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New avenues for improving modern wheat

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Since the Agricultural Revolution about 12,000 years ago, humans have been selectively breeding plants with desirable traits such as high grain yield and disease resistance. Over time, Triticum aestivum, otherwise known as bread wheat, has emerged as one of the world’s most important crops. Together with the growing human population and the changing climate, the demand for wheat with a higher yield and additional resilience is increasing.

However, for a few years now the average yield increase of wheat is stagnating. In a new international study, the genetic diversity of 487 wheat genotypes originating from large parts of the world has been catalogued and contextualised with agronomic traits. The map of this rich pool of genetic diversity in bread wheat highlights our current knowledge of the ancestry of wheat and opens new avenues within modern selective wheat breeding.

The evolution of wheat is a complex history of hybridisation and gene flow events, which led to the allohexaploid (with six sets of chromosomes) Triticum aestivum, the species of wheat that we know nowadays as bread wheat. The modern bread wheat originated in the Fertile Crescent about 10,000 years ago and its genepool has been shaped by humans as a result of domestication and cultivation. Today, high-yielding varieties of Triticum aestivum can be found all over the world, each variety adapted to the particular environment it is being grown in, making wheat one of the world’s three most important crop species for human calories and protein supply.

The growing demand for wheat, the onset of global warming, and the transitioning of Western farming away from intensive agriculture, are exerting pressure on plant breeders to further adapt and improve modern bread wheat species. However, in order to select and breed new wheat cultivars with new and improved traits, plant breeders require plants with genetic variation for selection and combination during the breeding process. A new international study of bread wheat has now revealed knowledge of an extensive and rich gene pool for future breeding improvements of Triticum aestivum.

In this study, the exomes of 487 wheat genotypes from 68 countries around the world, including landraces, cultivars, as well as modern varieties, were sequenced. The Leibniz Institute of Plant Genetics and Crop Plant Research (IPK Gatersleben) was able to contribute to this by providing wheat samples from the Federal Ex situ Gene Bank. Utilising the Refseqv1.0 reference sequence of the bread wheat landrace “Chinese Spring”, which had been published by the “International Wheat Genome Sequencing Consortium” (IWGSC) in 2017, the collaborating researchers were able to compile a comprehensive overview of wheat genomic diversity at the genic, chromosomal and subgenomic levels. This enabled them to refine and expand the model of wheat evolution and to decipher the genetic origins of modern day wheat species. As such, the durum wheat lineage was confirmed as the most likely ancestor of today’s bread wheat cultivated germplasm. Moreover, by investigating the selection footprints of wheat, the scientists showcased the effects of range expansion and allelic variants selected since the beginning of wheat domestication.

The reported data is another step towards the assembly of the “pan genome” of wheat – the description of all the genes and genetic variations within wheat, which will be a valuable resource for plant researchers and wheat breeders alike. However, the study as it stands already reveals a rich genetic data resource, which can be utilised for improving genetic traits in bread wheat, from environmental adaptation to improved yield and disease resistance. Moreover, the results illustrate our current knowledge of the ancestry of bread wheat, highlighting our cultural history as farmers and plant breeders.

Read the paper: Nature Genetics

Article source: Leibniz Institute of Plant Genetics and Crop Plant Research

Image: Julie Himpe/IPK

Close relatives can coexist: two flower species show us how

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Scientists have discovered how two closely-related species of Asiatic dayflower can coexist in the wild despite their competitive relationship. Through a combination of field surveys and artificial pollination experiments, the new study shows that while reproductive interference exists between the two species, Commelina communis and Commelina communis forma ciliata, both can counter the negative effects of this interference through self-fertilization.

These findings offer a different perspective on theories surrounding co-existence, and suggest a new significance for plants’ ability to self-fertilize. The finding was made by Japan Society for the Promotion of Science Research Fellow Koki Katsuhara and Professor Atushi Ushimaru, both part of the Kobe University Graduate School of Human Development and Environment, and it was published in Functional Ecology.

The ability of plant species to coexist has long fascinated scientists. When species with shared pollinators flower at the same time in the same place, it’s thought that the reproductive interference caused by pollinators makes it hard for these plant species to coexist. Reproductive interference occurs when pollen from another species is deposited on the pistil (female reproductive part of the flower), and competition between pollen tubes causes a decrease in seed production.

The two species of Asiatic dayflower Commelina communis (Cc) and Commelina communis forma ciliata (Ccfc), commonly found in the fields and roadsides of Japan, produce very similar-looking flowers and attract the same pollinators. First the scientists looked at the two species in the wild. They found that pollinators such as bees and hoverflies visited both species indiscriminately, and both species showed a decrease in seed production as the other species’ number of flowers increased. In other words, mutual reproductive interference was occurring. The surveys also suggested that Cc is less affected by this interference than Ccfc. This is consistent with the dominance of Cc in the areas surveyed.

By combining fieldwork surveys with artificial pollination experiments, the team discovered that self-pollination helps to reduce the negative impact of reproductive interference. Even when one species was heavily impacted by the large number of flowers produced by the other species, through self-pollination both species managed to produce enough seeds to survive. Cc was able to produce more seeds than Ccfc through self-pollination, which is probably the cause of the asymmetrical production between the species.

We would expect Cc to wipe out Ccfc through reproductive interference, but in fact both species can be found growing in the wild. Katsuhara and Ushimaru propose that the distribution of these two species plays an important role in their ability to coexist despite the strong competition between them. While most areas are dominated by Cc, in some areas Ccfc outnumbers Cc, giving it the advantage. Even when it is almost totally surrounded by Cc, Ccfc can still leave some seeds through self-pollination.

Scientists believe that self-pollination developed so that plants can still produce seeds even when pollinators are scarce. This study suggests that the self-pollination can also mitigate the negative effects when pollen from other species hinders seed production. Self-pollination could also be used to explain the coexistence of plants who share pollinators. This finding marks a step forward in shedding light on species coexistence, and gives a new perspective to the evolutionary background of self-pollination.

