New genetic analysis advances the global quest for yellow rust resistant wheat

A wheat leaf infected with yellow rust, also known as stripe rust. Photo: Thomas Lumpkin/CIMMYT

Yellow rust, also known as stripe rust, is a tenacious and widespread fungal disease that threatens wheat all over the world. The fungal pathogen that causes the rust — Puccinia striiformis — is prevalent in more than 60 countries, and an estimated 88% of the world’s wheat production is considered vulnerable, with up to 100% losses. 

A number of factors – including favorable weather conditions, the adaptation of existing races and emergence of new ones, and a changing climate – have caused a recent uptick in severe outbreaks. Farmers can use fungicides and farming management practices to battle the fungus, but sowing resistant seeds is widely considered as the most cost-effective, environmentally-safe and sustainable way to beat it.

A new analysis by wheat scientists at the International Maize and Wheat Improvement Center (CIMMYT) published in Scientific Reports provides valuable insights and a deep resource of genetic information to increase the speed and accuracy of efforts to breed yellow rust resistant wheat.

To understand the shared genetic basis of yellow rust resistance over time and in three geographic regions, CIMMYT scientists performed a large genome-wide association study leveraging a dataset of 43,706 observations on 23,346 wheat lines evaluated between 2013 and 2019 at sites in India, Kenya and Mexico.

Photo: Flickr/ Wheat Genetics Lab

They found more than 100 repeatable –that is, statistically significant in multiple datasets — genome-wide markers associated with yellow rust that aligned to the reference genome of wheat.

 “These findings represent a significant advancement in our knowledge about the genetics of yellow rust resistance in bread wheat and provide exciting opportunities for designing future genomics-based breeding strategies for tackling yellow rust,” said CIMMYT wheat scientist Philomin Juliana, the lead author of the paper.

CIMMYT wheat scientists have been breeding for yellow rust resistance since the early 1970s. Breeding for resistance is a painstaking process involving crossing parents with slow rusting genes, selecting early-generation plants which exhibit resistance in Toluca, Mexico, and then subjecting the advanced generations to intense screening in sites like Karnal (in collaboration with the Indian Institute of Wheat and Barley Research) and Ludhiana (in collaboration with the Borlaug Institute for South Asia) in India; Njoro in Kenya; and Celaya (in collaboration with the Instituto Nacional de Investigaciones Forestales, Agricolas y Pecuarias), El Batan and Toluca in Mexico. Identifying genes related to resistance can increase the efficiency of this selection process, giving breeders a head start by allowing them to begin the crossing process with varieties that are more likely to have resistance genes.

In the study, the wheat scientists also conducted “allelic fingerprinting” on the largest panel of wheat breeding lines to date — 52,067 lines, genomically characterizing them for yellow rust resistance.  The resulting data creates opportunities using molecular markers to identify varieties with desired combinations of resistance genes.

“This information advances our knowledge on the genetics of yellow rust resistance in thousands of wheat lines, and has important implications for the future design of resistant crosses and varieties,” Juliana said.

Overall, the markers and fingerprints identified in this study are a valuable resource not only for CIMMYT breeders but also for the global wheat breeding community in its efforts to accelerate yellow rust resistance breeding.

This work was made possible by the generous support of the Delivering Genetic Gain in Wheat (DGGW) project funded by the Bill & Melinda Gates Foundation and the UK  Department for International Development (DFID) and managed by Cornell University; the U.S. Agency for International Development’s Feed the Future Initiative; and the genotyping support of Dr. Jesse Poland from the innovation lab at Kansas State University.

Read the full article here:
https://doi.org/10.1038/s41598-020-67874-x

Juliana, P., Singh, R.P., Huerta-Espino, J. et al. 2020. “Genome-wide mapping and allelic fingerprinting provide insights into the genetics of resistance to wheat stripe rust in India, Kenya and Mexico.” Nature Scientific Reports.

MARPLE: the real-time cereal killer detective

Photo: Matt Heaton/JIC

A new case study by the Biotechnology and Biological Sciences Research Council shines a spotlight on the MARPLE (Mobile and Real-time PLant disEase) Diagnostics kit, a revolutionary technology that can identify fungus strains in just two days.

