Researchers are hunting for the “climate gene” that can save food plants
If plants are to adapt to a harsher climate, they must have genes that tolerate stress. Read more here.
research: Genetic resources
Large-scale genomics will improve the yield, climate-resilience, and quality of bread wheat, new study shows
Using the full wheat genome map published in 2018, combined with data from field testing of wheat breeding lines in multiple countries, an international team of scientists has identified significant new chromosomal regions for wheat yield and disease resistance and created a freely-available collection of genetic information and markers for more than 40,000 wheat lines.
Reported today in Nature Genetics, the results will speed up global efforts to breed more productive and climate-resilient varieties of bread wheat, a critical crop for world food security that is under threat from rising temperatures, rapidly-evolving fungal pathogens, and more frequent droughts, according to Philomin Juliana, wheat scientist at the International Maize and Wheat Improvement Center (CIMMYT) and first author of the new study.
“This work directly connects the wheat genome reference map with wheat lines and extensive field data from CIMMYT’s global wheat breeding network,” said Juliana. “That network in turn links to over 200 breeding programs and research centers worldwide and contributes to yield and other key traits in varieties sown on nearly half the world’s wheat lands.”
The staple food for more than 2.5 billion people, wheat provides 20% of human dietary calories and protein worldwide and is critical for the nutrition and food security of hundreds of millions of poor persons in regions such as North Africa and South Asia.
“Farmers and societies today face new challenges to feed rising and rapidly-urbanizing populations, and wheat epitomizes the issues,” said Ravi Singh, CIMMYT wheat breeder and corresponding author of the study. “Higher temperatures are holding back yields in major wheat-growing areas, extreme weather events are common, crop diseases are spreading and becoming more virulent, and soil and water are being depleted.”
Juliana said the study results help pave the way to apply genomic selection, an approach that has transformed dairy cow husbandry, for more efficient wheat breeding.
“Molecular markers are getting cheaper to use; meanwhile, it’s very costly to do field testing and selection involving many thousands of wheat plants over successive generations,” Juliana said. “Genome-wide marker-based selection can help breeders to precisely identify good lines in early breeding generations and to test plantlets in greenhouses, thereby complementing and streamlining field testing.”
The new study found that genomic selection could be particularly effective in breeding for wheat end-use quality and for resistance to stem rust disease, whose causal pathogen has been evolving and spreading in the form of highly-virulent new races.
The new study also documents the effectiveness of the global public breeding efforts by CIMMYT and partners, showing that improved wheat varieties from this work have accumulated multiple gene variants that favor higher yields, according to Hans-Joachim Braun, director of CIMMYT’s global wheat program.
“This international collaboration, which is the world’s largest publicly-funded wheat breeding program, benefits farmers worldwide and offers high-quality wheat lines that are released directly to farmers in countries, such as Afghanistan, that are unable to run a full-fledged wheat breeding program,” Braun explained.
The study results are expected to support future gene discovery, molecular breeding, and gene editing in wheat, Braun said.
Together with more resource-efficient cropping systems, high-yielding and climate-resilient wheat varieties will constitute a key component of the sustainable intensification of food production described in Strategy 3 of the recent EAT-Lancet Commission recommendations to transform the global food system. Large-scale genomics will play a key role in developing these varieties and staying ahead of climate- and disease-related threats to food security.
Funders of this work include USAID’s Feed the Future Innovation Lab for Applied Wheat Genomics. Contributing to the research described are research teams engaged in wheat improvement at CIMMYT, and the lab of Jesse Poland, Associate Professor at Kansas State University and Director of the USAID Applied Wheat Genomics Innovation Lab.
For more information, or to arrange interviews with the researchers, please contact:
Marcia MacNeil, Wheat Communications Officer, CIMMYT
M.MacNeil@cgiar.org, +52 (55) 5804 2004, ext. 2070
Back from the brink of extinction
In the early 20th century, Aaron Aaronsohn, a prominent agronomist best known for identifying the progenitor of wheat, began looking for durum wheat landraces in Israel. He traveled to villages across the country, carefully collecting and recording details of the local varieties used in each area.
This task was not without purpose. Aaronsohn recognized that as increasing numbers of settlers like himself came to the territory, the varietal change from the introduction of new and competitive wheat varieties and the rapid intensification of agriculture would soon cause all the traditional structures he had identified to disappear.
Aaronsohn was one of the first to begin collecting germplasm in the region, but others saw the importance of collecting before large-scale change occurred. For example, Russian botanist Nikolai Vavilov gathered samples from Israel on one of his expeditions through the Middle East. By the end of the century, a number of collections had been established, but overall efforts at conservation were fragmented.
“That’s why we say the collection was on the verge of extinction,” explains Roi Ben-David, a researcher at the Volcani Center, Israel’s Agricultural Research Institute (ARO). “There were single accessions in genebanks around the world but no one really gave them special treatment or saw their value. Many were in private collections; others were simply lost.”
