Analysis of evidence by scientists of the International Maize and Wheat Improvement Center (CIMMYT) and CGIAR concludes that the scientific risks of genome editing are similar to those of traditional breeding: all new varieties, however developed, need to be tested for agronomic performance in a range of environments.
Social risks are mainly that these powerful technologies may be rendered inaccessible to less-commercial crops and farmers if intellectual property (IP) and regulatory policies make them expensive or difficult to use.
Genome editing has demonstrated potential to contribute to food security, improved nutrition, and value addition for farmers and consumers.
Many countries are still uncertain about whether to grow, or if and how to regulate genome-edited crop varieties. The Court of Justice of the European Union (CJEU) has stated that genome-edited crops should be considered as transgenics in the EU for regulatory purposes, a decision that could limit their use in Africa. On the other hand, several countries, including USA, Canada, Brazil, Colombia, Argentina, Chile, Kenya, Nigeria, Israel, India, and Japan have determined that genome-edited crops should not be regulated like transgenics if they do not contain foreign DNA.
Policies should enable choice and avoid the risk that genome editing technologies for crops benefit only those who can pay premium price. Smallholder farmers should have equal access to advanced technologies, should they wish to use them, as well as relevant and objective information about their value and how to use them.
In just a decade, CRISPR has become one of the most celebrated inventions in modern biology. It is swiftly changing how medical researchers study diseases: Cancer biologists are using the method to discover hidden vulnerabilities of tumor cells. Doctors are using CRISPR to edit genes that cause hereditary diseases.
But CRISPR’s influence extends far beyond medicine. Evolutionary biologists are using the technology to study Neanderthal brains and to investigate how our ape ancestors lost their tails. Plant biologists have edited seeds to produce crops with new vitamins or with the ability to withstand diseases. Some of them may reach supermarket shelves in the next few years.
Carlos Muñoz is an Research Associate – Maize Phytopathology working with CIMMYT’s Maize program.
Muñoz works on the phenotyping of the main diseases and pests that affect maize crops in Mexico with high natural incidence, and develops protocols for artificial inoculations that help identify and develop resistant maize through genetic and molecular improvement.
He is currently working on the validation of agronomic, biological and chemical management tactics to reduce mycotoxin contamination and on advising producers and technicians on the correct diagnosis of the causal agent of biotic or abiotic stresses.
Scientists examine Ug99 stem rust symptoms on wheat. (Photo: Petr Kosina/CIMMYT)
The three rust diseases, yellow (stripe) rust, black (stem) rust, and brown (left) rust occur in most wheat production environments, causing substantial yield losses and under serious epidemics, can threaten the global wheat supply.
CIMMYT is one of the largest providers of elite germplasm to national partners in over 80 countries. CIMMYT nurseries, known for research in developing adaptive, high-yielding and high-quality germplasm, also carry resistance to several biotic and abiotic stresses, such as rust disease.
Through years of research and experience, CIMMYT has found that durable control of wheat rusts can be achieved by developing and deploying wheat varieties with complex adult-plant resistance (APR). A combination of both conventional and modern technologies in APR will enable breeders to address the problem of rusts and other diseases and continue progress in delivering higher genetic gains, a key goal of the Accelerating Genetic Gains in Maize and Wheat (AGG) project.
Wheat stalks grow in a field in India. (Photo: Saad Akhtar)
For scientists, determining how best to increase wheat yields to meet food demand is a persistent challenge, particularly as the trend toward sustainably intensifying production on agricultural lands grows.
The United Nations projects that the current global population of 7.6 billion will increase to more than 9.8 billion by 2050, making higher grain yield potential vital, particularly as climate instability increases due to global warming. International efforts are also focused on meeting the Zero Hunger target detailed in the UN Sustainable Development Goals before they expire in 2030.
Now, a new landmark research survey on the grain yield potential and climate-resilience of bread wheat (Triticum aestivum L.) has brought scientists a few strides closer to meeting their ambitions.
Grain yield has traditionally been an elusive trait in genomic wheat breeding because of its quantitative genetic control, which means that it is controlled by many genomic regions with small effects.
Challenges also include a lack of good understanding about the genetic basis of grain yield, inconsistent grain yield quantitative trait loci identified in different environments, low heritability of grain yield across environments and environment interactions of grain yield.