MARPLE, which was developed by the John Innes Centre in collaboration with the International Maize and Wheat Improvement Center (CIMMYT) and the Ethiopian Institute of Agricultural Research (EIAR), is currently being rolled out across five major research hubs in Ethiopia. As sub-Saharan Africa’s largest wheat producer, Ethiopia is considered “a gateway for new rust pathogen strains entering from Asia”.

Read the case study:

MARPLE: the real-time cereal killer detective

Preserving the legacy of biodiversity

This story by Alfonso CortésRodrigo Ordóñez and Silvia Rico was originally published on the CIMMYT website.

A NordGen staff member brings a box of seed into the Global Seed Vault in Svalbard, Norway. (Photo: Thomas Sonne/Common Ground Media for NordGen)

Seed security is the first step towards food security. The International Maize and Wheat Improvement Center (CIMMYT) preserves 28,000 unique seed samples of maize and 150,000 of wheat at its genebank in Mexico.

The Global Seed Vault in Svalbard opened in 2008. Since then, CIMMYT has duplicated and deposited 50 million seeds — 170,000 samples of maize and wheat — at Svalbard.

This year, CIMMYT sent 24 boxes of seed, with 332 samples of maize and 15,231 samples of wheat.

Join these seeds on a journey, as they travel more than 8,000 km from CIMMYT’s genebank in Mexico to the Global Seed Vault in the Arctic.

A supermarket, rather than a museum

This treasure, kept in the global network of genebanks, is key to ensuring sustainable, nutritious agricultural systems for future generations.

The purpose of genebanks is not just to preserve seed, but to use its biodiversity to address the needs of the future — and the needs of today.

Climate change is already impacting resource-poor farmers and consumers in low- and middle-income countries. Researchers and breeders at CIMMYT are rolling out solutions to these challenges, based on the diverse genetic resources kept in the genebank. As a result, farmers can use new varieties that yield more, need less inputs, and are more tolerant to drought or heat.

Our internal estimates show that about 30% of maize and more than 50% of wheat grown worldwide can be traced to CIMMYT germplasm.

Humanity’s legacy

Maize and wheat originated about 10,000 years ago. Since then, it’s survived war, drought, diseases, migration, birds, low yields — and the hard choice between feeding children or planting again.

Keepers of genebanks around the world are only the depositors of this legacy, which belongs to all humanity. CIMMYT will continue to preserve these seeds and to make their biodiversity available to researchers and famers, to solve today’s and tomorrow’s most pressing issues.

An environmental look at WHEAT research

As we recognize the 50th year of Earth Day, the CGIAR Research Program on Wheat (WHEAT) looks back on recent impactful research to increase crop productivity while conserving natural resources.

WHEAT and its lead research partner, the International Maize and Wheat Improvement Center (CIMMYT), are proud of our research to move the needle on improving the environmental sustainability of farming and food production.

Plant resistance to insects

The 24th biannual session of the International Plant Resistance to Insects (IPRI) workshop, held at CIMMYT headquarters this year, featured innovative insect resistance solutions to the global threat of crop pests. Their goal: to reduce the use of pesticides.

Conservation agriculture

WHEAT and CIMMYT research has consistently shown the wide-ranging benefits of conservation agriculture practices such as zero tillage, crop rotation and soil cover – for crop performance, water use efficiency, farmer incomes and climate action. This research helps governments in South Asia — a global “hotspot” for climate vulnerability – develop policies to prioritize and encourage these techniques.

Appropriate fertilizer use

Research by WHEAT scientist Tek Sapkota has identified the optimum rates of nitrogen fertilizer application for rice and wheat in the Indo-Gangetic Plains of India — minimizing dangerous greenhouse gas emissions while maintaining crop productivity.

Reducing residue burning

A  study  by a global team including WHEAT scientist ML Jat shows that replacing rice residue burning with no-till farming practices raises farmers’ profits, cuts farm-related greenhouse gas emissions by as much as 78%, and lowers the choking air pollution that plagues the region each winter. These findings support Indian government policies including a US$166 million subsidy to promote mechanization such as the Happy Seeder.