When Ben-David and his colleagues began looking for landraces six years ago, even the collection housed at the Israeli Genebank (IGB) was disappointing, with many samples stored in unmarked boxes in sub-optimal conditions. “When we came in nobody was really trying to study what we had and put it together to represent the area’s wheat landscape as it was 100 years ago.”
Long-term efforts to restore and conserve a collection of Israeli and Palestinian wheat landraces (IPLR) have led to the restoration of 930 lines so far, but there are many varieties that cannot be recovered. Therefore, it came as a great surprise to Ben-David when he arrived at the International Maize and Wheat Improvement Center (CIMMYT) headquarters in Mexico and stumbled upon one of the collections presumed lost. “I think it was actually my first week at CIMMYT when I spotted a demonstration plot growing one of the lost varieties — a subset of the Ephrat-Blum collection — and I couldn’t believe it.”
He had heard about this collection from the late Abraham Blum, but had never been able to locate it. “Someone might have moved the seeds, or maybe the box was not well labelled and thrown out. We don’t know, but needless to say it was a very good surprise to rediscover 64 of our missing lines.”
What prompted you and your colleagues to start looking for landraces in Israel?
We began because we recognized local landraces are good genetic resources but unfortunately, we couldn’t find any. It wasn’t so much that they didn’t exist, but the accessions were scattered across the world, mostly in private collections in countries like the USA or Australia. The Israeli Genebank, which sits only two floors above my office, had a few buckets of germplasm but nobody really knew what was inside.
The Middle East and the Fertile Crescent are centers of diversity, not only for wheat but for all crops that were part of the Neolithic revolution 10,000 years ago. They started here – the exact point of origin was probably in what is now southeast Turkey – so we have had thousands of years of evolution in which those landraces dominated the agricultural landscape and adapted to different environments.
Why do you think so much of the collection was lost?
The lines from Israel were lost because their conservation simply wasn’t prioritized. Losses happen everywhere but what was missing in this case was the urgency and understanding of just how important these collections are. Luckily, the current manager of the IGB, who is a fundamental partner in building the IPLR, understood the need to prioritize this and allocated a budget to conserve it as one collection.
What is the value of conserving landraces and why should it be prioritized?
Landraces are an extremely important genetic resource. Wild relatives are the biggest treasure, but breeders are usually reluctant to use them because they are so very different from modern varieties. So landraces form the link between these two, having already been domesticated and developed within farming systems while remaining genetically distinct from the modern. In wheat, they’re quite easy to spot because of how tall they are compared to the semi-dwarf varieties that replaced them in the 20th century.
There are two main reasons why we need to prioritize conservation. First, we believe that the evolution under domestication in this region is important to the community as a whole. Second, it is now a critical time, as we’re getting further from the time in which those traditional lines were in use. The last collection was carried out in the 1980s, when people were still able to collect authentic landraces from farmers but this is just not possible any more. We travelled all over the country but the samples we collected were not authentic – most were modern varieties that farmers thought were traditional. Not everybody knows exactly what they’re growing.
The time factor is critical. If we were to wake up 50 years from now and decide that it’s important to start looking for landraces, I don’t know how much we could actually save.
Are there any farmers still growing landraces in Israel?
When we started looking for farmers who are still growing landraces we only found one farm. It is quite small – only about ten acres shared between two brothers. They grow a variety which is typically used to make a traditional food called kube, a kind of meat ball covered in flour and then then either fried or boiled. If you boil it using regular flour it falls apart, so people prefer to use a landrace variety, which is what the brothers grow and are able to sell for up to six times as much as regular durum wheat in the market. However, they’re not really interested in getting rich; they’re just trying to keep their traditions alive.
How are you and your colleagues working to conserve the existing collection?
There are two approaches. We want to develop is ex-situ conservations to preserve the diversity. As landraces are not always easy to conserve in a genebank, we also want to support in-situ conservation in the field, like traditional farmers have done. Together with the IGB we’ve distributed seed to botanical gardens and other actors in the hope that at least some of them will propagate it in their fields.
Having established the collection, we’re also trying to utilize it for research and breeding as much as possible. So far we’ve characterized it genetically, tested for drought tolerance and other agronomic traits and we’re in talks to start testing the quality profile of the lines.
Did you continue working on this while you were based at CIMMYT?
Yes, this was an additional project I brought with me during my sabbatical. The main success was working with Carolina Sansaloni and the team at the Genetic Resources program to carry out the genotyping. If it were left to my own resources, I don’t think we could have done it as the collection contains 930 plant genotypes and we only had the budget to do 90.
