China also introduce new systems of irrigation to support them?

"The introduction of a new irrigation system is something that scholars have speculated about, but now we have the technology to seek direct evidence," Liu said.

Using relatively new techniques, the actual growing conditions of past crops -- including past water and soil conditions during plant growth -- can be measured using the stable carbon and nitrogen isotope compositions of charred plant remains. These methods initially were established in plant science for research concerning environmental conditions of modern-day agriculture and have been subsequently applied to archaeological research.

Previous studies using similar approaches have shed significant light on early crop management in Europe and the Middle East. This research is one of the first attempts to apply it to East Asian monsoon environments with innovative questions.

For this study, the scientists identified more than 35,000 charred seed remains of cereal plants, including wheat, barley and millet, from more than 50 archaeological sites excavated on the Loess Plateau of China spanning a timeframe over eight millennia. Selected plant remains from this collection were radiocarbon dated and isotopically measured.

The results showed major differences between wheat and barley.

Despite the arid local environment, the majority of the wheat samples from all time periods had isotopic values above an optimal watering threshold, indicating that their growth was not limited by water availability.

"We see this in the Qijia culture period, when wheat and barley were just introduced to this region," Liu said. "The isotopic data of wheat show a significant level of water manipulation unambiguously since 4,000 years ago, indicating the new crop was introduced with water management strategies to support it."

Simple ditches can be powerful

This evidence alone does not necessarily imply large-scale irrigation, Liu is quick to point out; instead, wheat crops may have been strategically sown in areas with the best water availability, either close to local springs or in soils with high water retention.

"In those locations, small ditches to diffuse water is sufficient," Liu said. "This explains why there is no archaeological evidence of channels or other irrigation installations in the area until much later."

Barley, on the other hand, appears to have been grown on the dry hills of the Loess Plateau without a special water management approach -- a landscape and cultivation strategy that had been familiar to the Neolithic millet farmers since 8,000 years ago.

This and other evidence suggest to Liu and his collaborators that ancient farmers sought to optimize land use and crop yield by taking advantage of the different water demands of these two crops.

"Our results raise an awareness that the dispersal of domesticated crops and the knowledge of best using them can be traced independently across time and space," Liu said.

"Central to our inquiry is the tension between non-native crops and indigenous farming practices," he said. "When non-native innovations were adopted in another cultural and physical environment, they would have been transformed within the local context. How this happens is an enduring question that is relevant to globalization in the past and present."

This study resonates with other archaeological investigations led by Liu's research group, the Laboratory for the Analysis of Early Food-Webs at Washington University. For example, co-author Sun's previous work with Washington University graduate student Melissa Ritchey demonstrated a similar geographic decoupling of the dispersal of grains and cuisines, such that wheat and barley dispersed into ancient China 4,000 years ago, but the western grinding-and-baking cuisines did not. The eastern movement of these grains involved selections of phenotypic traits adapted to ancient China's cooking tradition of using steaming-and-boiling.

It has been a long time since some scholars assumed the association between the origin of bureaucracy and irrigation, and ancient China had been used as an example of "oriental despotism," according to Liu. The "hydraulic empire" hypothesis speculated that a centralized government structure that maintained power would have been derived from the need for flood control and irrigation.

Read more at Science Daily

Plant breeding: Using 'invisible' chromosomes to pass on packages of positive traits

The ideal crop plant is tasty and high-yielding while also being resistant to diseases and pests. But if the relevant genes are far apart on a chromosome, some of these positive traits can be lost during breeding. To ensure that positive traits can be passed on together, researchers at Karlsruhe Institute of Technology (KIT) have used CRISPR/Cas molecular scissors to invert and thus genetically deactivate nine-tenths of a chromosome. The traits coded for on this part of the chromosome become "invisible" for genetic exchange and can thus be passed on unchanged. The researchers have reported on their findings in Nature Plants.