Earth Day 1970 gave a voice to an emerging public consciousness about the state of our planet. With the same consciousness, we at WHEAT continue to work on research solutions to sustainably increase the production of nutritious wheat for improved livelihoods throughout the world.

Blast and rust forecast

This story by Matthew O’ Leary was originally published on the CIMMYT website.

An early warning system set to deliver wheat disease predictions directly to farmers’ phones is being piloted in Bangladesh and Nepal by interdisciplinary researchers.

Experts in crop disease, meteorology and computer science are crunching data from multiple countries to formulate models that anticipate the spread of the wheat rust and blast diseases in order to warn farmers of likely outbreaks, providing time for pre-emptive measures, said Dave Hodson, a principal scientist with the International Maize and Wheat Improvement Center (CIMMYT) coordinating the pilot project.

Around 50,000 smallholder farmers are expected to receive improved disease warnings and appropriate management advisories through the one-year proof-of-concept project, as part of the UK Aid-funded Asia Regional Resilience to a Changing Climate (ARRCC) program.

Early action is critical to prevent crop diseases becoming endemic. The speed at which wind-dispersed fungal wheat diseases are spreading through Asia poses a constant threat to sustainable wheat production of the 130 million tons produced in the region each year.

“Wheat rust and blast are caused by fungal pathogens, and like many fungi, they spread from plant to plant — and field to field — in tiny particles called spores,” said Hodson. “Disease strain mutations can overcome resistant varieties, leaving farmers few choices but to rely on expensive and environmentally-damaging fungicides to prevent crop loss.”

“The early warning system combines climate data and epidemiology models to predict how spores will spread through the air and identifies environmental conditions where healthy crops are at risk of infection. This allows for more targeted and optimal use of fungicides.”

The system was first developed in Ethiopia. It uses weather information from the Met Office, the UK’s national meteorological service, along with field and mobile phone surveillance data and disease spread modeling from the University of Cambridge, to construct and deploy a near real-time early warning system.

Initial efforts focused on adapting the wheat stripe and stem rust model from Ethiopia to Bangladesh and Nepal have been successful, with field surveillance data appearing to align with the weather-driven disease early warnings, but further analysis is ongoing, said Hodson.

“In the current wheat season we are in the process of comparing our disease forecasting models with on-the-ground survey results in both countries,” the wheat expert said.

“Next season, after getting validation from national partners, we will pilot getting our predictions to farmers through text-based messaging systems.”

CIMMYT’s strong partnerships with governmental extension systems and farmer associations across South Asia are being utilized to develop efficient pathways to get disease predictions to farmers, said Tim Krupnik, a CIMMYT Senior Scientist based in Bangladesh.

“Partnerships are essential. Working with our colleagues, we can validate and test the deployment of model-derived advisories in real-world extension settings,” Krupnik said. “The forecasting and early warning systems are designed to reduce unnecessary fungicide use, advising it only in the case where outbreaks are expected.”

Local partners are also key for data collection to support and develop future epidemiological modelling, the development of advisory graphics and the dissemination of information, he explained.

The second stage of the project concerns the adaptation of the framework and protocols for wheat blast disease to improve existing wheat blast early warning systems already pioneered in Bangladesh.

Strong scientific partnership champions diversity to achieve common goals

The meteorological-driven wheat disease warning system is an example of effective international scientific partnership contributing to the UN Sustainable Development Goals, said Sarah Millington, a scientific manager at Atmospheric Dispersion and Air Quality Group with the Met Office.

“Diverse expertise from the Met Office, the University of Cambridge and CIMMYT shows how combined fundamental research in epidemiology and meteorology modelling with field-based disease observation can produce a system that boosts smallholder farmers’ resilience to major agricultural challenges,” she said.

The atmospheric dispersion modeling was originally developed in response to the Chernobyl disaster and since then has evolved to be able to model the dispersion and deposition of a range of particles and gases, including biological particles such as wheat rust spores.