Luckily, CIMMYT also has an interest in the material so we could collaborate. We brought the material, CIMMYT provided technical support and we were able to genotype it all, which is a huge boost for the project. We had already been measuring phenotypes in Israel, but now that we have all the genetic data as well we can study the collection more deeply and start looking for specific genes of interest.
What will happen to the lines you discovered at CIMMYT?
They’ve been sent back to Israel to be reintegrated into the collection. I want to continue collaborating with people in CIMMYT’s Genetic Resources program and genebank to do some comparative genomics and assess how much diversity we have in the IPLR collection compared with what CIMMYT has. Is there any additional genetic diversity? How does it compare to other landraces collections? That is what we want to find out next.
Roi Ben-David is based at Israel’s Agricultural Research Organization (ARO). He works in the Plant Institute, where his lab focuses on breeding winter cereals such as wheat. He has recently completed a one-year sabbatical placement at the International Maize and Wheat Improvement Center (CIMMYT).
CIMMYT’s germplasm banks contain the largest and most diverse collections of maize and wheat in the world. Improved and conserved seed is available to any research institution worldwide.
Ethiopian policymakers consider wider use of DNA fingerprinting
How to track adoption and assess the impact of maize and wheat varieties? Some of the methods used until now, like farmers’ recall surveys, have various limitations. In addition to relying exclusively on people’s memory and subjectivity, they are difficult to replicate and prone to errors.
DNA fingerprinting, on the other hand, allows objective evaluation and is considered the “gold standard” method for adoption and impact assessments.
It consists of a chemical test that shows the genetic makeup of living things, by separating strands of DNA and revealing the unique parts of their genome. The results show up as a pattern of stripes that can be matched against other samples.
This technique is extremely helpful in tracking crop varieties and monitoring their adoption. It can be used to assess the impact of research-for-development investments, guide breeding and seed system strategies, implement the intellectual property rights of breeders, assess the use of crop genetic resources, and informing policy.
On June 25, 2019, the International Maize and Wheat Improvement Center (CIMMYT) held a half-day workshop in Addis Ababa to discuss the use and application of DNA fingerprinting in Ethiopia for the tracking of crop varieties.
High-level government officials and major players in the agricultural sector were interested in learning more about the policy implications of this tool and how to mainstream its use.
Introducing DNA fingerprinting in Ethiopia
The main DNA fingerprinting project in Ethiopia has been in operation since January 2016, focusing on the country’s two major staple crops: wheat and maize. The project covers the Amhara, Oromia, SNNPR, and Tigray regions, which together account for 92% and 79% of the national wheat and maize production.
The Bill & Melinda Gates Foundation has funded the project, which was jointly implemented by CIMMYT, the Ethiopian Institute of Agricultural Research (EIAR), Ethiopia’s Central Statistical Agency (CSA) and Diversity Arrays Technology (DArT).
The main objective of the project was to generate a knowledge base for the practical use of DNA fingerprinting, to mainstream the use of this technology, and to offer policy options and recommendations.
Better monitoring for wheat self-sufficiency
At the workshop, researchers presented two policy briefs specific to Ethiopia: one focusing on policy implications of DNA fingerprinting for tracking bread wheat varieties and another one on how to revitalize the durum wheat sub-sector.
Speaking at the workshop, Eyasu Abraha, Minister of Agriculture and Natural Resources, noted that the government planned to achieve wheat grain self-sufficiency in the next few years by increasing wheat productivity in the highlands and expanding wheat production to the lowlands through irrigation. In this regard, improved crop variety development and dissemination is one of the key elements to increase agricultural productivity and improve the livelihood of millions of smallholder farmers.
According to Abraha, more than 130 wheat varieties have been released or registered in Ethiopia since the late 1960s, in collaboration with international research organizations. Public and private seed enterprises have multiplied and distributed these varieties to reach smallholder farmers.
Even though adoption studies have been conducted, there is still a strong need for more accurate and wider studies. In addition to tracking adoption and demand, using DNA fingerprinting could help understand the distribution of varieties across space and time.
Genome editing, gene drives, and synthetic biology: Will they contribute to disease-resistant crops, and who will benefit?
Ensuring the access of small-scale farmers to products and potential benefits from genetic engineering (GE) technologies for agriculture will require concerted investment and research by public institutions worldwide and particularly in low- and middle-income countries.
This was a key conclusion of a new review paper describing cutting-edge GE applications that offer exciting options to enhance the disease and pest resistance of important food crops and the ecological sustainability of cropping systems.
The technologies include gene editing (site-specific changes to DNA in a genome), gene drives (greatly enhancing or reducing frequency of genes that affect insect or pathogen reproduction), and synthetic biology (re-design or construction of biological devices, for example chromosomes or organelles).
Authored by international experts in policy, socioeconomics, and biological science, the new paper outlines potential uses of the technologies, particularly to address problems that affect resource-poor farmers or consumers, such as the viruses that attack cassava, the Striga weed that is a parasite of maize, or the fungal pathogen of groundnut that produces deadly toxins.