Read the paper: Functional Ecology

Article source: Kobe University

Image: Kobe University

New discovery could alleviate salty soil symptoms in food crops

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New research published in Nature Scientific Reports has found that a hormone produced by plants under stress can be applied to crops to alleviate the damage caused by salty soils. The team of researchers from Western Sydney University and the University of Queensland identified a naturally-occurring chemical in plants that reduces the symptoms of salt stress in plants when applied to soil, enabling the test plants to increase their growth by up to 32 times compared with untreated plants.

Salinity is a huge issue across the world, affecting more than 220 million hectares of the world’s irrigated farming and food-producing land. Salinity occurs when salty irrigation water is repeatedly applied to crops, leading to progressively increasing levels of salt in the soil which reduces crop yields, increases susceptibility to drought and damages soil microbiology. Scientists have long tried to find ways to breed salt-tolerance or develop methods that remove salt, and this new research is promising in its potential ability to reduce the damage in crop plants that results from salt.

“We identified a compound called ACC that occurs naturally in plants when they become stressed by drought, heat or salty conditions,” said Dr Hongwei Liu, Postdoctoral Fellow in Soil Biology and Genomics at the Hawkesbury Institute for the Environment at Western Sydney University.

By applying ACC to crops planted into salty soils, it created conditions that prevented the formation of the compounds that cause plant damage under salty conditions and increased beneficial soil enzyme and microbial activity. These effects enabled the plants to cope with the salt and increased the growth of lettuce plants by nearly five times and model plants by over 30 times.

“There is very significant potential for this compound in enabling us to manage crop production in otherwise-unusable soils,” said Professor Peer Schenk School of Agriculture and Food sciences at the University of Queensland.

“Growers have traditionally used a range of long-term and slow-acting materials such as gypsum, manures, tillage and other methods to reduce the exposure of plants to the salts in soils but these are costly, frequently ineffective and work to limited benefits over years or decades”, he said.

One of the major benefits of ACC is that it is naturally produced by plant roots and therefore contributes to long-term soil health, plant-microbe relationships and carbon storage.

Read the paper: Nature Scientific Reports

Article source: Western Sydney University

Image: Western Sydney University

Early spring: Predicting budburst with genetics

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Although climate skeptics might find it hard to believe with this year’s endless snow and freezing temperatures, climate change is making warm, sunny early springs increasingly common. And that affects when trees start to leaf out. But how much? In a study published in Methods in Ecology and Evolution, Simon Joly, biology professor at Université de Montréal and Elizabeth Wolkovich, an ecology professor at University of British Columbia, showed that a plant’s genetics can be used to produce more accurate predictions of when its leaves will burst bud in spring.

“We discovered that when species and individual specimens within a species are very similar genetically, they tend to respond more similarly to environmental signals than those that are genetically dissimilar,” said Joly, who is also a botanical researcher at the Jardin botanique de Montréal.

He came to this conclusion after responding to a call sent out by Elizabeth Wolkovich, a professor at the University of British Columbia who previously taught at Harvard University and studies how trees respond to climate change. She wanted to include genetics, one of Joly’s areas of expertise, in her work to see if it could help better predict budburst.

They chose 10 tree and shrub species that are relatively common in Massachusetts and Quebec, including striped maple, American beech, northern red oak and specific types of honeysuckle, poplar and blueberry. Branches were collected from Harvard Forest in Massachusetts and UdeM’s Station de biologie des Laurentides in January, once the trees and shrubs had been cold long enough for leaves to burst bud—given the right conditions.

“There are three main environmental signals that affect budburst: the length of time they’ve spent in the cold, warm temperatures and hours of daylight,” said Elizabeth Wolkovich, who studies the influence of climate change on trees and other plants. “Once collected, the branches were kept chilled and sent to Harvard’s Arnold Arboretum, where they were then placed in special growth chambers with controlled temperatures and hours of daylight.”

The experiment was carried out with 8- and 12-hour-long days and daytime temperatures of 15 and 20 degrees Celsius.

The trees adapted

The experiment showed that a 5-degree increase in temperature causes leaves to burst bud 20 days earlier than average, though the impact on each species can vary considerably. Furthermore, more hours of daylight moved budburst up by about 12 days.

However, these estimates become more accurate once genetic information from the trees and shrubs has been factored in.

“This finding held true even though we didn’t find major genetic differences between individual specimens of a single species between the two regions,” said Joly. “Tree genes move around relatively quickly through pollen, so some individual specimens in Massachusetts could be genetically more closely related to specimens in Quebec than to other specimens in Massachusetts.”

Even though it’s still very hard to tell how climate change will affect spring, this study shows that plants react strongly to differences in climate and that their genetics help determine how well they adapt to these changes.

These findings open the door to a wide range of new studies

“We’ll certainly consider genetics in future studies. For example, we may look at whether certain individual specimens within a species are better equipped to adapt to climate change and why,” said Wolkovich. “That’s how plant species might be able to adapt to what’s coming. But of course this depends on how extreme the changes to our climate actually are, which remains an open question given current carbon emissions.”

Joly also wonders how the ecosystem as a whole, including the insects that eat leaves, will react to higher temperatures. “Will they react in the same way as trees? These are the extremely complex questions that people are beginning to ask and that we have to study jointly with other researchers from different disciplines.”

Read the paper: Methods in Ecology and Evolution

Article source: Université de Montreal

Image: Tim Savas

Can sweet potatoes save the world?

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Some foods are known as seasonal wonders, making an appearance only once or twice a year when families gather for holiday feasts. Cranberry sauce, pecan pie, eggnog. Sweet potatoes, typically with tiny marshmallows roasted on top, were once on that list. But sweet potatoes are on the rise. They have become increasingly recognized as a superfood packed with essential vitamins and nutrients, and are now enjoyed throughout the year — in upscale restaurants, as a healthier alternative to French fries, and in products as varied as vodka, sausage and muffins.

Behind that rise is a remarkable success story with its roots at NC State, one that reaches into the familiar farms of eastern North Carolina and to the often forgotten corners of a handful of African nations. It is a story of science and salvation, of a pair of breeders who defied ridiculous odds to develop a new sweet potato variety that rescued the industry in North Carolina. It is also a story that holds out promise for the future, well beyond the shores of North Carolina and its acres of sweet potatoes. The work of a professor at NC State could transform the way sweet potatoes are eaten in several African countries, improving the health of young children and their mothers and creating new economic opportunities in Africa’s bustling cities and smallest villages.