“The framework together with the underpinning technologies are transferable to forecast fungal disease in other regions and can be readily adapted for other wind-dispersed pests and disease of major agricultural crops,” said Christopher Gilligan, head of the Epidemiology and Modelling Group at the University of Cambridge.

Fungal wheat diseases are an increasing threat to farmer livelihoods in Asia

While there has been a history of wheat rust disease epidemics in South Asia, new emerging strains and changes to climate pose an increased threat to farmers’ livelihoods. The pathogens that cause rust diseases are continually evolving and changing over time, making them difficult to control.

Stripe rust threatens farmers in Afghanistan, India, Nepal and Pakistan, typically in two out of five seasons, with an estimated 43 million hectares of wheat vulnerable. When weather conditions are conducive and susceptible cultivars are grown, farmers can experience losses exceeding 70%.

Populations of stem rust are building at alarming rates and previously unseen scales in neighboring regions. Stem rust spores can spread across regions on the wind; this also amplifies the threat of incursion into South Asia and the ARRCC program’s target countries, underscoring the very real risk that the disease could reemerge within the subcontinent.

The devastating wheat blast disease, originating in the Americas, suddenly appeared in Bangladesh in 2016, causing wheat crop losses as high as 30% on a large area, and continues to threaten South Asia’s vast wheat lands.

In both cases, quick international responses through CIMMYT, the CGIAR research program on Wheat (WHEAT) and the Borlaug Global Rust Initiative have been able to monitor and characterize the diseases and, especially, to develop and deploy resistant wheat varieties.

The UK aid-funded ARRCC program is led by the Met Office and the World Bank and aims to strengthen weather forecasting systems across Asia. The program is delivering new technologies and innovative approaches to help vulnerable communities use weather warnings and forecasts to better prepare for climate-related shocks.

The early warning system uses data gathered from the online Rust Tracker tool, with additional fieldwork support from the Cereal Systems Initiative for South Asia (CSISA), funded by USAID and the Bill & Melinda Gates Foundation, both coordinated by CIMMYT.

Concerned experts ask world leaders to head off a global food security crisis from COVID-19

This story by Mike Listman was originally posted on the CIMMYT website.

Alarmed by the risk of global and regional food shortages triggered by the COVID-19 pandemic, a coalition of businesses, farmers’ groups, industry, non-governmental organizations, and academia has called on world leaders urgently to maintain open trade of their surplus food products.

Published by the Food and Land Use Coalition (FOLU) on April 9, 2020, and signed by 60 experts, the call to action urges world leaders to keep food supplies flowing, specially support vulnerable people, and finance sustainable, resilient food systems.

Covered by major world media, the declaration encourages governments to treat food production, processing, and distribution as an essential sector — similar to public health care — and thus to support continued, safe, and healthy activities by farmers and others who contribute to the sector, according to Martin Kropff, director general of the International Maize and Wheat Improvement Center (CIMMYT) and a signatory of the call to action.

“Consumers in low-income countries face the greatest threat of food insecurity,” said Kropff. “Their tenuous access to nutritious food is jeopardized when surplus food-producing nations choose to close trade as a defensive measure.”

Kropff added that many households in low-income countries depend on agriculture or related activities for their food and livelihoods. Their productivity and food security are compromised by illness or restrictions on movement or working.

“The call to action resonates with the findings of a landmark 2015 study by Lloyd’s of London,” he explained. “That work highlighted the fragility of global food systems in the event of coinciding shocks, an outcome that seems entirely possible now, given the health, cultural, and economic impacts of the COVID-19 pandemic.”

At the same time, the work of CIMMYT, other CGIAR centers, and their partners worldwide helps to stabilize food systems, according to Kropff.

“Our research outputs include high-yielding, climate-resilient crop varieties and more productive, profitable and sustainable farming methods,” he said. “These give farmers — and especially smallholders — the ingredients for more efficient and effective farming. They are grounded in reality through feedback from farmers and local partners, as well as socioeconomic studies on markets and value chains for food production, processing, and distribution.”

Conservation agriculture key in meeting UN Sustainable Development Goals

This story by Alison Doody was originally published on the CIMMYT website.