A weak capacity for research and development in many countries, combined with a small and declining public investment, raises questions about those nations’ ability to develop and deliver high-quality GE technologies or realize their benefits.
“The concern is that farmers not served by leading companies, who are developing the technologies, will be unable to obtain new, resistant crop varieties or other products of these technologies,” said Kevin Pixley, director of the genetic resources program of the International Maize and Wheat Improvement Center (CIMMYT) and first author of the new paper.
The technologies have already proven effective for controlling bacterial, fungal, and viral plant pathogens, as well as insects that transmit them. For example, GE approaches to control cassava brown streak disease and cassava bacterial blight—for which there are few or no known sources of resistance in cassava itself—appear on track to produce resistant versions of cassava.
Future gene drive technologies that can be kept within specific areas and reversed if needed may offer ways to control insects that carry plant diseases or weeds that damage crops, and synthetic biology could someday create plants that are immune to invading viruses.
“The private sector is likely to invest mainly in major crops and major traits that will bring them profits, so work on minor, perennial, clonal, or staple food crops of lower-income countries may suffer,” said José Falck-Zepeda, senior research fellow and leader of the policy team in the program for biosafety systems of the International Food Policy Research Institute (IFPRI) and a co-author of the review paper.
Many countries are still deciding whether and how they will regulate new GE products. The new paper explains how key factors including the cost and complexity of complying with biosafety regulations will shape the potential distribution of the technologies and products, determining which institutions undertake the related research and, as a result, which traits and crops are studied.
Civil society concerns regarding GE technologies and how or by whom they are deployed add important considerations to the complex questions surrounding the use of GE products.
“Realizing the potential of GE crops will require investments and policies for research, intellectual property regimes, and regulatory frameworks,” say the authors, “and societies must also address legitimate concerns about their responsible stewardship, agroecological sustainability, and equitable access to associated benefits.”
An open-access version of the full paper is available online:
https://doi.org/10.1146/annurev-phyto-080417-045954
Pixley, K.V., J.B. Falck-Zepeda, K.E. Giller, L.L. Glenna, F. Gould, C.A. Mallory-Smith, D.M. Stelly, and C.N. Stewart. 2019. Genome editing, gene drives, and synthetic biology: Will they contribute to disease-resistant crops, and who will benefit? Annu. Rev. Phytopathol 57:8.1–8.24.
See also the related feature by the International Food Policy Research Institute (IFPRI):
Will genetic engineering contribute to disease-resistant crops, and who will benefit?
CIMMYT research at the forefront of the digital revolution in African agriculture
At the African Green Revolution Forum 2019, global and African leaders come together to develop actionable plans that will move African agriculture forward. This year, the forum is taking place in Ghana on the week of September 3, 2019, under the theme “Grow digital: Leveraging digital transformation to drive sustainable food systems in Africa.” Participants will explore the practical application of the emerging elements of the digital era such as big data, blockchain, digital IDs, drones, machine learning, robotics, and sensors.
CIMMYT’s work in this area is showcased in a new leaflet entitled “Data-driven solutions for Africa: Using smart tools to combat climate change.” The leaflet highlights innovations such as crowdsourced crop disease tracking and response systems in Ethiopia, low-cost imaging tools to speed up the development of hardier varieties, and combining geospatial data with crop models to predict climate change and deliver personalized recommendations to farmers.
Speaking at the conference attended by 2,000 delegates and high-level dignitaries, CIMMYT Director General Martin Kropff will give the keynote remarks during the session “Digital innovations to strengthen resilience for smallholders in African food systems” on September 3. This panel discussion will focus on how the data revolution can support African smallholder farmers to adapt quickly challenges like recurrent droughts or emerging pests, including the invasive fall armyworm. The Global Resilience Partnership (GRP), the Food and Agriculture Organization of the United Nations (FAO), CABI, and the Minister of Agriculture of Burkina Faso will be among the other panelists in the session.
The same day, CIMMYT will also participate to an important “Agronomy at scale through data for good” panel discussion with speakers from the Bill & Melinda Gates Foundation, research organizations and private companies. The session will highlight how digital agriculture could help deliver better targeted, site-specific agronomic advice to small farmers.
During the forum, the CIMMYT delegation will seek collaborations in other important drivers of change like gender transformation of food systems and smallholder mechanization.
They will join public sector leaders, researchers, agri-preneurs, business leaders and farmers in outlining how to leverage the growth in digital technologies to transform food systems and agricultural livelihoods in Africa.
More with less: Research for intensified food production with scarcer resources and heating climates
After declining for nearly a decade to around 770 million, in the last three years the number of hungry people has shot up to more than 850 million. At the same time, erratic weather and crop pests and diseases are ruining harvests, intensifying farmers’ risks, and threatening local and global food security.
