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University of Adelaide researchers have discovered a biochemical mechanism fundamental to plant life that could have far-reaching implications for the multibillion dollar biomedical, pharmaceutical, chemical and biotechnology industries.

There are up to 80,000 fundamental-to-life enzymes working in plant or mammalian bodies, upon which almost all biochemical reactions depend. Enzymes carry out many chemical reactions, products of which can be used as building blocks or metabolites in a body, or they can serve as an energy source for every function in a body.

Researchers have discovered a new enzyme catalytic mechanism – catalysis being a process which speeds up chemical reactions – which they say could impact on work in biofuels production, in food and materials processing, and in drug discovery.

Their work has been published today in Nature Communication.

“The foundation for this was laid down in our earlier work but, at that time, we could not explain some fundamental processes at work in plants as these occur at immense rates,” said lead researcher Professor Maria Hrmova from the University of Adelaide’s School of Agriculture, Food and Wine.

“The solution to this came up only recently, when we combined high-resolution X-ray crystallography, enzyme kinetics, mass spectrometry, nuclear magnetic resonance spectroscopy, and multi-scale 3D molecular modelling tools to show those super-fast processes.

“Using computer simulations, we discovered a remarkable phenomenon during initial and final catalytic events near the surface of the plant glucose-processing enzyme. The enzyme formed a cavity which allowed the trapped glucose to escape to allow for the next round of catalysis,” Professor Hrmova said.

“Now that we can simulate these nanoscale movements we have opened the door to new knowledge on enzyme dynamics that was inaccessible before. These discoveries are made once in a generation.”

Professor Hrmova said the discovery of the catalytic mechanism involved specialists in plant and molecular biology, biochemistry, biophysics, bioinformatics and computer science from seven countries (Australia, France, Thailand, Spain, Chile, Slovak Republic and China).

“Being able to describe these minute and ultra-fast processes – unable to be captured via usual experimental techniques – means we can now work to improve enzyme catalytic rates, stability and product inhibition. This will have significance in biotechnologies to develop or manufacture products through novel forms of bioengineered enzymes that could be also used outside of biological systems.”

A movie describing the discovered catalytic mechanism can be seen here.

Read the paper: Nature Communication

Article source: University of Adelaide

Image: Designed by macrovector / Freepik

Cotton breeders face a “Catch-22.” Yield from cotton crops is inversely related to fiber quality. In general, as yield improves, fiber quality decreases, and vice-versa. “This is one of the most significant challenges for cotton breeders,” says Peng Chee, a researcher at the University of Georgia.

To overcome the yield vs quality challenge, Chee and colleagues turned to obsolete cultivars – or strains – of cotton with ‘exotic’ genetic material. In a new study, they report findings that could help breeders improve cotton fiber quality while maintaining or even improving yield.

The study focused on the genetics of hybrid ‘Sealand’ cultivars. These cultivars were developed by breeding two different species of cotton – Upland and Sea Island. Sea Island cotton is the type generally also known as “Pima or Egyptian cotton” from the species Gossypium barbadense. Its fibers are found in the highest quality garments and linens, due to its long, strong and fine fibers.

About 97% of the cotton grown in the United States is Upland cotton from the species Gossypium hirsutum. Upland cotton has much higher yields and broader adaptation, but lower fiber quality compared to Pima cotton. “The breeding challenge lies in transferring Pima fiber quality to Upland,” says Chee.

Because they are two different species, there are significant genetic barriers between Upland and Pima. These differences can cause genetic abnormalities during and after breeding. Starting in the 1930s and 40s, breeders at the USDA successfully bred Upland with Sea Island cotton species. The results of these breeding efforts were the Sealand cotton cultivars, which has the appearance of Upland but with much improved fiber quality. In fact, a couple of Sealand cultivars were commercially grown briefly in parts of the US in the 1950s. “However, the genetic details of Sealand cultivars have remained largely unknown,” says Chee.

Until now. Chee and colleagues generated genetic ‘maps’ of two Sealand cultivars. They found that the superior fiber quality of Sealand cotton were in part due to genes inherited from the Sea Island cotton. Fiber length, for example, is one aspect of cotton fiber quality. The researchers found that two of the three genetic segments controlling fiber length in one of the Sealand cultivars was inherited from the Sea Island parent.

“These detailed genetic dissections help us better understand interspecies hybridization,” says Chee. “Now that we know which part of the genome controls fiber quality, we can now develop tools to select for these traits. We can also select desirable combinations of genes to improve multiple fiber quality traits.”

Improving cotton quality can have ramifications for international trade. The global cotton import-export market is estimated to be worth more than 12 billion dollars. The United States is the largest exporter of cotton.

In addition to improving fiber quality, there may be other benefits to combining Pima and Upland genetics. “Upland cotton has been domesticated from a very small set of wild relatives,” says Chee. “Selection for specific traits in the distant past led to the loss of other potentially useful traits.”

To address the issue of low genetic diversity, breeders turn to wild relatives or ‘cousins”, such as Pima. They search for useful genes influencing important traits, such fiber quality. They also look for genes connected to other traits, including drought tolerance and disease resistance.

Genetic segments from Pima cotton that have positive effects on fiber quality have been tagged with molecular markers. These markers make it easier for breeders to track genetic segments through generations. Cotton breeders can now use these genetic tools to guide their efforts in breeding new cultivars. For example, they can focus on the portions of the genome that improve fiber quality while maintaining or even increasing yields.