An international team of scientists has provided a sweeping new analysis of the benefits of conservation agriculture for crop performance, water use efficiency, farmers’ incomes and climate action across a variety of cropping systems and environments in South Asia.

The analysis, published today in Nature Sustainability, is the first of its kind to synthesize existing studies on conservation agriculture in South Asia and allows policy makers to prioritize where and which cropping systems to deploy conservation agriculture techniques. The study uses data from over 9,500 site-year comparisons across South Asia.

According to M.L. Jat, a principal scientist at the International Maize and Wheat Improvement Center (CIMMYT) and first author of the study, conservation agriculture also offers positive contributions to the Sustainable Development Goals of no poverty, zero hunger, good health and wellbeing, climate action and clean water.

“Conservation agriculture is going to be key to meet the United Nations Sustainable Development Goals,” echoed JK Ladha, adjunct professor at the University of California, Davis, and co-author of the study.

Scientists from CIMMYT, the Indian Council of Agricultural Research (ICAR), the University of California, Davis, the International Rice Research Institute (IRRI) and Cornell University looked at a variety of agricultural, economic and environmental performance indicators — including crop yields, water use efficiency, economic return, greenhouse gas emissions and global warming potential — and compared how they correlated with conservation agriculture conditions in smallholder farms and field stations across South Asia.

Results and impact on policy

Researchers found that many conservation agriculture practices had significant benefits for agricultural, economic and environmental performance indicators, whether implemented separately or together. Zero tillage with residue retention, for example, had a mean yield advantage of around 6%, provided farmers almost 25% more income, and increased water use efficiency by about 13% compared to conventional agricultural practices. This combination of practices also was shown to cut global warming potential by up to 33%.

This comes as good news for national governments in South Asia, which have been actively promoting conservation agriculture to increase crop productivity while conserving natural resources. South Asian agriculture is known as a global “hotspot” for climate vulnerability.

“Smallholder farmers in South Asia will be impacted most by climate change and natural resource degradation,” said Trilochan Mohapatra, Director General of ICAR and Secretary of India’s Department of Agricultural Research and Education (DARE). “Protecting our natural resources for future generations while producing enough quality food to feed everyone is our top priority.”

“ICAR, in collaboration with CIMMYT and other stakeholders, has been working intensively over the past decades to develop and deploy conservation agriculture in India. The country has been very successful in addressing residue burning and air pollution issues using conservation agriculture principles,” he added.

With the region’s population expected to rise to 2.4 billion, demand for cereals is expected to grow by about 43% between 2010 and 2050. This presents a major challenge for food producers who need to produce more while minimizing greenhouse gas emissions and damage to the environment and other natural resources.

“The collaborative effort behind this study epitomizes how researchers, policy-makers, and development practitioners can and should work together to find solutions to the many challenges facing agricultural development, not only in South Asia but worldwide,” said Jon Hellin, leader of the Sustainable Impact Platform at IRRI.

Crossing boundaries: looking at wheat diseases in times of the COVID-19 crisis

Disclaimer: The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the CGIAR Research Program on Wheat (WHEAT).

Daily life as we know it has grinded to a halt and crop scientists are pondering next steps in face of the global COVID-19 crisis. Hans Braun, Director of the Global Wheat Program at the International Maize and Wheat Improvement Center (CIMMYT) and the CGIAR Research Program on Wheat, joins us for a virtual chat to discuss the need for increased investment in crop disease research as the world risks a food security crisis. 

What have you learned from your work on contagious wheat diseases that we can take away during this time?

Wheat epidemics go back to biblical times. Wheat scientists now believe Egypt’s “seven bad years” of harvest referenced in the Bible were due to a stem rust outbreak.

So, we know what happens when we have a crop epidemic: diseases can completely wipe out a harvest. I have seen subsistence farmers stand in front of their swaying, golden wheat fields, but there is not a single grain inside the spikes. All because of wheat blast.

There are a lot of parallel issues that I see with COVID-19.