Targeted editing, insertion or suppression of genes in plants is possible with CRISPR/Cas molecular scissors. (CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats.) This method can be used to make plants more resistant to pests, diseases or environmental influences. "In recent years, we were able for the first time to use CRISPR/Cas not only to edit genes but also to change the structure of chromosomes," says Professor Holger Puchta, who for 30 years has been researching applications for gene scissors with his team at KIT's Botanical Institute. "Genes are linearly arranged along chromosomes. By changing their sequence, we were able to show how desired traits in plants can be separated from undesired ones."

Now the researchers have been able to prevent the genetic exchange that is normally part of the hereditary process but can break the links between traits. "We can shut down a chromosome almost completely, making it seem invisible, so that all traits on that chromosome can be passed on in a package," says Puchta. Until now, if a plant's traits were to be passed on together, the genes for those traits needed to be close to each other on the same chromosome. If such genes are spread farther apart on a chromosome, they are usually separated during inheritance, so a beneficial trait can be lost during the breeding process.

Learning from Nature: Chromosome Engineering Prevents Genetic Exchange

In their research, the scientists followed nature's example. "These reversals, or inversions -- a kind of genetic invisibility -- also occur frequently on a smaller scale in wild and cultivated plants. We've learned from nature and have applied and extended our knowledge about the natural process," says Puchta.

In collaboration with Professor Andreas Houben from the Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Puchta and his team inverted nine-tenths of a chromosome in the model organism Arabidopsis thaliana (thale cress). Only at the ends of the chromosome did the genes retain their original sequence. "With these fragments, the chromosome can be passed on to the next generation just like the other chromosomes and is not completely lost," says Puchta.

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Growing cereal crops with less fertilizer

Researchers at the University of California, Davis, have found a way to reduce the amount of nitrogen fertilizers needed to grow cereal crops. The discovery could save farmers in the United States billions of dollars annually in fertilizer costs while also benefiting the environment.

The research comes out of the lab of Eduardo Blumwald, a distinguished professor of plant sciences, who has found a new pathway for cereals to capture the nitrogen they need to grow.

The discovery could also help the environment by reducing nitrogen pollution, which can lead to contaminated water resources, increased greenhouse gas emissions and human health issues. The study was published in the journal Plant Biotechnology.

Nitrogen is key to plant growth, and agricultural operations depend on chemical fertilizers to increase productivity. But much of what is applied is lost, leaching into soils and groundwater. Blumwald's research could create a sustainable alternative.

"Nitrogen fertilizers are very, very expensive," Blumwald said. "Anything you can do to eliminate that cost is important. The problem is money on one side, but there are also the harmful effects of nitrogen on the environment."

A new pathway to natural fertilizer

Blumwald's research centers on increasing the conversion of nitrogen gas in the air into ammonium by soil bacteria -- a process known as nitrogen fixation.

Legumes such as peanuts and soybeans have root nodules that can use nitrogen-fixing bacteria to provide ammonium to the plants. Cereal plants like rice and wheat don't have that capability and must rely on taking in inorganic nitrogen, such as ammonia and nitrate, from fertilizers in the soil.

"If a plant can produce chemicals that make soil bacteria fix atmospheric nitrogen gas, we could modify the plants to produce more of these chemicals," Blumwald said. "These chemicals will induce soil bacterial nitrogen fixation and the plants will use the ammonium formed, reducing the amount of fertilizer used."

Blumwald's team used chemical screening and genomics to identify compounds in rice plants that enhanced the nitrogen-fixing activity of the bacteria.

Then they identified the pathways generating the chemicals and used gene editing technology to increase the production of compounds that stimulated the formation of biofilms. Those biofilms contain bacteria that enhanced nitrogen conversion. As a result, nitrogen-fixing activity of the bacteria increased, as did the amount of ammonium in the soil for the plants.

"Plants are incredible chemical factories," he said. "What this could do is provide a sustainable alternative agricultural practice that reduces the use of excessive nitrogen fertilizers."

The pathway could also be used by other plants. A patent application on the technique has been filed by the University of California and is pending.

