As their Latin name indicates, pineapples are truly “excellent fruits”—and thanks to a freshly completed genome sequencing project, researchers have gained a new understanding of how human agriculture has shaped the evolution of this and other crops.
Scientists have discovered that soil microbes can make tomato plants more resistant to Bacterial wilt disease caused by Ralstonia solanacearum— opening new possibilities for sustainable food production.
Almond and the peach are two well-known tree species, since humans have been eating their fruit (peach) or seed (almond) for thousands of years. New research shows that the movement of the transposons could lie at the origin of the differences between the fruit of both species or the flavour of the almond.
World leaders gather for the UN General Assembly on the 25th September, hundreds of emerging leaders focused on fighting global inequality came together at the Bill & Melinda Gates Foundation’s third annual Goalkeepers event in New York City. Among them, University of Illinois scientist Amanda De Souza highlighted a crop of inequality called cassava, which has starchy, tuberous roots that sustain more than 500 million people in sub-Saharan Africa, yet cassava has been largely neglected by research and development compared to the staple crops of wealthier regions. Recently, De Souza and a team from Realizing Increased Photosynthetic Efficiency (RIPE) published a study in New Phytologist that identified opportunities to improve cassava yields—which have not increased for more than fifty years in Africa.
“For smallholder farmers who depend on tiny plots of land to feed and support their families, cassava is a ‘backup’ crop when other crops fail,” De Souza said at Goalkeepers, where she described her work to improve cassava through the RIPE project. “Especially for women, who represent a majority of smallholder farmers, cassava is a savings account. It is a resource they can harvest all year to pay for things like medical treatments and their children’s school fees.”
The RIPE project is an international effort to develop more productive crops by improving photosynthesis—the natural, sunlight-powered process that all plants use to fix carbon dioxide into carbohydrates that fuel growth, development, and ultimately yields.
Led by RIPE researchers at Illinois and Lancaster University, this study examined factors that limit photosynthesis in 11 popular, or farmer-preferred, African varieties of cassava with the goal to eventually help cassava overcome photosynthetic limitations to boost yields.
First, the team examined the photosynthetic limitations of cassava exposed to constant high levels of light, like a plant would experience at midday with cloudless skies. In these conditions, and like many crops, cassava’s photosynthesis is limited (by as much as 80 percent) by two factors: One half is due to the low speed that carbon dioxide molecules travel through the leaf to reach the enzyme that drives photosynthesis, called Rubisco. The other half is because Rubisco sometimes fixes oxygen molecules by mistake, wasting large amounts of the plant’s energy.
Next, the team evaluated the limitations of photosynthesis under fluctuating light conditions. Surprisingly, and unlike most crops, Rubisco was not the primary limiting factor when leaves transitioned from shade to sunlight, like when the sun comes out from behind a cloud. Instead, cassava is limited by stomata, which are microscopic pores on the surface of leaves that open to allow carbon dioxide to enter the plant but at the cost of water that escapes through these same pores. Stomata are partially closed in the shade and open in response to light when Rubisco is active.
“Rubisco is the major limiting factor during this transition from shade to light for most plants, including rice, wheat, and soybean,” De Souza said. “Cassava is the first crop that we have found where stomata limit photosynthesis during these light transitions more than Rubisco.”
Illinois’ Postdoctoral Researcher Yu Wang created a computer model to quantify how much cassava would gain by overcoming this limitation. According to the leaf-level model, if stomata could open three times faster, cassava could fix 6 percent more carbon dioxide each day. In addition, cassava’s water use efficiency—the ratio of biomass produced to water lost by the plant—could be improved by 16 percent.
In addition, the team found that it takes as long as 20 minutes for cassava to transition from shade to full light and reach the maximum rate of photosynthesis, which is quite slow compared to other crops such as rice that can transition in just a few minutes. However, the fastest variety of cassava could transition almost three times faster and fix 65 percent more carbon dioxide into carbohydrates than the slowest variety. Closing this gap is another opportunity to improve cassava’s productivity.
“Plants are constantly moving from shade to light as leaves shift and clouds pass overhead,” said RIPE Director Stephen Long, Ikenberry Endowed University Chair of Crop Sciences and Plant Biology at Illinois’ Carl R. Woese Institute for Genomic Biology, who contributed to this study. “We hope that the variation that we discovered during these light transitions among cassava varieties can be used to identify new traits, and therefore opportunities for us to improve cassava’s photosynthetic efficiency and yield potential.”
2019 marks the third year of Goalkeepers, an initiative dedicated to accelerating progress towards the Global Goals. The Goalkeepers annual event in New York is a gathering of approximately 400 world leaders, global activists, and community changemakers, using powerful stories, data and partnerships to highlight progress achieved, hold governments accountable and bring together a new generation of leaders to address the world’s major challenges.