The epidemiology models for humans which we see now have a lot in common with plant epidemiology. For example, if you take a wheat field sown with a variety which is rust-resistant and then you get a spore which mutates and overcomes the resistance — like COVID 19 overcomes the human immune system — it then takes about two weeks for it to sporulate again and produce millions of these mutated spores. They sporulate once more and then you have billions and trillions of spores — then the wheat fields at the local, national and, in the worst case, regional level are severely damaged and in worst case are going to die.

The problem is that since we cannot quarantine wheat, if the weather is favorable these spores will fly everywhere and — just like with COVID-19 — they don’t need a passport to travel.

Could you elaborate on that? How can wheat diseases go global?

Usually it takes around 5 years, sometimes less, until a mutation in a rust spore can overcome the resistance of a wheat variety. Every so often, we see rust epidemics which cover an entire region. To monitor this movement, the Borlaug Global Rust Initiative of Cornell University and CIMMYT, funded by the Bill & Melinda Gates Foundation and DFID, established a global rust monitoring system that provides live data on spore movements.

For example, if you have a new race of stem rust in Yemen — and in Yemen wheat matures early — and then farmers burn the straw, their action “pushes” the spores up into the air, thus allowing them to enter the jet stream and cover 2,000 to 5,000 kilometers in a short period of time. Spores can also be carried on clothes or shoes by people who walked into an infected wheat field. Take Australia, for example, which has very strict quarantine laws. It is surrounded by sea and still eventually they get the new rust races which fly around or come with travelers. One just cannot prevent it.

Could climate change exacerbate the spreading of crop diseases?

Yes, the climate and its variability have a lot to do with it. For example, in the case of yellow rust, what’s extremely important is the time it takes from sporulation to sporulation. Take a rust spore. It germinates, then it grows, it multiplies and then once it is ready it will disperse and infect wheat plants. From one dispersal to the next it takes about two weeks.

In the last decades, in particular for yellow rust, new races are better adapted to high temperature and are multiplying faster. In a Nature paper, we showed that 30 years ago yellow rust was not present in the Great Plains in the US. Today, it is the most important wheat disease there. So there really is something going on and changing and that’s why we are so concerned about new wheat disease races when they come up.

What could an epidemiologist specialized in human viruses take from this?

Well, I think human epidemiologists know very well what happens in a case like COVID-19. Ordinary citizens now also start to understand what a pandemic is and what its related exponential growth means.

Maybe you should ask what policymakers can learn from COVID-19 in order to prevent plant epidemics. When it comes to epidemics, what applies to humans applies to plants. If there is a new race of a given crop disease, in that moment, the plant does not have a defense mechanism, like humans in the case of COVID-19, because we haven’t developed any immunity. While in developed countries farmers can use chemicals to control plant diseases, resource-poor farmers do not have this option, due to lack to access or if the plant protective has not been registered in their country.

In addition to this, our lines of work share a sense of urgency. If “doomsday” happens, it will be too late to react. At present, with a human pandemic, people are worried about the supply chain from food processing to the supermarket. But if we have an epidemic in plants, then we do not have the supply chain from the field to the food processing industry. And if people have nothing to eat, they will go to the streets and we will see violence. We simply cannot put this aside.

What other lessons can policymakers and other stakeholders take away from the current crisis?

The world needs to learn that we cannot use economics as the basis for disease research. We need to better foresee what could happen.

Let’s take the example of wheat blast, a devastating disease that can destroy the wheat spike and was initially confined to South America. The disease arrived in Bangladesh in 2016 and caused small economic damage, maybe 30,000 tons loss in a small geographic area — a small fraction of the national production but a disaster for the smallholder farmer, who thus would have lost her entire wheat harvest. The disease is now controlled with chemicals. But what if chemical resistance is developed and the disease spreads to the 10 million hectares in the Indo Gangetic Plains of India and the south of Pakistan. Unlikely? But what if it happens?

Agriculture accounts for 30% of the global GDP and the research money [going to agriculture] in comparison to other areas is small. Globally only 5% of R&D is invested in research for development related to agriculture. Such a discrepancy! A million U.S. dollars invested in wheat blast research goes a long way and if you don’t do it, you risk a disaster.