Antonio Magnaghi is among those in Africa banking on sweet potatoes. He is well on his way to turning his small bakery on a crowded industrial street in downtown Nairobi, Kenya, into a thriving business that sells sweet potato muffins, fries and other products in the country’s top hotels, markets and coffee shops.

“The possibilities,” Magnaghi says with an irrepressible grin, “they are endless with sweet potato.”

It was not that long ago, though, that the outlook for sweet potatoes was grim at best. Less than two decades ago, sweet potato farmers across eastern North Carolina were telling their kids to find another type of work because they couldn’t count on a decent crop of sweet potatoes. They were primarily planting a variety known as Beauregard that was developed in Louisiana, and it was not well suited to North Carolina’s soil and climate. There were too many unpleasant surprises — like getting your first look at a bad poker hand — when farmers dug up their sweet potatoes each fall. They kept finding odd shapes and sizes that wouldn’t sell in grocery stores. Or, as one farmer puts it, Beauregard sweet potatoes were “as ugly as homemade soap.” Without a new variety, fewer and fewer sweet potatoes were going to be grown in North Carolina. “Our livelihood was at stake,” says Jerome Vick, the patriarch of a large family farm in Wilson, N.C.

Then, in 2005, breeders at NC State hit the jackpot. They came out with a sweet potato variety they called Covington, which had begun as a botanical seed in 1997 and progressed through years of field trials. Within a few years, Covington was nearly all anyone grew in North Carolina. Year after year, from one field to another, it could be counted on to produce a high percentage of what are known as “number ones,” with the familiar shape, size and look to be sold in grocery stores and farmers’ markets. By 2017, the amount of sweet potatoes grown in North Carolina had nearly doubled and the state had reclaimed its place as the leading producer of sweet potatoes in the United States. Jim Jones, who grows about 1,500 acres of sweet potatoes in Nash County, says Covington was “the best thing that’s happened in the sweet potato business.”

The combined efforts of NC State researchers, professors and extension agents, working closely with farmers and an engaged trade group, have transformed sweet potatoes into a year-round economic powerhouse that is now shipped from North Carolina to Europe and other corners of the globe. Some farmers have described it as a perfect example of the work that a land-grant university such as NC State should do. “We just couldn’t operate without NC State,” says Pender Sharp ’71, a fifth-generation farmer in Sims, N.C., about an hour’s drive east of Raleigh.

But that’s only part of NC State’s sweet potato story.

Half a World Away

Craig Yencho is crouching in a field of sweet potatoes in the remote northwest corner of Uganda, not far from a massive tent camp that is home to thousands of refugees from South Sudan. He has driven more than seven hours from Kampala, the country’s chaotic capital city, across the Nile River and past a pack of wild baboons and a couple of wandering elephants to get to a research farm in the town of Arua. He is struggling with a stick to dig into the dirt, which has been baked rock hard by the unforgiving equatorial sun and the delayed onset of the rainy season. What he finally pulls out of the ground is a scrawny excuse for a sweet potato. It is also riddled with holes that are signs of weevils, a small but pervasive pest that can wipe out a crop.

Yencho, a William Neal Reynolds Distinguished Professor and leader of NC State’s sweet potato and potato breeding and genetics program, was one of the masterminds behind Covington, the variety now grown throughout North Carolina. He also leads an effort, fueled by a $12 million grant from the Bill and Melinda Gates Foundation, to bring molecular science to sweet potato breeding programs in Uganda and a handful of other sub-Saharan countries in Africa. His ultimate goal is twofold — to use sweet potatoes to increase economic opportunities and to get sweet potatoes’ nutrients into the bellies of children and pregnant women who suffer from such serious vitamin A deficiencies that they are in danger of going blind.

Sweet potatoes are already a staple of the diet for many families in Uganda, who eat them steamed in banana leaves or simply boiled, sometimes with every meal. But most of the sweet potatoes grown in Africa would be unfamiliar to American consumers. Instead of orange, they have white, cream-colored or yellow flesh, and are not as sweet or soft as their American cousins. They also don’t have all the nutrients found in orange-fleshed sweet potatoes.

But changing consumer preferences may be the easy part of Yencho’s challenge — early promotional efforts touting the health benefits of orange foods such as sweet potatoes and mangoes have created some converts. “Kids are attracted by the orange color,” says Robert Mwanga ’01, Ph.D, a Ugandan scientist who won the World Food Prize in 2016 for his pioneering work to promote orange-fleshed sweet potatoes in his country. “Also, the softer the food is, the better it is for kids. It’s easier for them to eat.”

The bigger challenge is breeding new varieties of orange-fleshed sweet potatoes that can be grown in Uganda. Weevils take advantage of dry, cracked soil brought on by drought (and a lack of irrigation) to burrow their way into growing sweet potatoes, and wipe out more than 70% of the crop in most years. “Everywhere that sweet potato is grown [in Uganda], you will find weevils,” says Mwanga. And orange-fleshed sweet potatoes, which typically have less starch and are therefore less dense than most of the sweet potatoes grown in Uganda, are softer and easier for weevils to burrow into. “We still have a long way to go,” Mwanga says, “to get something that farmers can leave out in the field and not worry about the weevil.”

As insurmountable as the challenges may seem, Yencho is undaunted. He laughs when he is asked during a visit to Uganda and Kenya last year if it feels like he is forever pushing a heavy rock up a steep hill, like a modern-day, gray-haired Sisyphus. “Yeah, it can feel like that sometimes,” he says. But Yencho prefers a different outlook, one that reflects an optimism dating back to his wanderlust days as a young Peace Corps volunteer in St. Kitts and Nevis.

It is an optimism that focuses less on the big picture in favor of countless small victories. It takes into account the Ugandan breeders he has trained (such as Mwanga and Benard Yada ’14, Ph.D., who runs the government’s sweet potato research efforts) as graduate students at NC State. It takes into account the scientists he works with on a bucolic research campus in Nairobi, Kenya, to develop a program using advanced molecular breeding techniques that will help sweet potato farmers in Africa, North Carolina and elsewhere. It takes into account home-grown entrepreneurial efforts he has seen in Africa that embrace the economic and health benefits that come with orange-fleshed sweet potatoes.