In an article for Rural 21, I describe how plant breeding has changed over the last four decades and which methods the international research community is developing to master present and future challenges.
Read the full article
Amos Emitati Alakonya
Amos Alakonya is head of CIMMYT’s Seed Health Unit. Through rigorous laboratory seed testing and field inspections of seed nurseries, he works to ensure that seed received and distributed by CIMMYT scientists is free from pests and diseases. His team also provides quarantine support to CIMMYT stations during disease outbreaks to minimize losses from emerging diseases.
Experimental stations in Mexico improve global agriculture
The International Maize and Wheat Improvement Center (CIMMYT) operates five agricultural experiment stations in Mexico. Strategically located across the country to take advantage of different growing conditions — spanning arid northern plains to sub-tropical and temperate climatic zones — the stations offer unique and well-managed testing conditions for a variety of biotic and abiotic stresses.
Heat and drought tolerance in wheat is the focus of study at Ciudad Obregón, while the humid, cool conditions at Toluca are ideal for studying wheat resistance to foliar diseases. The tropical and sub-tropical settings of Agua Fría and Tlaltizapán respectively are suited to maize field trials, while at El Batán researchers carry out a wide variety of maize and wheat trials.
A new video highlights the important and valuable contribution of the five experimental stations in Mexico to CIMMYT’s goal of developing maize and wheat that can cope with demanding environments around the world, helping smallholder farmers in Africa, Asia and Latin America adapt to challenges like climate change, emerging pests and disease, and malnutrition.
Featuring aerial cinematography and interviews with each station’s manager, the video takes viewers on a journey to each experimental station to highlight the research and management practices specific to each location.
In addition to their role in breeding maize and wheat varieties, CIMMYT’s experimental stations host educational events throughout the year that train the next generation of farmers, policymakers and crop scientists. They also provide the canvas on which CIMMYT scientists develop and test farming practices and technologies to help farmers grow more with less.
Some of the stations also hold historical significance. Ciudad Obregón and Toluca are two of the sites where Norman Borlaug set up his shuttle breeding program that provided the foundations of the Green Revolution. It was also in Toluca, while at a trial plot alongside six young scientists from four developing nations, where Borlaug first received news of his 1970 Nobel Peace Prize award.
Annual Report 2018 launched
Read or download the full report in PDF format
Read the web version of the report
In 2018, CIMMYT continued to innovate and forge strategic alliances to combat malnutrition, tackle the effects of climate change and respond to emerging threats.
Building on the release of a new wheat genome reference map, our researchers more precisely tagged genes for valuable traits, including disease resistance, heat tolerance, and grain quality, in more than 40,000 CIMMYT wheat lines.
In collaboration with our partners, CIMMYT released 81 maize and 48 wheat varieties. More than 40,000 farmers, scientists and technical workers across the world took part in over 1,500 training and capacity development activities. CIMMYT researchers published 338 journal articles.
As the maize-hungry fall armyworm spreads from Africa to Southeast Asia, CIMMYT joined with more than 40 partners in an international consortium to advance research against the devastating insect pest.
CIMMYT used a scaling approach to extend the benefits of crop research to more farmers and consumers in developing countries in transformative and lasting ways. Smallholder farmers in Mexico, Pakistan and Zimbabwe are benefitting from the use of appropriate machinery and implements for efficient and climate-smart agriculture. A manual developed with the Food and Agriculture Organization (FAO) of the United Nations offers technical and business advice for local entrepreneurs offering mechanized services, such as sowing or threshing, to smallholder farmers.
As part of taste tests in Ethiopia, Kenya, and Tanzania, consumers indicated their willingness to pay a premium for quality protein maize (QPM), which contains enhanced levels of the amino acids needed to synthesize protein.
A CIMMYT-led study on gender has explored the lives and viewpoints of 7,500 men and women from farming communities in 26 countries, providing invaluable information that will lead to better productivity and food security.
2018 showed us that the passion and values of staff and partners help CIMMYT to have major impact on the livelihoods of smallholders and the poor. This Annual Report pays tribute to them.
Read or download the full report in PDF format
Read the web version of the report
Space data applications for wheat and maize research
In 2017, a call for proposals from Copernicus Climate Change Service Sectoral Information Systems led the International Maize and Wheat Improvement Center (CIMMYT to collaborate with Wageningen University, the European Space Agency (ESA), and other research and meteorological organizations to develop practical applications in agricultural and food security for satellite-sourced weather data.
The project, which recently ended, opened the door to a wide variety of potential uses for this highly detailed data.
ESA collects extremely granular data on weather, churned out at an hourly rate. CIMMYT researchers, including Foresight Specialist Gideon Kruseman, reviewed this data stream, which generates 22 variables of daily and sub-daily weather data at a 30-kilometerlevel of accuracy, and evaluated how it could help generate agriculture-specific weather and climate data sets.