If there is any flip side to the COVID-19 disaster, it is that hopefully our governments realize that they have to play a much more serious role in many areas, in particular public health and disease control in humans but also in plants.

A Lloyd’s report concluded that a global food crisis could be caused by governments taking isolating actions to protect their own countries in response to a breadbasket failure elsewhere. I’m concerned that as the COVID-19 crisis continues, governments will stop exports as some did during the 2008 food price crisis, and then, even if there is enough food around, the 2008 scenario might happen again and food prices will go through the roof, with disastrous impact on the lives of the poorest.

Whole grains

This story by Emma Orchardson was originally published on the CIMMYT website.

The most recent dietary guidelines provided by the World Health Organization and other international food and nutrition authorities recommend that half our daily intake of grains should come from whole grains. But what are whole grains, what are their health benefits, and where can they be found?

What are whole grains?

The grain or kernel of any cereal is made up of three edible parts: the bran, the germ and the endosperm.

Each part of the grain contains different types of nutrients.

  • The bran is the multi-layered outer skin of the edible kernel. It is fiber-rich and also supplies antioxidants, B vitamins, minerals like zinc, iron, magnesium, and phytochemicals — natural chemical compounds found in plants that have been linked to disease prevention.
  • The germ is the core of the seed where growth occurs. It is rich in lipids and contains vitamin E, as well as B vitamins, phytochemicals and antioxidants.
  • The largest portion of the kernel is the endosperm, an interior layer that holds carbohydrates, protein and smaller amounts of vitamins and minerals.
The grain or kernel of maize and wheat is made up of three edible parts: the bran, the germ and the endosperm. (Graphic: Nancy Valtierra/CIMMYT)
The grain or kernel of maize and wheat is made up of three edible parts: the bran, the germ and the endosperm. (Graphic: Nancy Valtierra/CIMMYT)

A whole grain is not necessarily an entire grain.

The concept is mainly associated with food products — which are not often made using intact grains — but there is no single, accepted definition of what constitutes a whole grain once parts of it have been removed.

Generally speaking, however, a processed grain is considered “whole” when each of the three original parts — the bran, germ and endosperm — are still present in the same proportions as when the original one. This definition applies to all cereals in the Poaceae family such as maize, wheat, barley and rice, and some pseudocereals including amaranth, buckwheat and quinoa.

Wholegrain vs. refined and enriched grain products

Refined grain products differ from whole grains in that some or all of the outer bran layers are removed by milling, pearling, polishing, or degerming processes and are missing one or more of their three key parts.

For example, white wheat flour is prepared with refined grains that have had their bran and germ removed, leaving only the endosperm. Similarly, if a maize kernel is degermed or decorticated — where both the bran and germ are removed — it becomes a refined grain.

The main purpose of removing the bran and germ is technological, to ensure finer textures in final food products and to improve their shelf life. The refining process removes the variety of nutrients that are found in the bran and germ, so many refined flours end up being enriched — or fortified — with additional, mostly synthetic, nutrients. However, some components such as phytochemicals cannot be replaced.

A hand holds grains of wheat. (Photo: Thomas Lumpkin/CIMMYT)
A hand holds grains of wheat. (Photo: Thomas Lumpkin/CIMMYT)

Are wholegrain products healthier than refined ones?

There is a growing body of research indicating that whole grains offer a number of health benefits which refined grains do not.

Bran and fiber slow the breakdown of starch into glucose, allowing the body to maintain a steady blood sugar level instead of causing sharp spikes. Fibers positively affect bowel movement and also help to reduce the incidence of cardiovascular diseases, the incidence of type 2 diabetes, the risk of stroke, and to maintain an overall better colorectal and digestive health. There is also some evidence to suggest that phytochemicals and essential minerals — such as copper and magnesium — found in the bran and germ may also help protect against some cancers.

Despite the purported benefits, consumption of some wholegrain foods may be limited by consumer perception of tastes and textures. The bran in particular contains intensely flavored compounds that reduce the softness of the final product and may be perceived to negatively affect overall taste and texture. However, these preferences vary greatly between regions. For example, while wheat noodles in China are made from refined flour, in South Asia most wheat is consumed wholegrain in the form of chapatis.