“I like to think in terms of pebbles,” Yencho says, “and how a pebble tossed into a pond creates ripples.”
$170 Million in Economic Impact

Sweet potatoes mean cash for North Carolina farmers, and the crop has a huge annual economic impact in the state.

He sees some of those ripples during his visit to the farm in Arua, where researchers have been working with sweet potatoes for only three years. “The field looks beautiful,” he says as he surveys the scene with Yada and a group of Ugandan breeders traveling with him and some of the farm staff. “The rows are well laid out. Your weed management is really exceptional.” He detects what he calls “drought damage,” but wonders about other damage to the crops. “That’s goat damage,” someone tells him. “Say what?” Yencho asks. “Goat damage,” he is told again. Yencho laughs. “I’m an animal lover,” he says, “so that’s OK.”

It Takes Time

Ken Pecota is crouching in a field of sweet potatoes on a research farm in Clinton, N.C. A flap on his cap protects his neck from the sun as he works his way down dusty rows to check on several varieties being tested. Pecota, a sweet potato researcher and breeder at NC State, was also one of the breeders behind Covington. It was clearly the signal achievement of his career, but he is determined to develop other varieties that will find their way into farmers’ fields. Some are for niche markets, such as organics, while others are more suitable for processing into fries, chips or other uses. And there are no guarantees that problems won’t eventually develop with the Covington breed.

“If you’re ever satisfied as a breeder, you need to retire,” he says. “There’s always something you can make better.”

The varieties he’s testing today have already shown some promise, but there are far more tests to be done before any conclusions can be reached. They sit on top of the dirt, having been dug up earlier, and Pecota is conducting the most basic tests before the potatoes are sent to the lab for further analysis. “See, this guy rotted,” he says as he grabs a sweet potato. “That’s not a good sign.” But he also notes some positive signs: “They’ve got good uniformity, right? They’re all kind of the same shape. There’s a nice lightness, a really nice finish to it. The skin texture is beautiful.” He slices into some of the sweet potatoes and takes a bite, and estimates the amount of starch (an important consideration for varieties bred primarily for processing into fries or chips). “I know that one’s got a medium starch,” he says at one point.

The practiced ease with which Pecota approaches his work masks the fact that it is incredibly difficult to breed sweet potatoes, be it in North Carolina or in Africa. It’s easy enough to cross two different varieties of sweet potatoes and come up with a new, distinctive variety — as long as you don’t care too much about how it turns out. Sweet potatoes have a much more complex genetic makeup than most vegetables, fruits and grains. Sweet potatoes are a hexaploid, which means they have six sets of chromosomes.

So it’s difficult to get the desired mix of traits. NC State’s breeders track 45 different traits — resistance to disease, drought tolerance, shape, color and size, to name just a few — in the sweet potato varieties they work with. It takes years of trial and error to test new varieties, and the overwhelming majority end up having some sort of fatal flaw that makes them ill-suited for farming or processing. Yencho and his team start every year with 60,000 new varieties, knowing that most of them will fall short at some point during seven (or more) years of field tests. At times, the process can seem downright cruel — a couple of years after releasing Covington, Yencho and Pecota released another variety named Hatteras that had performed well in all the field tests. But after farmers started planting it, Hatteras developed something called internal necrosis, which creates brown flecks in the flesh. Within two years, no one was growing Hatteras. Pecota was once curious about just how difficult his job was, and calculated that there is as much as a one-in-two million chance of breeding a sweet potato that satisfies the criteria they try to meet.

“If you look at that number, “ Pecota says, “you’ll say, ‘That’s it, I quit.’”

Pecota is joking. As a kid in suburban New Jersey, he loved working on puzzles of all sorts — jigsaw, word, number — and he brings that same passion to his work as a breeder. “That’s exactly what breeding is,” he says. “It’s a big puzzle.”

Life cycle of a sweet potato

  • STARTING: Sweet potatoes are not started from seed. Instead, they are grown from vine cuttings that are called sprouts or slips. Some farmers start their sprouts in greenhouses, but others grow sprouts by “bedding” small sweet potatoes in March. Whole sweet potatoes are put on top of the ground and then covered with a thin layer of soil and plastic.
  • TRANSPLANTING: Sprouts are cut and transplanted — either from a greenhouse or “bedding” field — to another field in May and June.
  • GROWING: It takes 90–120 frost-free days to grow a sweet potato. They grow under the ground.
  • HARVESTING: The harvesting of sweet potatoes typically starts in August. Tractors are used to flip them on top of the ground and then, because the thin skin can be easily scarred, they are harvested by hand. They are graded and sorted according to their size.
  • CURING: Most sweet potatoes are cured for 4–7 days at 80–85 degrees so that they can then be stored for up to a year at 55 degrees with 85–90% humidity and adequate ventilation.

Efforts are further complicated by the sweet potato’s status as what is considered an “orphan crop.” Unlike crops like corn, wheat and rice, there have been no big corporations involved with sweet potatoes, which has historically been considered a subsistence crop for poor people. That means no corporate dollars for research and technology, and it is why sweet potatoes lag behind other crops when it comes to the latest, molecular-based breeding programs. “Sweet potatoes are under-researched,” says Mercy Kitavi, a molecular breeder who works in Kenya with the program Yencho is leading. “When you look at the complex genetics of sweet potatoes, everybody is like, ‘Not me.’ We don’t know the answer to seemingly simple questions like the genetics of beta carotene.”

Kitavi is working with Yencho and others to correct that. Her labs are housed on a research campus that is fenced off from the chaos and poverty that abounds in Nairobi. Here, she spends her days extracting the DNA from sweet potato varieties, which is then sent to NC State’s Genomic Sciences Laboratory to be sequenced. It is all part of an effort to develop a set of genetic markers that could be used to bring more predictability to the process. Such knowledge could be used, for example, to reduce the 60,000 new varieties that NC State’s program starts on the testing regimen each year to as few as 10,000–12,000. That’s less time and money spent on the front end, and a greater likelihood of positive results. “We need to speed up variety development,” Yencho says.