Read more at Science Daily

Critical benefits of snowpack for winter wheat are diminishing

University of Minnesota scientists are partnering with a global team to study the complex effects of climate change on winter crops.

Warming winters may sound like a welcome change for some farmers because the change in temperature could reduce freezing stress on plants and create more ideal conditions for growing overwinter cash crops and winter cover crops. However, when looking at climate change from a cross-seasonal perspective and accounting for declining snowpack, researchers are finding that the whole picture isn't so sunny.

Reduced snow may result in more exposure of winter crops to freeze and could mean greater risks for agricultural drought.

In a new study published in Nature Climate Change, Zhenong Jin, Ph.D., an assistant professor in the Department of Bioproducts and Biosystems Engineering at the University of Minnesota, led an international team in researching the implications that could be associated with warmer winters and declining snowpack, using winter wheat (the largest winter crop in the U.S.) as an example.

"Although the implications of changes in snow for agricultural irrigation are beginning to be understood, the consequences of such for predominantly rainfed winter crops such as winter wheat remain largely unknown. There might be risks for being overoptimistic about growing overwinter crops under climate change," said Jin.

Researchers used panel regression, a powerful statistical method to analyze repeated observations over time, to attribute the interannual variability of winter wheat yield to multiple interactive environmental factors. These factors included cold season freezing degree days, growing degree days, rainfall and snowfall during the growing season and snow cover fraction during frozen days.

The researchers found:
 

• From 1999-2019, snow cover insulation weakened yield losses due to freezing stress by 22%.
• Projections show that future reduced snow cover could offset up to one-third of the yield benefit from reduced frost.

"Our study highlighted the potential freezing risk in winters with decreased snow cover, especially when seedlings were exposed to comparatively warmer conditions that caused loss of winter-hardiness, which can cause significant yield losses of winter crops," said Peng Zhu, Ph.D., a Researcher from the Climate and Environment Sciences Laboratory of the Pierre Simon Laplace Institute, who co-led this study.

This research will help inform breeders as they consider the complex tradeoffs among warming, reduced snowpack and occasional freezing threats when developing climate-smart cultivars.

These results also highlight the necessity of improving the representation of snow associated processes in crop models to better evaluate climate change effects and adaptation potential in cropping systems.

"It is worth noting that in some cropping systems freezing stress is appreciated, since it helps farmers control pests and diseases and snow is even removed or at least made more compact by farmers to increase the freezing of the soil," said Jin. "When data becomes available, future studies might also need to account for the influence of snow on pests and diseases to comprehensively understand what future changes in snowpack mean for the cropping system."

Read more at Science Daily

Suitable growing regions for coffee, cashews, and avocados predicted to shift as Earth warms

A new analysis predicts that, as climate change progresses, the most suitable regions for growing coffee arabica, cashews, and avocados will decline in some of the main countries that produce these crops. Roman Grüter and colleagues at Zurich University of Applied Sciences, Switzerland, present these findings in the open-access journal PLOS ONE on January 26, 2022.

Coffee, cashews, and avocados are important crops for consumers and for tropical small-scale farmers around the world. Extensive research suggests that climate change will reduce suitability for growing coffee arabica—the dominant coffee species—in most regions where it is currently grown. However, such studies have not considered land and soil characteristics that could also impact suitability. Meanwhile, no studies have addressed how climate change will impact avocado and cashew suitability at a global scale.

To address these knowledge gaps, Grüter and colleagues combined climate change projections and soil factors to computationally model and predict how suitable different regions worldwide will be for growing coffee, cashews, and avocados in 2050. They used projections from 14 global climate models under three different future emission scenarios and incorporated land and soil requirements for the crops, such as pH, texture, and slope.