“For most people, the reaction would be, ‘What do we do with this?’ Kruseman said. “For us, this is a gold mine.”
For example, wind speed — an important variable collected by ESA satellites — is key for analyzing plant evaporation rates, and thus their drought tolerance. In addition, to date, information is available on ideal ago-climatic zones for various crop varieties, but there is no data on the actual weather conditions during a particular growing season for most sites.
By incorporating the information from the data sets into field trial data, CIMMYT researchers can specifically analyze maize and wheat cropping systems on a larger scale and create crop models with higher precision, meaning that much more accurate information can be generated from the trials of different crop varieties.
The currently available historic daily and sub-daily data, dating back to 1979, will allow CIMMYT and its partners to conduct “genotype by environment (GxE)” interaction analysis in much higher detail. For example, it will allow researchers to detect side effects related to droughts and heat waves and the tolerance of maize and wheat lines to those stresses. This will help breeders create specific crop varieties for farmers in environments where the impact of climate change is predicted to be more apparent in the near future.
“The data from this project has great potential fix this gap in information so that farmers can eventually receive more targeted assistance,” said Kruseman.
These ideas are just the beginning of the agricultural research and food security potential of the ESA data. For example, Kruseman would like to link the data to household surveys to review the relationship between the weather farmers experience and the farming decisions they make.
By the end of 2019, the data will live on an open access, user-friendly database. Eventually, space agency-sourced weather data from as far back as 1951 to as recent as five days ago will be available to researchers and weather enthusiasts alike.
Already CIMMYT scientists are using this data to understand the potential of a promising wheat line, for seasonal forecasting, to analyze gene-bank accessions and for a statistical analysis of maize trials, with many more high-impact applications expected in the future.
Rebuttal letter sets the record straight on crop breeding for climate change resilience
In early 2019, an article published by European climate researchers in the Proceedings of the National Academy of Science (PNAS) journal questioned the climate resilience of modern wheat varieties. The article suggested that modern wheat varieties showed reduced climate resilience as a direct result of modern breeding methods and practices, a claim that researchers at the International Maize and Wheat Improvement Center (CIMMYT) vehemently rebuke.
In a rebuttal letter published in the June issue of PNAS a group of scientists, including CIMMYT’s Susanne Dreisigacker and Sarah Hearne, strongly contradict the finding that breeding has reduced climate resilience in European wheat, citing significant flaws in the authors’ methodology, data analyses and interpretation.
“This article discredits European plant breeders and wheat breeders in general, who have been working over many decades to produce a wide range of regionally adapted, stable varieties which perform well under a broad range of climate change conditions,” said CIMMYT wheat molecular geneticist Susanne Dreisigacker.
Among other flaws, they found a number of omissions and inconsistencies.
- The article shows a lack of understanding of commonly used terms and principles of breeding theory, criticizing newer wheat varieties for demonstrating a decrease in “climatic response diversity.” Less diversity in wheat response — that is, more stable yields despite the influence of climate change — is a benefit, not a threat, to farmers.
- The article authors contradict the common knowledge among farmers and plant breeders that new elite wheat varieties are generally more productive than older varieties; new cultivars are only approved if they show added value in direct comparison to existing varieties.
- The article’s claim of long-term losses of climate resilience in “European wheat” is unsubstantiated. The authors extensively used data from three small countries — the Czech Republic, Denmark and Slovakia — which contribute less than five percent of Europe’s wheat supply. Three of the five most important wheat producers in Europe — Russia, Ukraine and the United Kingdom — were not accounted for in the analysis.
- The authors failed to report the actual wheat yields in their study, neglected to publish the underlying data with the manuscript and have up to now declined requests to make the data available.
Europe is one of the world’s major wheat producers and threats to its wheat production due to climate change would have serious consequences for world’s food security. Luckily, say the scientists who published the rebuttal letter, this fear is unfounded.
“Wheat producers and bread consumers around the world will be relieved to learn that breeders have not ignored climate change after all,” said letter lead-author Rod Snowdon, from the Department of Plant Breeding at Justus Liebig University of Giessen, Germany.
The full rebuttal letter by 19 international plant breeders, agronomists and scientists, is available on the PNAS site and reprinted in its entirety below.
Reduced response diversity does not negatively impact wheat climate resilience
Kahiluoto et al. (1) assert that climate resilience in European wheat has declined due to current breeding practices. To support this alarming claim, the authors report yield variance data indicating increasingly homogeneous responses to climatic fluctuations in modern wheat cultivars. They evaluated “response diversity,” a measure of responses to environmental change among different species jointly contributing to ecosystem functions (2). We question the suitability of this measure to describe agronomic fitness in single-cultivar wheat cropping systems. Conclusions are made about “long-term trends,” which in fact span data from barely a decade, corresponding to the duration of a single wheat breeding cycle. The authors furthermore acknowledge increasing climate variability during the study period, confounding their analysis of climate response in the same time span.