In part, that’s because there is not likely to be just one variety — like Covington in North Carolina — that will be the answer to the varying conditions throughout Africa. “Covington wouldn’t work in Africa,” Yencho says. “You have to breed African varieties in an African context.”

Cultural Differences

In Uganda, virtually everyone is a farmer. Dried sweet potatoes — none of them orange —are readily available from roadside vendors. Yencho’s team stops at one point on the highway from Soroti to Kampala to talk with a group of women selling buckets of dried sweet potato slices for 5,000 Ugandan shillings a bucket — that’s about $1.33. The women, joined by their children and husbands, lead the visitors into their cluster of a half dozen huts to show off a large rock embedded in the ground — it is where they dry the sweet potatoes grown in a small plot nearby. (It is also, they say while pointing to an indention in the rock, a place where Jesus once stood.)

Mwanga, who led the early push for orange-fleshed sweet potatoes in his country, estimates that roughly 90% of households have their own farm, which may be no more than a half-acre. That’s 2 million households. Compare that to North Carolina, where fewer than 400 farmers grow sweet potatoes, and most of them are part of a commodity group that works with the university and shares information. Extension agents spread throughout the state make it relatively easy to spread the word of new developments or problems for sweet potatoes. In Uganda, there are more than 50 different languages spoken. That means there are more than 50 different ways to say sweet potato, from “acok” in Ateso, the language spoken by the people showing off their drying rock, to “maku” in Lugbara. Communication is difficult at best.

Bonny Oloka ’18, Ph.D., finished his graduate work with Yencho last year and returned to Uganda to work as a sweet potato breeder. He never ate orange-fleshed sweet potatoes growing up in Kampala, and says the challenge of replacing other sweet potatoes in his country is great. “Every region you go to you will find completely different people,” he says. “The language is different, the cultures are different, the foods are different.”

But Oloko, who was trained as a biochemist, chose to go into breeding because he believes in the power of food to improve the health of his fellow Ugandans. “I think it’s attainable,” he says, “because 15 years ago there was almost no orange-fleshed sweet potato in Uganda. I didn’t have it. My parents could not get it. But now we know where to get it.”

Likewise, Sadik Kassim, director of research at the government farm in Arua, says there is plenty of interest in orange-fleshed sweet potatoes in his region along the Nile River. He estimates that 15% of the households in the region — compared to 5% in the rest of the country — grow and eat orange-fleshed sweet potatoes. “West Nile is where sweet potato can make a difference,” he implores Yencho during a meeting before heading out into the fields. “Our market is there. Our problem is if we can produce a supply of good and clean vines [for growing sweet potatoes].”

Yencho appreciates the sentiment, but points out some of the region’s challenges, including a lack of irrigation and storage capacity for harvested sweet potatoes. “This district has been ignored,” he says.

Sweet Success

While they are not as obvious as the success that farms in eastern North Carolina have had with sweet potatoes, encouraging signs can be found throughout Africa. Jan Low, an agricultural economist who has promoted the health benefits of orange-fleshed sweet potatoes throughout Africa, says Rwanda, Malawi and Mozambique have all seen an increase in the consumption of orange-fleshed sweet potatoes. “Those are all very important countries that have significant vitamin A deficiency problems,” Low said during a visit to the research campus in Nairobi.

One such success story can be found in downtown Nairobi, on the second floor of a nondescript building on a crowded street. Inside, Magnaghi is at work in his bakery, where he makes sweet potato muffins for some of the top hotels in the country, and is trying to develop sweet potato fries for Kenya’s largest chain of coffee shops.

Magnaghi describes himself as a “food application specialist,” but he is an entrepreneur at heart. He has worked in Italy, Australia and Rwanda, but was excited to return home to Kenya to explore the possibilities of sweet potatoes. He says that Kenyan consumers share his excitement, but that he struggles to get enough orange-fleshed sweet potatoes for his many projects. “People are buying it because of the health reasons,” he says. “And then also because it’s a nice orange. It’s bright and it attracts a lot of people.” Yencho tells him that in North Carolina sweet potatoes are being used in beer and that sweet potato syrup is being used as a substitute for honey. “Oh, that I would like to visit,” Magnaghi says.

Several days later, while in Uganda, Yencho sees another success story in a small village outside of Kampala. After driving down a winding, deeply rutted dirt road, Yencho meets Sekiyanja Joweria, who runs the Bagya Basaya (O.F.S.P) Potato Growers and Processors cooperative. The office is a small, plain building with large metal doors and a handful of plastic chairs. Around the back is a single, makeshift greenhouse for growing sweet potato vines. The cooperative, run by 100 women, sells orange-fleshed sweet potato vines to farmers and mills sweet potato flour that can be used to make pancakes, donuts and bread. Joweria does not speak English, so a translator helps as she shares her story.

The cooperative started more than 30 years ago and, initially, grew only white-fleshed sweet potatoes. But after an international health organization found that several children in the village were malnourished, they were convinced to switch to orange-fleshed sweet potatoes in 1998. “We found a lasting solution,” she says. “We started seeing improvement.”

Joweria leads Yencho to a nearby field of sweet potatoes, where they compare notes on growing and harvesting techniques. As is true at farms throughout Uganda, most of the work is done with little more than hands and hoes. The cooperative has been a financial success, enabling the village to pay the school fees for 15 children to go off to college. Joweria’s son graduated with a degree in agriculture and her daughter is studying journalism.

While poverty is evident throughout Africa, Yencho says a closer look reveals opportunities such as those found in a small urban bakery or a rural Ugandan village. “There is real significant poverty here,” he says. “But if you start to peel that away there is an entrepreneurial spirit. There is an emerging middle class and a vibrancy that is really beginning to emerge.”

Nothing Wasted

For all of Covington’s success, there was never one moment when Yencho and Pecota felt it was appropriate to pop the champagne corks. They have a patent on Covington, which is described in the legal documents as an “invention,” and NC State licenses it to be grown in North Carolina and other parts of the country (and even a few other nations). The licensing generates revenue that is used to cover the cost of the university’s breeding program. But in some ways Covington’s success just sort of happened, over time, until it simply became accepted that it was North Carolina’s sweet potato.