The analysis predicts that some regions will become more suitable and some less suitable for each crop. Coffee is the most susceptible of the three, with predicted declines in suitability in all major producing regions, including Brazil, Vietnam, Indonesia, and Colombia. For cashews, highly suitable regions are predicted to decrease in some major producing countries, including India, Côte d’Ivoire, and Benin. Suitable areas for avocados will also decline for some major producers, such as the Dominican Republic, Peru, and Indonesia.

Meanwhile, areas suitable for all three crops may expand at higher altitudes and latitudes, especially for cashews and avocados. Areas with greater future suitability are located in regions such as the United States, Argentina, China, and East Africa.

These findings suggest the need for climate change adaptations in major producing countries, such as breeding for varieties adapted to higher temperatures or drought. Strategies will also be needed to mitigate the environmental impact of any expansion to new locations.

Read more at Science Daily

Study challenges evolutionary theory that DNA mutations are random

A simple roadside weed may hold the key to understanding and predicting DNA mutation, according to new research from University of California, Davis, and the Max Planck Institute for Developmental Biology in Germany.

The findings, published January 12 in the journal Nature, radically change our understanding of evolution and could one day help researchers breed better crops or even help humans fight cancer.

Mutations occur when DNA is damaged and left unrepaired, creating a new variation. The scientists wanted to know if mutation was purely random or something deeper. What they found was unexpected.

"We always thought of mutation as basically random across the genome," said Grey Monroe, an assistant professor in the UC Davis Department of Plant Sciences who is lead author on the paper. "It turns out that mutation is very non-random and it's non-random in a way that benefits the plant. It's a totally new way of thinking about mutation."

Researchers spent three years sequencing the DNA of hundreds of Arabidopsis thaliana, or thale cress, a small, flowering weed considered the "lab rat among plants" because of its relatively small genome comprising around 120 million base pairs. Humans, by comparison, have roughly 3 billion base pairs.

"It's a model organism for genetics," Monroe said.

Lab-grown plants yield many variations

Work began at Max Planck Institute where researchers grew specimens in a protected lab environment, which allowed plants with defects that may not have survived in nature be able to survive in a controlled space.

Sequencing of those hundreds of Arabidopsis thaliana plants revealed more than 1 million mutations. Within those mutations a nonrandom pattern was revealed, counter to what was expected.

"At first glance, what we found seemed to contradict established theory that initial mutations are entirely random and that only natural selection determines which mutations are observed in organisms," said Detlef Weigel, scientific director at Max Planck Institute and senior author on the study.

Instead of randomness they found patches of the genome with low mutation rates. In those patches, they were surprised to discover an over-representation of essential genes, such as those involved in cell growth and gene expression.

"These are the really important regions of the genome," Monroe said. "The areas that are the most biologically important are the ones being protected from mutation."

The areas are also sensitive to the harmful effects of new mutations. "DNA damage repair seems therefore to be particularly effective in these regions," Weigel added.

Plant evolved to protect itself

The scientists found that the way DNA was wrapped around different types of proteins was a good predictor of whether a gene would mutate or not. "It means we can predict which genes are more likely to mutate than others and it gives us a good idea of what's going on," Weigel said.

The findings add a surprising twist to Charles Darwin's theory of evolution by natural selection because it reveals that the plant has evolved to protect its genes from mutation to ensure survival.

"The plant has evolved a way to protect its most important places from mutation," Weigel said. "This is exciting because we could even use these discoveries to think about how to protect human genes from mutation."

Future uses

Knowing why some regions of the genome mutate more than others could help breeders who rely on genetic variation to develop better crops. Scientists could also use the information to better predict or develop new treatments for diseases like cancer that are caused by mutation.

"Our discoveries yield a more complete account of the forces driving patterns of natural variation; they should inspire new avenues of theoretical and practical research on the role of mutation in evolution," the paper concludes.

Co-authors from UC Davis include Daniel Kliebenstein, Mariele Lensink, Marie Klein, from the Department of Plant Sciences. Researchers from the Carnegie Institution for Science, Stanford University, Westfield State University, University of Montpellier, Uppsala University, College of Charleston, and South Dakota State University contributed to the research.

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