The underlying data are not published with the manuscript. Thus, the assertion that there is “no inherent trade-off between yield potential and diversity in weather responses” (1) cannot be verified. Inexplicably, the analysis and conclusions ignore absolute yields, which increase over time through breeding (3–6). Furthermore, incompatible data from completely different ecogeographical forms and species of wheat are apparently considered together, and the dataset is strongly biased toward a few small countries with minimal wheat production and narrow agroclimatic gradients.
The study assumes that increased response diversity among different cultivars is associated with yield stability. In contrast, the common, agronomic definition of yield stability refers to the ability of a single cultivar to stably perform well in diverse environments, without excessive responses to fluctuating conditions. Response diversity measures that ignore absolute yield do not support statements about food security or financial returns to farmers.
Cultivar yield potential, stability, and adaptation are enhanced by multienvironment selection over long breeding time frames, encompassing climate fluctuations and a multitude of other relevant environmental variables. Translation to on-farm productivity is promoted by national registration trials and extensive, postregistration regional variety trials in diverse environments. The unsurprising conclusion that planting multiple cultivars enhances overall production stability mirrors longstanding farming recommendations and practice (7). The availability of robust performance data from a broad range of high-performing cultivars enables European farmers to manage their production and income risks.
Kahiluoto et al. (1) speculate about “genetic erosion” of modern cultivars due to a “lack of incentives for breeders to introduce divergent material.” To substantiate these claims, the authors cite inadequate genetic data from non-European durum wheat (8), while explicitly dismissing clearly opposing findings about genetic diversity in European bread wheat (9). Short-term reductions in response diversity in five countries were misleadingly reported as a “long-term decline” in climate resilience in “most European countries,” although six out of seven countries with sufficient data showed no long-term decline. The article from Kahiluoto et al. and the misrepresentation of its results distorts decades of rigorous, successful breeding for yield potential and stability in European wheat and misleads farmers with pronouncements that are not supported by relevant data.
References:
1 H. Kahiluoto et al., Decline in climate resilience of European wheat. Proc. Natl. Acad. Sci. USA 116, 123–128 (2019).
2 T. Elmqvist et al., Response diversity, ecosystem change, and resilience. Front. Ecol. Environ. 1, 488–494 (2003).
3 S. De Schepper, M. De Loose, E. Van Bockstaele, P. Debergh, Ploidy analysis of azalea flower colour sports. Meded. Rijksuniv. Gent. Fak. Landbouwkd. Toegep. Biol. Wet. 66, 447–449 (2001).
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Tracing maize landraces, 50 years later
Maize is more than a crop in Mexico. While it provides food, feed and raw materials, it is also a bloodline running through the generations, connecting Mexico’s people with their past.
The fascinating diversity of maize in Mexico is rooted in its cultural and biological legacy as the center of origin of maize. Landraces, which are maize varieties that have been cultivated and subjected to selection by farmers for generations, retaining a distinct identity and lacking formal crop improvement, provide the basis of this diversity.
As with any cultural legacy, the cultivation of maize landraces can be lost with the passage of time as farmers adapt to changing markets and generational shifts take place.
Doctoral candidate Denisse McLean-Rodríguez, from the Sant’Anna School of Advanced Studies in Italy, and researchers from the International Maize and Wheat Improvement Center (CIMMYT) have undertaken a new study that traces the conservation and abandonment of maize landraces over the last 50 years in Morelos, Mexico’s second smallest state.
The study is based on a collection of 93 maize landrace samples, collected by Ángel Kato as a research assistant back in 1966-67 and stored in CIMMYT’s Maize Germplasm Bank. Researchers traced the 66 families in Morelos who donated the samples and explored the reasons why they abandoned or conserved their landraces.
Tracing landrace abandonment
In six cases, researchers were able to interview the original farmers who donated the samples to CIMMYT. In other cases, they interviewed their family members, most frequently the sons or daughters, or alternatively their grandchildren, siblings, nephews or widows.
The study reveals that maize landrace cultivation has diminished significantly within the families. Only 13 of the 66 families are still cultivating the same maize seed lots as in 1966-67 and there was consensus that the current social, economic and physical environments are unfavorable for landrace cultivation.
Among the reasons for abandonment are changes in maize cultivation technologies, shifting markets for maize and other crops, policy changes, shifting cultural preferences, urbanization and climate change.
“By finding out about landrace continuity in farmers’ fields and the factors driving change, we were able to better understand the context in which these landraces are currently cultivated,” said McLean-Rodríguez. “Our study also allowed us to evaluate the importance of ex situ conservation in facilities like CIMMYT’s Germplasm Bank.”