But the success is apparent at the farms where it is grown. At Scott Farms in Lucama, N.C., the fifth generation now farms 12,000 acres in five counties. In a gleaming industrial space, computers direct the packing of 40,000–50,000 pounds of sweet potatoes an hour — every week of the year — to ship to U.S. and foreign markets. About 85% of the sweet potatoes are sent to fresh markets, while the remaining 15% is sold to processors — a far cry from the days when some farmers dumped as much as 30% of their crop in the woods because the potatoes were too big or too small or otherwise unfit. “Whatever is in that bin is used for something,” co-owner Dewey Scott told a group of researchers and breeders visiting last year from Africa, South America and elsewhere.

At Vick Family Farms, warehouses can store more than a half million bushels of sweet potatoes and about half of their sweet potatoes are exported to Europe, something that would have been unimaginable two decades ago. “All the stars lined up,” says Jerome Vick. “We have a good variety, good storage conditions, a year-round supply and we could go back after those markets we lost.”

And farmers are finding creative ways to market their sweet potatoes. Yamco, a company in Snow Hill, N.C., distills Covington Gourmet Vodka, which has won top awards competing against vodkas from around the world. Carolina Innovative Food Ingredients, a company in Nashville, N.C., makes sweet potato juice and dehydrated sweet potatoes that can be used in baked goods, beverages and sauces like ketchup and syrup. The Sharps, who grow about 500 acres of sweet potatoes and raise hogs, had the help of NC State food scientists to develop a sausage infused with sweet potato juice, sweet potato puree and chunks of sweet potatoes. It is served, among other places, in Fountain Dining Hall at NC State.

“It’s a better potato now,” Alan Sharp says. “Twenty-five years ago, it wasn’t very good, it was dry and stringy.”

Some even say sweet potatoes are trendy. Kelly McIver, executive director of the N.C. Sweet Potato Commission, notes that sweet potatoes are now found on the menus of high-end restaurants. One of the appetizers served at a wedding reception she attended last year combined sweet potatoes with goat cheese and a pimento. “It’s a sexy food,” she says.

A sexy super food that can rescue a struggling industry and prevent blindness in remote areas of the world? That’s a lot to ask of a simple sweet potato. Even Yencho, ever the optimist, chuckles at the suggestion that the sweet potato could save the world. But its reach is likely to grow, if only because consumers are more conscious about the health benefits of what they eat. Farmers in Uganda and other African countries are going to keep growing sweet potatoes, including those that are orange when you cut them open. And Pecota is not going to stop working on new varieties anytime soon.

The possibilities are endless. And that’s without any tiny, roasted marshmallows.

Article source: NC State

Image: NC State

Banana disease boosted by climate change

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Climate change has raised the risk of a fungal disease that ravages banana crops, new research shows.

Black Sigatoka disease emerged from Asia in the late 20th Century and has recently completed its invasion of banana-growing areas in Latin America and the Caribbean.

The new study, by the University of Exeter, says changes to moisture and temperature conditions have increased the risk of Black Sigatoka by more than 44% in these areas since the 1960s.

International trade and increased banana production have also aided the spread of Black Sigatoka, which can reduce the fruit produced by infected plants by up to 80%.

“Black Sigatoka is caused by a fungus (Pseudocercospora fijiensis) whose lifecycle is strongly determined by weather and microclimate,” said Dr Daniel Bebber, of the University of Exeter.

“This research shows that climate change has made temperatures better for spore germination and growth, and made crop canopies wetter, raising the risk of Black Sigatoka infection in many banana-growing areas of Latin America.

“Despite the overall rise in the risk of Black Sigatoka in the areas we examined, drier conditions in some parts of Mexico and Central America have reduced infection risk.”

The study combined experimental data on Black Sigatoka infections with detailed climate information over the past 60 years.

Black Sigatoka, which is virulent against a wide range of banana plants, was first reported in Honduras in 1972.

It spread throughout the region to reach Brazil in 1998 and the Caribbean islands of Martinique, St Lucia and St Vincent and the Grenadines in the late 2000s.

The disease now occurs as far north as Florida.

“While fungus is likely to have been introduced to Honduras on plants imported from Asia for breeding research, our models indicate that climate change over the past 60 years has exacerbated its impact,” said Dr Bebber.

The Pseudocercospora fijiensis fungus spreads via aerial spores, infecting banana leaves and causing streaked lesions and cell death when fungal toxins are exposed to light.

The study did not attempt to predict the potential effects of future climate on the spread and impact of Black Sigatoka. Other research suggests drying trends could reduce disease risk, but this would also reduce the availability of water for the banana plants themselves.

Read the paper: Philosophical Transactions of the Royal Society B

Article source: University of Exeter

Image: Michel Bertolotti / Pixabay

Wax Helps Plants to Survive in the Desert

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The leaves of date palms can heat up to temperatures around 50 degrees Celsius. They survive thanks to a unique wax mixture that is essential for the existence in the desert.

In 1956, the Würzburg botanist Otto Ludwig Lange observed an unusual phenomenon in the Mauritanian desert in West Africa: he found plants whose leaves could heat up to 56 degrees Celsius. It is astonishing that leaves can withstand such heat. At the time, the professor was unable to say which mechanisms were responsible for preventing the leaves from drying out at these temperatures. More than 50 years later, the botanists Markus Riederer and Amauri Bueno from Julius-Maximilians-Universität Würzburg (JMU) in Bavaria, Germany, succeeded in revealing the secret.

To understand what the two scientists discovered, one must know more about the somewhat complicated structure of a plant leaf. Plant leaves, for example, have a skin that is usually invisible to the human eye. “You can see the skin in the tomato,” explains Professor Riederer, head of the JMU Chair of Botany II. Bioscientists speak of the “cuticle”. It can be imagined as a very thin plastic foil. Without this foil, the leaf of the plant would dry out within a short time: “the water permeability of a cuticle is even lower than that of a plastic foil.”

Constant trade-off: Open or close pores?

The plant skin is not a continuous layer that would extend over the whole leaf. It contains numerous pores, called stomata, which can open and close. The plant “feeds” through these stomata. Riederer: “it thereby uptakes the carbon dioxide the plant needs for photosynthesis.”