To dissect the genetic architecture of wheat grain yield for the purposes of the research, which appeared in Scientific Reports, researchers implemented a large-scale genome-wide association study based on 100 datasets and 105,000 grain yield observations from 55,568 wheat breeding lines developed by the International Maize and Wheat Improvement Center (CIMMYT).
They evaluated the lines between 2003 and 2019 in different sites, years, planting systems, irrigation systems and abiotic stresses at CIMMYT’s primary yield testing site, the Norman E. Borlaug Experimental Research Station, Ciudad Obregon, Mexico, and in an additional eight countries — including Afghanistan, India and Myanmar — through partnerships with national programs.
The researchers also generated the grain-yield associated marker profiles and analyzed the grain-yield favorable allele frequencies for a large panel of 73,142 wheat lines, resulting in 44.5 million data points. The marker profiles indicated that the CIMMYT global wheat germplasm is rich in grain yield favorable alleles and is a trove for breeders to choose parents and design strategic crosses based on complementary grain yield alleles at desired loci.
“By dissecting the genetic basis of the elusive grain-yield trait, the resources presented in our study provide great opportunities to accelerate genomic breeding for high-yielding and climate-resilient wheat varieties, which is a major objective of the Accelerating Genetic Gain in Maize and Wheat project,” said CIMMYT wheat breeder Philomin Juliana.
“This study is unique and the largest-of-its-kind focusing on elucidating the genetic architecture of wheat grain yield,” she explained, “a highly complex and economically important trait that will have great implications on future diagnostic marker development, gene discovery, marker-assisted selection and genomic-breeding in wheat.”
Currently, crop breeding methods and agronomic management put annual productivity increases at 1.2% a year, but to ensure food security for future generations, productivity should be at 2.4% a year.
So, the extensive datasets and results presented in this study are expected to provide a framework for breeders to design effective strategies for mitigating the effects of climate change, while ensuring food-sustainability and security.
Wheat fields at Toluca station, Mexico. (Photo: Fernando Delgado/CIMMYT)
On December 11, 2020, the Nepal Agricultural Research Council (NARC) announced the release of six new wheat varieties for multiplication and distribution to the country’s wheat farmers, offering increased production for Nepal’s nearly one million wheat farmers and boosted nutrition for its 28 million wheat consumers.
The varieties, which are derived from materials developed by the International Maize and Wheat Improvement Center (CIMMYT), include five bred for elevated levels of the crucial micronutrient zinc, and Borlaug 100, a variety well known for being high yielding, drought- and heat-resilient, and resistant to wheat blast, as well as high in zinc.
“Releasing six varieties in one attempt is historic news for Nepal,” said CIMMYT Asia Regional Representative and Principal Scientist Arun Joshi.
“It is an especially impressive achievement by the NARC breeders and technicians during a time of COVID-related challenges and restrictions,” said NARC Executive Director Deepak Bhandari.
“This was a joint effort by many scientists in our team who played a critical role in generating proper data, and making a strong case for these varieties to the release committee, ” said Roshan Basnet, head of the National Wheat Research Program based in Bhairahawa, Nepal, who was instrumental in releasing three of the varieties, including Borlaug 2020.
“We are very glad that our hard work has paid off for our country’s farmers,” said Dhruba Thapa, chief and wheat breeder at NARC’s National Plant Breeding and Genetics Research Centre.
Nepal produces 1.96 million tons of wheat on more than 750,000 hectares, but its wheat farmers are mainly smallholders with less than 1-hectare holdings and limited access to inputs or mechanization. In addition, most of the popular wheat varieties grown in the country have become susceptible to new strains of wheat rust diseases.
The new varieties — Zinc Gahun 1, Zinc Gahun 2, Bheri-Ganga, Himganga, Khumal-Shakti and Borlaug 2020 — were bred and tested using a “fast-track” approach, with CIMMYT and NARC scientists moving material from trials in CIMMYT’s research station in Mexico to multiple locations in Nepal and other Target Population of Environments (TPEs) for testing.
“Thanks to a big effort from Arun Joshi and our NARC partners we were able to collect important data in first year, reducing the time it takes to release new varieties,” said CIMMYT Head of Wheat Improvement Ravi Singh.