Read the paper: New Phytologist
Article source: Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign
As a growing population and climate change threaten food security, researchers around the world are working to overcome the challenges that threaten the dietary needs of humans and livestock. A pair of scientists is now making the case that the knowledge and tools exist to facilitate the next agricultural revolution we so desperately need.
In order to meet the demands of growing human populations, agricultural production must double within the next 30 years. Yet the health of today’s crops and the promise of their yield face a rising slate of threats—from pests to chaotic weather events—leading to an urgent need to identify effective, natural plant defense strategies.
An international team succeeded in assembling the first sequence of the pea genome. This study will, in addition to increasing knowledge of this genome compared to that of other legumes, help to improve traits of interest for peas, such as disease resistance, regularity of yield and nutritional value.
Climate change could negatively impact banana cultivation in some of the world’s most important producing and exporting countries, a study has revealed.
Citrus fruits, coffee and avocados: The food on our tables has become more diverse in recent decades. However, global agriculture does not reflect this trend. Monocultures are increasing worldwide, taking up more land than ever. At the same time, many of the crops being grown rely on pollination by insects and other animals. This puts food security at increased risk, as a team of researchers writes in the journal “Global Change Biology“. For the study, the scientists examined global developments in agriculture over the past 50 years.
The researchers analysed data from the United Nations’ Food and Agriculture Organization (FAO) on the cultivation of field crops between 1961 and 2016. Their evaluation has shown that not only is more and more land being used for agriculture worldwide, the diversity of the crops being grown has declined. Meanwhile, 16 of the 20 fastest growing crops require pollination by insects or other animals. “Just a few months ago, the World Biodiversity Council IPBES revealed to the world that up to one million animal and plant species are being threatened with extinction, including many pollinators,” says Professor Robert Paxton, a biologist at MLU and one of the authors of the new study. This particularly affects bees: honeybees are increasingly under threat by pathogens and pesticides, and populations of wild bees have been on the decline around the world for decades.
Fewer pollinators could mean that yields are much lower or even that harvests fail completely. However, risks are not spread equally across the world. The researchers used the FAO data to create a map showing the geographical risk of crop failure. “Emerging and developing countries in South America, Africa and Asia are most affected,” says Professor Marcelo Aizen of the National Council for Scientific and Technological Research CONICET in Argentina, who led the study. This is not surprising, he says, since it is precisely in these regions where vast monocultures are grown for the global market. Soy is produced in many South American countries and then exported to Europe as cattle feed. “Soy production has risen by around 30 percent per decade globally. This is problematic because numerous natural and semi-natural habitats, including tropical and subtropical forests and meadows, have been destroyed for soy fields,” explains Aizen.
According to the authors, current developments have little to do with sustainable agriculture, which focuses on the food security of a growing world population. And, although poorer regions of the world are at the greatest risk, the consequences of crop failure would be felt worldwide: “The affected regions primarily produce crops for the rich industrial nations. If, for example, the avocado harvest in South America fails, people in Germany and other industrial nations may no longer be able to buy them,” concludes Robert Paxton, who is also a member of the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig.
The researchers advocate for a trend reversal: Care should be taken to diversify agriculture worldwide and make it more ecological. This means, for example, that farms in particularly susceptible countries should grow a diversity of crops. In addition, farmers all over the world would need to make the areas under cultivation more natural, for example by planting strips of flowers or hedgerows next to their fields and by providing nesting habitats on field margins. This would ensure that there are adequate habitats for insects, which are essential for sustainable and productive farming.
Read the paper: Global Change Biology
Article source: Martin-Luther-Universität Halle-Wittenberg
Image: Martin Husemann
A team of Clemson University scientists has achieved a breakthrough in the genetics of senescence in cereal crops with the potential to dramatically impact the future of food security in the era of climate change.
The collaborative research, which explores the genetic architecture of the little understood process of senescence in maize (a.k.a. corn) and other cereal crops, was published in The Plant Cell, one of the top peer-reviewed scientific journals of plant sciences. Rajan Sekhon, a plant geneticist and an assistant professor in the College of Science’s department of genetics and biochemistry, is the lead and corresponding author of the paper titled “Integrated Genome-Scale Analysis Identifies Novel Genes and Networks Underlying Senescence in Maize.”
“Senescence means ‘death of a cell or an organ in the hands of the very organisms it is a part of,’ ” Sekhon said. “It happens pretty much everywhere, even in animals. We kill the cells we don’t need. When the weather changes in fall, we have those nice fall colors in trees. At the onset of fall, when the plants realize that they cannot sustain the leaves, they kill their leaves. It is all about the economy of energy.”
As a result, the leaves die off after their show of color. The energy scavenged from the leaves is stored in the trunk or roots of the plant and used to quickly reproduce leaves next spring. This makes perfect sense for trees. But the story is quite different for some other edible plants, specifically cereal crops like maize, rice and wheat.