The problem is that whenever the pores open to acquire carbon dioxide, water also evaporates. Therefore, desert plants, in particular, are continually undergoing a balancing process: do they uptake carbon dioxide to grow further, or do they close the pores to retain the precious water? According to Riederer, every desert plant decides a little differently.

Colocynths are water-spenders

The plant colocynth (Citrullus colocynthis), also known as bitter cucumber, a wild relative of the watermelon, opens its pores when exposed to heat in order to cool down the leaves by transpiration cooling. It “sweats” so to speak. “This makes colocynth a water-spender,” explains the JMU professor of ecophysiology.

The plant can afford this because it has a very deep root. This enables the plant to tap water sources deep in the desert soil. As Otto Ludwig Lange found out during his experiments in the desert, the colocynth manages to make its leaf up to 15 degrees cooler than the desert air.

Date palms are water-savers

The date palm behaves quite differently. The second Würzburg experimental plant, like the colocynth, lives in oases and wadis – river valleys that dry up over long periods. “In contrast to the colocynth, it is a water-saver,” says Riederer.

Because the palm does not “sweat”, its leaves sometimes reach extremely high temperatures: they can be 11 degrees Celsius above the air temperature. How can it be that the leaves do not dry out at these high temperatures? This is what JMU biologist Amauri Bueno investigated in his doctoral thesis.

High-temperature wax for survival

His results, published in the Journal of Experimental Botany, revolve around the wax, which is embedded in the skin of plants and ensures their low permeability to water. After extensive laboratory tests, Bueno discovered that this wax differs between the colocynth and the date palm.

The date palm has a wax that can withstand high temperatures and therefore has a much more waterproof skin than the colocynth, even at extreme temperatures. Only because of this special wax the palm can survive in the desert. If the wax had a slightly different chemical composition, the leaves would dry very quickly, especially at high temperatures.

According to Riederer, these experiments were highly challenging because the wax embedded in the skin is very complicated from a chemical point of view. Not all secrets have been revealed yet. The bioscientists still do not understand why one plant skin is more permeable for water than the other.

Interesting for plant breeding

These current findings from JMU may be of importance for plant breeding. If one wants to cultivate crop plants in places where is very hot and dry or where climate change could make the surroundings hotter, one has to pay attention to the plant skin when searching for suitable plant varieties. If plants with certain cuticle waxes are selected for breeding, they have a better chance of survival in hot locations.

Read the paper: Journal of Experimental Botany

Article source: Julius-Maximilians-Universität Würzburg (JMU)

Image: Markus Riederer / Universität Würzburg

Tomato, Tomat-oh! Understanding evolution to reduce pesticide use

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Although pesticides are a standard part of crop production, Michigan State University researchers believe pesticide use could be reduced by taking cues from wild plants.

The team recently identified an evolutionary function in wild tomato plants that could be used by modern plant breeders to create pest-resistant tomatoes.

The study, published in Science Advances, traced the evolution of a specific gene that produces a sticky compound in the tips of the trichomes, or hairs, on the Solanum pennellii plant found in the Atacama desert of Peru – one of the harshest environments on earth. These sticky hairs act as natural insect repellants to protect the plant, helping ensure it will survive to reproduce.

“We identified a gene that exists in this wild plant, but not in cultivated tomatoes,” said Rob Last, MSU Barnett Rosenberg Professor of plant biochemistry. “The invertase-like enzyme creates insecticidal compounds not found in the garden-variety tomato. This defensive trait could be bred into modern plants.”

Last explained that modern cultivated tomatoes make fewer of the compounds found in wild plants because – unaware of their adaptive function – breeders removed undesirable traits such as stickiness.

Bryan Leong, plant biology graduate student and co-lead author, is interested in how the wild plants evolved to be insect-resistant.

“We want to make our current tomatoes adapt to stress like this wild tomato, but we can only do that by understanding the traits that make them resistant,” said Leong. “We are using evolution to teach us how to be better breeders and biologists. For example, how can we increase crop yield by creating a pest-resistant plant and eliminate the need to spray fields with insecticides?”

Advances in technology allowed the team to apply genetic and genomic approaches, including the CRISPR gene-editing technology, to the wild tomato plant to discover the functions of specific genes, metabolites and pathways. Using these new techniques, the team identified an invertase-like enzyme specific to the cells at the tips of the sticky hairs. Invertases regulate many aspects of growth and development in plants. In the wild tomato, the enzyme evolved to facilitate the production of new insecticidal compounds.

“It is a race over evolutionary time between the consumed and the consumers,” said Leong. “Insects benefit by eating the plants. Yet, evolution favors plants that make more seeds and pass on their genes to another generation. We hope to take the defensive lessons plants already learned and apply them to existing crops.”

This discovery is a step toward understanding the natural insect resistance of Solanum pennellii plants, which could enable introduction of this trait into cultivated tomatoes using traditional breeding practices.

“Plants are amazing biochemical factories that make many unusual compounds with protective, medicinal and economically important properties,” said Cliff Weil, a program director at the National Science Foundation, which funded this study. “In this study, the authors found that a common enzyme has been repurposed for forming such compounds, giving us important insight into how life is able to bend existing tools for novel uses.”

Read the paper: Science Advances

Article source: Michigan State University

Image: Michigan State University

Risk and unnaturalness cannot justify EU’s strict policy on GMO

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The EU’s policy on GMO is extremely strict and prevents new GMO crops from being authorized. The policy is based on arguments about the risk and unnaturalness of GMO plants – but these arguments cannot justify the restrictive regulation, three researchers conclude in a new study in the journal Transgenic Research. They also conclude that the use of GMO plants is consistent with the principles of organic farming.

The EU’s rules on genetically modified organisms (GMO) are so restrictive that it is virtually impossible to get an authorization for cultivating a GMO crop within the EU—which means that only one GMO crop has hitherto been authorized in the EU. And even if a GMO crop is authorized, individual member states may still ban the crop. This is untenable, argue three researchers from the University of Copenhagen and the Technical University of Denmark in a new article in the scientific journal Transgenic Research, because EU regulation may stand in the way of important agricultural innovation that could provide more sustainable and climate-friendly solutions – and because the strict regulation cannot be justified.