The varieties are tailored for conditions in a range of wheat growing regions in the country — from the hotter lowland, or Terai, regions to the irrigated as well as dryer mid- and high-elevation areas — and for stresses including wheat rust diseases and wheat blast. The five high-zinc, biofortified varieties were developed through conventional crop breeding by crossing modern high yielding wheats with high zinc progenitors such as landraces, spelt wheat and emmer wheat.
“Zinc deficiency is a serious problem in Nepal, with 21% of children found to be zinc deficient in 2016,” explained said CIMMYT Senior Scientist and wheat breeder Velu Govindan, who specializes in breeding biofortified varieties. “Biofortification of staple crops such as wheat is a proven method to help reverse and prevent this deficiency, especially for those without access to a more diverse diet.”
Borlaug 2020 is equivalent to Borlaug 100, a highly prized variety released in 2014 in adbMexico to commemorate the centennial year of Nobel Peace laureate Norman E. Borlaug. Coincidently, its release in Nepal coincides with the 50th anniversary of Borlaug’s Nobel Peace Prize.
NARC staff have already begun the process of seed multiplication and conducting participatory varietal selection trials with farmers, so very soon farmers throughout the country will benefit from these seeds.
“The number of new varieties and record release time is amazing,” said Joshi. “We now have varieties that will help Nepal’s farmers well into the future.”
CIMMYT breeding of biofortified varieties was funded by HarvestPlus. Variety release and seed multiplication activities in Nepal were supported by NARC and the Asian Development Bank (ADB) through collaboration with ADB Natural Resources Principal & Agriculture Specialist Michiko Katagami. This NARC-ADB-CIMMYT collaboration was prompted by World Food Prize winner and former HarvestPlus CEO Howarth Bouis, and provided crucial support that enabled the release in a record time.
The International Maize and Wheat Improvement Center (CIMMYT) is the global leader in publicly-funded maize and wheat research and related farming systems. Headquartered near Mexico City, CIMMYT works with hundreds of partners throughout the developing world to sustainably increase the productivity of maize and wheat cropping systems, thus improving global food security and reducing poverty. CIMMYT is a member of the CGIAR System and leads the CGIAR Research Programs on Maize and Wheat and the Excellence in Breeding Platform. The Center receives support from national governments, foundations, development banks and other public and private agencies. For more information, visit staging.cimmyt.org.
ABOUT NARC:
Nepal Agricultural Research Council (NARC) was established in 1991 as an autonomous organization under Nepal Agricultural Research Council Act – 1991 to conduct agricultural research in the country to uplift the economic level of Nepalese people.
ABOUT ADB:
The Asian Development Bank (ADB) is committed to achieving a prosperous, inclusive, resilient, and sustainable Asia and the Pacific, while sustaining its efforts to eradicate extreme poverty. It assists its members and partners by providing loans, technical assistance, grants, and equity investments to promote social and economic development.
Alberto Chassaigne has 27 years of experience working in maize seed systems, maize breeding, agronomy and farmer outreach. Since February 2022, he is the Maize Germplasm Bank Curator focusing on the conservation, access to and benefit sharing of the enhanced use of germplasm. As a Maize Seed Systems Specialist, he works focusing primarily on promoting commercial seed production and enhanced adoption of maize hybrids and OPV, developing seed production research, capacity building and scaling production from Breeder Seed to Certified Seed. Since 2013 he has served 73 seed companies and registered 95 CIMMYT varieties in Mexico, and advised the public and private sector in Haiti, Colombia and Peru.Chassaigne holds a PhD in Seed Production from Colegio de Postgraduados, Mexico, a PhD in Agricultural Science and an MSc. in Agronomy from the Central University of Venezuela, and an additional degree in Agricultural Engineer.
Thokozile Ndhlela is a maize line development breeder with CIMMYT’s Global Maize Program, based in Zimbabwe. Her work mainly involves breeding for stress tolerant and nutritious maize varieties to boost food and nutrition security, especially in developing countries.
Akshaya Biswal is a scientist specialized in plant transformation and tissue culture, working with CIMMYT’s Genetic Resources Program. His current work focuses on application of gene editing to improve host-plant resistance.
CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)/Cas9-mediated genome editing has revolutionized our ability to study gene function and alter it to improve biotic and abiotic stress tolerance, increase yield potential of crop plants or even to improve the quality of grains. Various plant diseases cause up to 30% yield loss in cereals. Polyploidy in maize and wheat poses additional difficulty to breeders for developing and deploying resistant lines to pathogens. Some these can be solved by biotechnological intervention with relative ease. Biswal’s team uses gene editing to: control Maize Lethal Necrosis (MLN) in Africa for improved grain harvests; improve stem rust and powdery mildew resistance in wheat; and discover and validate the function of candidate genes underpinning large effect QTLs.
Prior to joining CIMMYT, Biswal completed postdoctoral placements at the International Rice Research Institute (IRRI) and the University of North Carolina. He earned a PhD in Biotechnology at Jawaharlal Technological University, an MSc from Banaras Hindu University, and a BSc from Utkal University, India.
Dagne Wegary works as maize breeder, mainly focusing on the development and deployment of high yielding, and abiotic and abiotic stress-tolerant maize varieties for resource-poor farmers in eastern and southern Africa. He is coordinating multi-location on-station regional variety trials that are conducted in collaboration with NARS and seed companies in eastern and southern Africa.
Before moving to Zimbabwe in 2019, Wegary worked as CIMMYT’s maize seed systems specialist based in Ethiopia. During this period, he contributed to the release of several maize varieties, production and distribution of early generation seeds of selected varieties, which boosted maize production and productivity in the country. He is also actively involved in technical capacity building of NARS and seed company partners.
Global wheat production is currently facing great challenges, from increasing climate variation to occurrence of various pests and diseases. These factors continue to limit wheat production in a number of countries, including China, where in 2018 unseasonably cold temperatures resulted in yield reduction of more than 10% in major wheat growing regions. Around the same time, Fusarium head blight spread from the Yangtze region to the Yellow and Huai Valleys, and northern China experienced a shortage of irrigated water.
In light of these ongoing challenges, international collaboration, as well as the development of new technologies and their integration with existing ones, has a key role to play in supporting sustainable wheat improvement, especially in developing countries. The International Maize and Wheat Improvement Center (CIMMYT) has been collaborating with China on wheat improvement for over 40 years, driving significant progress in a number of areas.
Notably, a standardized protocol for testing Chinese noodle quality has been established, as has a methodology for breeding adult-plant resistance to yellow rust, leaf rust and powdery mildew. More than 330 cultivars derived from CIMMYT germplasm have been released in the country and are currently grown over 9% of the Chinese wheat production area, while physiological approaches have been used to characterize yield potential and develop high-efficiency phenotyping platforms. The development of climate-resilient cultivars using new technology will be a priority area for future collaboration.
In a special issue of Frontiers of Agricultural Science and Engineering focused on wheat genetics and breeding, CIMMYT researchers present highlights from global progress in wheat genomics, breeding for disease resistance, as well as quality improvement, in a collection of nine review articles and one research article. They emphasize the significance of using new technology for genotyping and phenotyping when developing new cultivars, as well as the importance of global collaboration in responding to ongoing challenges.
In a paper on wheat stem rust, CIMMYT scientists Sridhar Bhavani, David Hodson, Julio Huerta-Espino, Mandeep Randawa and Ravi Singh discuss progress in breeding for resistance to Ug99 and other races of stem rust fungus, complex virulence combinations of which continue to pose a significant threat to global wheat production. The authors detail how effective gene stewardship and new generation breeding materials, complemented by active surveillance and monitoring, have helped to limit major epidemics and increase grain yield potential in key target environments.
In the same issue, an article by Caiyun Lui et al. discusses the application of spectral reflectance indices (SRIs) as proxies to screen for yield potential and heat stress, which is emerging in crop breeding programs. The results of a recent study, which evaluated 287 elite lines, highlight the utility of SRIs as proxies for grain yield. High heritability estimates and the identification of marker-trait associations indicate that SRIs are useful tools for understanding the genetic basis of agronomic and physiological traits.
Modeling Genotype × Environment Interaction Using a Factor Analytic Model of On-Farm Wheat Trials in the Yaqui Valley of Mexico. 2019. Vargas-Hernández, M., Ortiz-Monasterio, I., Perez-Rodriguez, P., Montesinos-Lopez, O.A., Montesinos-Lopez, A., Burgueño, J., Crossa, J. In: Agronomy Journal v. 111, no. 1, p. 1-11.