The researchers are testing a small subset of the Pima genetic segments they discovered in the study in different genetic backgrounds. “We want to confirm their desirable effects across a more diverse set of varieties,” says Chee. “Then they will be more useful in cotton breeding programs across the cotton belt.”

Read the paper: Crop Science

Article source: American Society of Agronomy

Image: Peng Chee

Recent flooding in the Midwest has brought attention to the complex agricultural problems associated with too much rain. Data from the past three decades suggest that excessive rainfall can affect crop yield as much as excessive heat and drought. In a new study, an interdisciplinary team from the University of Illinois linked crop insurance, climate, soil and corn yield data from 1981 through 2016.

The study found that during some years, excessive rainfall reduced U.S. corn yield by as much as 34% relative to the expected yield. Data suggest that drought and excessive heat caused a yield loss of up to 37% during some years. The findings are published in the journal Global Change Biology.

“We linked county-level U.S. Department of Agriculture insurance data for corn loss with historical weather data, letting us quantify the impact of excessive rainfall on yield loss at a continental scale,” said Kaiyu Guan, a natural resources and environmental sciences professor and the study’s principal investigator. “This was done using crop insurance indemnity data paired with rigorous statistical analysis – not modeled simulations – which let the numbers speak for themselves.”

The study found that the impact of excessive rainfall varies regionally.

“Heavy rainfall can decrease corn yield more in cooler areas and the effect is exacerbated even further in areas that have poor drainage,” said Yan Li, a former University of Illinois postdoctoral researcher and lead author of the study.

Excessive rainfall can affect crop productivity in various ways, including direct physical damage, delayed planting and harvesting, restricted root growth, oxygen deficiency and nutrient loss, the researchers said.

“It is challenging to simulate the effects of excessive rainfall because of the vast amount of seemingly minor details,” Li said. “It is difficult to create a model based on the processes that occur after heavy rainfall – poor drainage due to small surface features, water table depth and various soil properties can lead to ponding of water in a crop field. Even though the ponding may take place over a small area, it could have a large effect on crop damage.”

“This study shows that we have a lot of work to do to improve our models,” said Evan DeLucia, the director of the Institute for Sustainability, Energy and Environment, a professor of integrative biology and study co-author. “While drought and heat stress have been well dealt with in the existing models, excessive rainfall impacts on crop system are much less mature.”

Many climate change models predict that the U.S. Corn Belt region will continue to experience more intense rainfall events in the spring. Because of this, the researchers feel that it is urgent for the government and farmers to design better risk management plans to deal with the predicted climate scenarios.

“As rainfall becomes more extreme, crop insurance needs to evolve to better meet planting challenges faced by farmers,” said Gary Schnitkey, a professor of agricultural and consumer economics and study co-author.

Read the paper: Global Change Biology

Article source: University of Illinois

Image: L. Brian Stauffer

A collaborative team led by Prof. BAI Yang and Prof. CHU Chengcai from the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (CAS), recently examined the variation in root microbiota within 68 indica and 27 japonica rice varieties grown in field conditions. They revealed that the indica and japonica varieties recruited distinct root microbiota.

In natural soil, plant roots provide an ecological niche for multiple soil microorganisms known as root microbiota. These microbes develop an intimate association with plants, enhancing plants’ nutrient uptake, growth and tolerance to pathogens.

Indica and japonica are the two major subspecies of cultivated rice (Oryza sativa L.). Indica varieties show better nitrogen use efficiency (NUE) compared with japonica varieties in the field; NRT1.1B contributes to this natural variation in rice. However, the effect of root microbiota on the NUE variation observed between the indica and japonica varieties is not yet clear.

The researchers established a model using a random-forest machine-learning approach. They found this model could accurately predict indica and japonica varieties in tested fields, suggesting that the root microbes can serve as a biomarker to distinguish indica and japonica varieties.

It is interesting that indica varieties had more bacteria associated with the function of nitrogen metabolism compared with japonica varieties, indicating that nitrogen transformation is more active in the root environment of indica rather than japonica varieties.

By comparing root-associated microbiota of wild-type varieties and the the nrt1.1b mutant, they found that NRT1.1B was associated with the recruitment of approximately half of the indica-enriched bacterial taxa.

Notably, wild-type varieties showed relative abundance of root bacteria that harbor key genes for the ammonification process; however, there was no such abundance in the root microbiome of the nrt1.1b mutant. This indicates that such root microbes may catalyze the formation of ammonium in the root environment.

Using an improved high-throughput protocol to cultivate and identify bacteria, the researchers successfully cultivated more than 70 percent of the bacterial species that were reproducibly detectable in the rice roots, and established the first systematic collection of rice root bacterial cultures.

They then used gnotobiotic experimental systems with a reconstructed synthetic community (SynCom) and found that indica-enriched SynCom showed a stronger ability to promote rice growth under a supply of organic nitrogen than japonica-enriched SynCom. This further suggests that indica-enriched bacteria may contribute to higher nitrogen-use efficiency in indica rice.

These results not only reveal the relationship between the root microbiome and NUE in rice subspecies, but demonstrate the role of NRT1.1B in the establishment of root microbiota. The bacterial culture collections provide a resource for functional research of root microbiota.

The research on the interaction between root microbes and rice has laid an important foundation for the application of beneficial microbes to the process of nitrogen utilization and provides a theoretical basis for reducing nitrogen fertilizer in sustainable agriculture.

Read the paper: Nature Biotechnology

Article source: Chinese Academy of Sciences (CAS)

Image: Trung Hieu Dang / Pixabay

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

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 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

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

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

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