“If we compare the pre-authorization procedure that GMO products undergo with those for conventionally cultivated crops, it is clear that GMO’s are required to meet much stricter demands – with reference to the supposed risks that GMO crops pose. But the fact that a crop has been genetically modified does not in itself pose a risk. If there is risk involved, it is connected to the act of introducing a new variety with unfamiliar traits, which may have adverse effects on the environment or the health of humans and animals,” explains postdoc Andreas Christiansen, who has co-authored the article “Are current EU policies on GMO justified?” with Professor Klemens Kappel and Associate Professor Martin Marchman Andersen.

He continues:

“It is crucial to understand that the introduction of new varieties with compositional differences always poses a risk whether they are genetically modified or not. Our point is that GMO crops should not be treated differently than similar products when the risks they pose to the environment and people are comparable. This is the reason GMO crops have been regulated as other novel varieties in the US for years.”

When is a plant natural?

In a 2010 Eurobarometer survey, 70 per cent of Europeans agreed “that GMO food is fundamentally unnatural”. Unnaturalness is a common argument against GMO crops and foods, and it is mentioned specifically in EU legislation. What the researchers are trying to ascertain is whether the kind of “unnaturalness” which GMO’s supposedly possess can justify bans and restrictive legislation.

“Unnaturalness, firstly, has many different meanings so even though there are cogent arguments that GMO’s in some respects are more unnatural than non-GMO’s, there are also cogent arguments that many GMO’s are just as natural or unnatural as their conventional counterparts,” says Andreas Christiansen.

“One of the arguments is that the more changes human beings have made to a plant, the more unnatural it is. This makes a GMO more unnatural in the sense that it has been subjected to at least one more change than the conventionally bred plant upon which it is based. The conventionally bred plant, conversely, is much more unnatural than its wild ancestor, and has mutated so many times that it may in some cases be difficult to see any relation between to two. It is, in other words, really difficult to construct a solid argument to the effect that the distinction between natural and unnatural can warrant stricter regulation of GMO’s – even if we consider the best philosophical arguments for the value of nature and naturalness” Andreas Christiansen points out.

According to the researchers, many novel gene editing technologies, such as CRISPR/Cas9, are much more precise and cause fewer alterations in plants than traditional breeding methods, in which plant seeds e.g. are washed with chemicals in order to provoke mutations. CRISPR/Cas9 is nonetheless also included in the restrictive EU legislation whereas the chemically induced breeding is not.

GMO produces higher yields than organic farming

Naturalness and organic farming are often thought of as synonymous, and the desire to promote organic farming has been used as an argument for curbing the use of GMO’s, which is prohibited in organic farming. But can a wish to promote organic farming justify a ban on GMO’s?

“Even if we accept that organic farming is superior because it is more sustainable or environmentally friendly, it will be difficult to justify the restrictive policy on GMO, because at least some GMO’s are consistent with these aims of organic farming. And what’s more, current GMO’s are at least as good as conventional farming in terms of sustainability, so it would not make sense to impose stricter regulation on GMO’s than conventional farming as far as sustainability goes,” Andreas Christiansen explains.

“But we must also ask ourselves whether organic farming is always better than the alternatives. In one very important respect, GMO may be superior to organic farming: it can produce higher yields without putting more strain on the environment, which will make it possible to increase food production without increasing the area of land used for farming. This will be extremely important if we are to meet projected future food needs.”

Read the paper: Transgenic Research

Article source: University of Copenhagen

Image: Artverau / Pixabay

Research sheds light on genomic features that make plants good candidates for domestication

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New research published identifies the genomic features that might have made domestication possible for corn and soybeans, two of the world’s most critical crop species.

The research, published in the peer-reviewed academic journal Genome Biology, has implications for how scientists understand domestication, or the process by which humans have been able to breed plants for desirable traits through centuries of cultivation. The researchers drew on vast amounts of data on the genomes of corn and soybeans and compared particular sections of the genomes of wild species and domestic varieties, noting where the genomes diverged most markedly.

Iowa State University researchers worked with scientists from the University of Georgia, Cornell University and the University of Minnesota. The researchers studied more than 100 accessions from comparisons of corn with teosinte, its progenitor species. They also looked at 302 accessions from a dataset of wild and domesticated soybeans.

“We sliced the genomes into specific sections and compared them,” said Jianming Yu, professor of agronomy and Pioneer Distinguished Chair in Maize Breeding. “It’s a fresh angle not many have looked at concerning genome evolution and domestication. We searched for ‘macro-changes,’ or major genome-wide patterns – and we found them.”

Human cultivation created a bottleneck in the genetic material associated with corn and soybeans, Yu said. As humans selected for particular traits they found desirable in their crops, they limited the genetic variation available in the plant’s genome. However, the researchers found several areas in the genomes of the species involved in the study where genome divergence seemed to concentrate.

“These patterns in genome-wide base changes offer insight into how domestication affects the genetics of species,” said Jinyu Wang, the first author of the paper and a graduate student in agronomy.

Variation in nucleotide bases between wild and domesticated species appeared more pronounced in non-genic portions of the genomes, or the parts of the genomes that do not code for proteins. The study also found greater variation in pericentromeric regions, or in areas near the centromere of chromosomes, and in areas of high methylation, or areas in which methyl groups are added to a DNA molecule. Methylation can change the activity of a DNA segment without changing its sequence.

The study looked at the occurrence of mutations in the genomes of the domesticated crops and their progenitor species.

“We now think it’s likely that good candidates for domestication, such as corn and soybeans, occupy a middle ground in their willingness to mutate,” said Xianran Li, adjunct associate professor of agronomy and a co-corresponding author of the study.

“If there’s no mutation, then everything stays the same and we don’t have evolution,” Yu said. “But too many mutations can wipe out a species.”

The study’s findings pointed to important links between UV radiation from the sun and genome evolution. UV radiation is a natural mutagen, and it leaves a special footprint when it occurs, Yu said. The study’s authors found many more of these footprints in modern corn and soybeans than their wild relatives.

Read the paper: Genome Biology

Article source: Iowa State University

Image: Sherry Flint-Garcia (teosinte) and Scott Jackson (Glycine soja)

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