Guillermo Garcia Barrios, a co-author of the study and student at Colegio de Postgraduados in Montecillo, Mexico, with a PHERAstar machine used to validate genetic markers. (Photo: Marcia MacNeil/CIMMYT)
To meet the demand for wheat from a rising and quickly urbanizing population, wheat yields in farmers’ fields must increase by an estimated 1.5% each year through 2030.
Of all the factors that influence yield, grain weight is the trait that is most stable and heritable for use in breeding improved wheat varieties. Breeders measure this by thousand grain weight (TGW).
Over the years, molecular scientists have made efforts to identify genes related to increased TGW, in order to speed up breeding through marker-assisted selection (MAS). Using MAS, breeders can select parents that contain genes related to the traits they are looking for, increasing the likelihood they will be passed on and incorporated in a new variety.
There have been some limited successes in these efforts: in the past years, a few genes related to increased TGW have been cloned, and a set of genetic markers have been determined to be used for MAS. However, the effects of most of these candidate genes have not yet been validated in diverse sets of wheat germplasm throughout the world that represent the full range of global wheat growing environments.
A group of wheat geneticists and molecular breeders from the International Maize and Wheat Improvement Center (CIMMYT) has recently conducted a thorough study to confirm the effects of the favorable alleles reported for these genes on TGW in CIMMYT wheat, and to identify new genetic determinants of this desired trait.
They found some good news and some bad news.
First, the good news: focusing on more than 4,000 lines of CIMMYT wheat germplasm they found 15 haplotype blocks significantly associated with TGW. Four haplotype blocks associated with TGW were also associated with grain yield — a grand prize for breeders, because in general the positive association of grain yield with TGW is less profound and sometimes even negative. However, of the 14 genes that had been previously reported to increase TGW, only one in CIMMYT’s 2015-2016 Elite Yield Trial and two in Wheat Associative Mapping Initiative panel were shown to have significant TGW associations.
Wheat grains prepared for placement in a Thousand Grain Weight machine. (Photo: Marcia MacNeil/CIMMYT)
The scientists also found that the alleles — pairs of genes on a chromosome that determine heredity — that were supposedly favorable to TGW actually decreased it. These candidate genes also appear to vary in their TGW effects with genetic background and/or environment.
Thus, these findings also provide a foundation for more detailed investigations, opening the door for more studies on the genetic background dependence and environment sensitivity of the known candidate genes for TGW.
“Our findings indicate that it will be challenging to use MAS based on these existing markers across individual breeding programs,” said Deepmala Sehgal, CIMMYT wheat geneticist and the primary author of the study.
However, efforts to identify new genetic determinants of TGW were promising. The authors’ study of CIMMYT germplasm found one locus on chromosome 6A that showed increases of up to 2.60 grams in TGW and up to 258 kilograms per hectare in grain yield.
Thousand Grain Weight is measured in this machine at CIMMYT’s global headquarters in Texcoco, Mexico. (Photo: Marcia MacNeil/CIMMYT)
This discovery expands opportunities for developing diagnostic markers to assist in multi-gene pyramiding — a process that can derive new and complementary allele combinations for enhanced wheat TGW and grain yield.
Most of all, the study highlights the strong need for better and more validation of the genes related to this and other traits, so that breeders can be sure they are using material that is confirmed to increase wheat grain weight and genetic yield.
“Our findings are very promising for future efforts to efficiently develop more productive wheat in both grain weight and grain yield,” said Sehgal. “This ultimately means more bread on household tables throughout the world.”
“Validation of Candidate Gene-Based Markers and Identification of Novel Loci for Thousand-Grain Weight in Spring Bread Wheat” in Frontiers in Plant Science by Deepmala Sehgal, Suchismita Mondal, Carlos Guzman, Guillermo Garcia Barrios, Carolina Franco, Ravi Singh and Susanne Dreisigacker was supported by funding from the CGIAR Research Program on Wheat (WHEAT), the Delivering Genetic Gain in Wheat (DGGW) project funded by the Bill & Melinda Gates Foundation and the UK Department for International Development (DFID), and the US Agency for International Development (USAID) Feed the Future Innovation Lab for Applied Wheat Genomics.