Maize biodiversity conservation
Maize landraces can be conserved “in situ” in farmers’ fields and “ex situ” in a protected space such as a germplasm bank or community seed bank.
“These conservation strategies are complementary,” explained McLean-Rodríguez. “Ex situ conservation helps to secure landraces in case of unpredictable conditions that threaten their conservation in the field, while in situ cultivation allows the processes that generated maize’s diversity to continue, allowing the emergence of mutations and the evolution of new potentially beneficial traits.”
The loss of landraces in farmers’ fields over 50 years emphasizes the importance of ex situ conservation. CIMMYT’s Maize Germplasm Bank holds 28,000 samples of maize and its wild relatives from 88 countries, spanning collections dating back to 1943. Safeguarded seed stored in the Germplasm Bank is protected from crises or natural disasters, and is available for breeding and research. Traits found in landraces can be incorporated into new varieties to address some of the world’s most pressing agriculture challenges like changing climates, emerging pests and disease, and malnutrition.
McLean-Rodríguez recalls an aspect of the study that she found particularly rewarding: “Many of the families who had lost their landrace for one reason or another were interested in receiving back samples of their maize from the CIMMYT Germplasm Bank. Some were interested due to personal value, while others were more interested in the productive value. They were very happy to retrieve their maize from the Germplasm Bank, and it would be very interesting to learn whether the repatriated seed is cultivated in the future.”
A family tradition
One of the families to take part in the study was farmer Roque Juarez Ramirez and his wife, Ventura Oliveros Garcia, whose father was one of the donor farmers from Morelos. “I was so happy to hear the name of my father, [Santos Oliveros],” recalls Oliveros, remembering the moment McLean-Rodríguez contacted her. “He had always been a maize farmer, as in his day they didn’t cultivate anything else. He planted on his communal village land [ejido] and he was always able to harvest a lot of maize, many ears. He planted an heirloom variety of maize that we called arribeño, or marceño, because it was always planted in March.”
Juarez senses his responsibility as a maize farmer: “I feel that the importance [of maize farming] is not small, but big. We are not talking about keeping 10 or 20 people alive; we have to feed a whole country of people who eat and drink, apart from providing for our families. We, the farmers, generate the food.”
Filling vessels of champurrado, a Mexican maize-based sweet drink, and presenting samples of the family’s staple maize — maíz colorado and the Ancho landrace — Oliveros describes what maize means to her: “Maize is very important to my family and me because it is our main source of food, for both humans and animals. We use our maize variety to make pozole, tortillas, tamales, atole, quesadillas, picadas and many other foods.”
The Juarez-Oliveros family substituted the Ancho seed lot from Olivero’s father with another seed lot from the Ancho landrace obtained from her husband’s family. The Ancho landrace is used to make pozole, and continues to be widely cultivated in some municipalities of Morelos, including Totolapan, where the family resides. However, researchers found other landraces present in the 1966-67 collection, such as Pepitilla, were harder to trace 50 years later.
The study shows that landrace abandonment is common when farming passed from one generation to the next. Older farmers were attached to their landraces and continued cultivating them, even in the face of pressing reasons to change or replace them. When the younger generations take over farm management, these landraces are often abandoned.
Nonetheless, young farmers still value the cultural and culinary importance of landraces. “Maize has an important traditional and cultural significance, and is fundamental to our economy,” said Isaac Juarez Oliveros, son of Roque and Ventura. “I have been planting [maize landraces] since I was around 15 to 20 years old. I got my maize seed from my parents. I believe it is important for families to keep planting their maize, as it has become tradition passed down through many generations.”
The legacy for future generations
Global food security depends on the maintenance of high genetic biodiversity in such key staple food crops as maize. Understanding the causes of landrace abandonment can help to develop effective landrace conservation strategies. The authors suggest that niches for landrace conservation and even expansion can be supported in the same manner that niches have been created for improved maize and other commercial crops. Meanwhile, management of genetic resources is vital, both in the field and in germplasm banks, especially in developing countries where broader diversity exists.
For Oliveros, it is a matter of family legacy: “It means a lot to me that [my family’s seed] was preserved because it has allowed my family’s maize and my father’s memory to stay alive.”
“Farmers who cultivate landraces are providing an invaluable global public service,” state the authors of the study. “It will be key to encourage maize landrace cultivation in younger farmers. Tapping into the conservation potential of the current generation of farmers is an opportunity we should not miss.”
Read the full study:
The abandonment of maize landraces over the last 50 years in Morelos, Mexico: a tracing study using a multi-level perspective
Funding for this research was provided by the CGIAR Research Program on Maize (MAIZE), the Sant’Anna School of Advanced Studies and Wageningen University.
A special acknowledgement to the families, focus group participants and municipal authorities from the state of Morelos who kindly devoted time to share their experiences with us, on the challenges and rewards of maize landrace conservation.