“These crops are tended very carefully and supplied excess nutrients in the form of fertilizers by the farmers,” Sekhon said. “Instead of dying prematurely, the leaves can keep on making food via photosynthesis. Understanding the triggers for senescence in crops like maize means scientists can alter the plant in a way that can benefit a hungry world.”
Sekhon, whose research career spans molecular genetics, genomics, epigenetics and plant breeding, established his lab in 2014 as an assistant professor. He has played a key role in the development of a “gene atlas” widely used by the maize research community. He has published several papers in top peer-reviewed journals investigating the regulation of complex plant traits.
“If we can slow senescence down, this can allow the plant to stay green – or not senesce – for a longer period of time,” Sekhon said. “Plant breeders have been selecting for plants that senesce late without fully understanding how senescence works at the molecular level.”
These plants, called “stay-green,” live up to their name. They stay green longer, produce greater yields and are more resilient in the face of environmental factors that stress plants, including drought and heat.
But even with the existence of stay-green plants, there has been little understanding about the molecular, physiological and biochemical underpinnings of senescence. Senescence is a complex trait affected by several internal and external factors and regulated by a number of genes working together. Therefore, off-the-shelf genetic approaches are not effective in fully unraveling this enigmatic process. The breakthrough by Sekhon and his colleagues was the result of a systems genetics approach.
Sekhon and the other researchers studied natural genetic variation for the stay-green trait in maize. The process involved growing 400 different maize types, each genetically distinct from each other based on the DNA fingerprint (i.e., genotype), and then measuring their senescence (i.e., phenotype). The team then associated the “genotype” of each inbred line with its “phenotype” to identify 64 candidate genes that could be orchestrating senescence.
“The other part of the experiment was to take a stay-green plant and a non-stay-green plant and look at the expression of about 40,000 genes during senescence,” Sekhon said. “Our researchers looked at samples every few days and asked which genes were gaining expression during the particular time period. This identified over 600 genes that appear to determine whether a plant will be stay-green or not.
“One of the big issues with each of these approaches is the occurrence of false positives, which means some of the detected genes are flukes, and instances of false negatives, which means that we miss out on some of the causal genes.”
Therefore, Sekhon and his colleagues had to painstakingly combine the results from the two large experiments using a “steams genetics” approach to identify some high-confidence target genes that can be further tested to confirm their role in senescence. They combined datasets to narrow the field to 14 candidate genes and, ultimately, examined two genes in detail.
“One of the most remarkable discoveries was that sugars appear to dictate senescence,” Sekhon said. “When the sugars are not moved away from the leaves where these are being made via photosynthesis, these sugar molecules start sending signals to initiate senescence.”
However, not all forms of sugar found in the plants are capable of signaling. One of the genes that Sekhon and colleagues discovered in the study appears to break complex sugars in the leaf cells into smaller sugar molecules – six-carbon sugars like glucose and fructose – that are capable of relaying the senescence signals.
“This is a double whammy,” Sekhon said. “We are not only losing these extra sugars made by plants that can feed more hungry mouths. These unused sugars in the leaves start senescence and stop the sugars synthesis process all together.”
The implications are enormous for food security. The sugars made by these plants should be diverted to various plant organs that can be used for food.
“We found that the plant is carefully monitoring the filling of the seeds. That partitioning of sugar is a key factor in senescence. What we found is there is a lot of genetic variation even in the maize cultivars that are grown in the U.S.”
Some plants fill seeds and then can start filling other parts of the plant.
“At least some of the stay-green plants are able to do this by storing extra energy in the stems,” Sekhon said. “When the seed is harvested, whatever is left in the field is called stover.”
Stover can be used as animal feed or as a source of biofuels. With food and energy demand increasing, there is a growing interest in developing dual-purpose crops which provide both grain and stover. As farmland becomes scarce, plants that senesce later rise in importance because they produce more overall energy per plant.
The genes identified in this study are likely performing the same function in other cereal crops, such as rice, wheat and sorghum. Sekhon said that the next step is to examine the function of these genes using mutants and transgenics.
“The ultimate goal is to help the planet and feed the growing world. With ever-worsening climate, shrinking land and water, and increasing population, food security is the major challenge faced by mankind,” Sekhon said.
In addition to Sekhon, other contributors include Rohit Kumar, Christopher Saski, Arlyn Ackerman, William Bridges, Barry Flinn and Feng Luo of Clemson University; Timothy Beissinger of the University of Gottingen; and Matthew Breitzman, Natalia de Leon and Shawn Kaeppler of the University of Wisconsin-Madison.
Read the paper: The Plant Cell
Article source: Clemson University
Image: Clemson University/College of Science