Popcorn is another example of a highly popular wholegrain food. It is a high-quality carbohydrate source that, consumed naturally, is not only low in calories and cholesterol, but also a good source of fiber and essential vitamins including folate, niacin, riboflavin, thiamin, pantothenic acid and vitamins B6, A, E and K. One serving of popcorn contains about 8% of the daily iron requirement, with lesser amounts of calcium, copper, magnesium, manganese, phosphorus, potassium and zinc.

Boiled and roasted maize commonly consumed in Africa, Asia and Latin America are other sources of wholegrain maize, as is maize which has been soaked in lime solution, or “nixtamalized.” Depending on the steeping time and method of washing the nixtamalized kernels, a portion of the grains used for milling could still be classed as whole.

Identifying wholegrain products

Whole grains are relatively easy to identify when dealing with unprocessed foods such as brown rice or oats. It becomes more complicated, however, when a product is made up of both whole and refined or enriched grains, especially as color is not an indicator. Whole wheat bread made using whole grains can appear white in color, for example, while multi-grain brown bread can be made primarily using refined flour.

In a bid to address this issue, US-based nonprofit consumer advocacy group the Whole Grains Council created a stamp designed to help consumers identify and select wholegrain products more easily. As of 2019, this stamp is used on over 13,000 products in 61 different countries.

However, whether a product is considered wholegrain or not varies widely between countries and individual agencies, with a lack of industry standardization meaning that products are labelled inconsistently. Words such as “fiber,” “multigrain” and even “wholegrain” are often used on packaging for products which are not 100% wholegrain. The easiest way to check a product’s wholegrain content is to look at the list of ingredients and see if the flours used are explicitly designated as wholegrain. These are ordered by weight, so the first items listed are those contained more heavily in the product.

As a next step, an ad-hoc committee led by the Whole Grain Initiative is due to propose specific whole grain quantity thresholds to help establish a set of common criteria for food labelling. These are likely to be applied worldwide in the event that national definitions and regulations are not standardized.

CGIAR’s Response to COVID-19

This article was originally posted on the CGIAR website.

Photo: Eneas De Troya/Flickr.

The novel coronavirus (COVID-19) continues to spread rapidly. Since its start in China in December, the outbreak has spread to more than 100 countries, endangering the health and livelihoods of millions. To contain the pandemic, many cities and regions across the world have been shut down, putting a halt to day-to-day activities.

As Western economies struggle with difficult decisions – it is those in the global South that are most at risk. Economies that are dependent on tourism, trade and foreign investment have fewer options at their disposal.

An urgent and coordinated global response is needed – from the global to the local level to protect populations – and especially the most vulnerable. Food security is fragile under normal circumstances and must not be ignored as part of a One Health strategy.

CGIAR, as the world’s largest public research network on food systems, provides evidence to help understand and address threats to food and nutrition security from the COVID-19 pandemic, such as:

  • The food system has been significantly affected, and these impacts will grow if processing enterprises cannot restart production in a near future;
  • Production of staple food crops such as wheat, rice, and vegetables will be affected if the outbreak continues into critical planting periods;
  • Domestic and international trade disruptions may trigger food price panics;
  • Restrictions on mobility may lead to labor shortages.

CGIAR will make available its latest research and analysis on COVID-19 to support authorities and the public in making informed decisions during the current crisis. In the research and news featured below, CGIAR scientists provide evidence-based advice and recommendations on:

  • Introducing enabling policies for spring planting and increasing support for production entities;
  • Ensuring the smooth flow of trade and making full use of the international market as a vital tool to secure food supply and demand;
  • Ensuring smooth logistical operations of regional agricultural and food supply chains;
  • Monitoring food prices and strengthening market supervision;
  • Protecting vulnerable groups and providing employment services to migrant workers;
  • Regulating wild food markets to curb the source of the disease;
  • Measuring impact on small and medium-sized businesses;
  • Analyzing how much global poverty will increase because of COVID-19.