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funder_partner: Swedish Research Council (Vetenskapsrådet)

Building global capacity to combat wheat blast

Researchers and experts from 15 countries convened in Zambia, between 4-15 March 2024, for an international training on wheat blast disease screening, surveillance, and management.

Wheat blast, caused by pathogen Magnaporthe oryzae pathotype triticum, is threatening global wheat production especially in warmer and humid regions. The disease was first observed in Parana state of Brazil in 1985 and subsequently spread to Bolivia, Paraguay, and Argentina. Outside of South America, wheat blast incidences were recorded for the first time in Bangladesh in 2016 and in Zambian wheat fields in 2018.

To mitigate the impact of this potential plant pandemic, the Zambia Agriculture Research Institute (ZARI), in collaboration with CIMMYT and other partners, organized a comprehensive training for building research capacity and raising awareness within the local and international community, especially in at-risk countries.

“This collaborative effort, supported by various international partners and funders, underscores the importance of global cooperation in addressing agricultural challenges such as wheat blast. The objective of the training was to empower researchers with knowledge and tools for enhanced wheat production resilience in regions vulnerable to this destructive disease,” said Pawan Kumar Singh, principal scientist and project leader at CIMMYT. Singh collaborated with Batiseba Tembo, wheat breeder at ZARI-Zambia, to coordinate and lead the training program.

Thirty-eight wheat scientists, researchers, professors, policymakers, and extension agents from countries including Bangladesh, Brazil, Ethiopia, India, Kenya, Mexico, Nepal, South Africa, Sweden, Tanzania, United Kingdom, Uruguay, Zambia, and Zimbabwe convened at the Mt. Makulu Central Research Station in Chilanga, Zambia.

“Wheat blast is a devastating disease that requires concerted efforts to effectively manage it and halt further spread. The disease is new to Africa, so developing capacity amongst country partners before the disease spreads more widely is critical,” said Tembo.

Participants at the International Training on Wheat Blast Screening and Surveillance. (Photo: CIMMYT)

Highlights from the training: discussions, lab exercises, and field visits

During the training, participants engaged in lectures, laboratory exercises, and field visits. There were insightful discussions on key topics including the fundamentals of wheat blast epidemiology, disease identification, molecular detection of the wheat blast pathogen, isolation and preservation techniques for the pathogen, disease scoring methods, disease management strategies, and field surveillance and monitoring.

The course also provided practical experience in disease evaluation at the Precision Phenotyping Platform (PPP) screening nursery located in Chilanga research station. This involved characterization of a diverse range of wheat germplasm with the aim of releasing resistant varieties in countries vulnerable to wheat blast. Additionally, participants undertook field visits to farmers’ fields, conducting surveillance of wheat blast-infected areas. They collected samples and recorded survey data using electronic open data kit (ODK) capture tools.

Participants listen to a lecture by B.N. Verma, director of Zambia Seed Co., on the history of wheat production in Zambia. (Photo: CIMMYT)

“The killer disease needs to be understood and managed utilizing multi-faceted approaches to limit the expansion and damages it can cause to global wheat production. The Bangladesh Wheat and Maize Research Institute (BWMRI) is willing to share all the strategies it deployed to mitigate the effect of wheat blast,” said Golam Faruq, BWMRI’s director general.

Participants visited seed farms to gain practical insights into seed production processes and quality assurance measures. These visits provided first-hand knowledge of seed selection, breeding techniques, and management practices crucial for developing resistant wheat varieties. Participants also visited research sites and laboratories to observe advanced research methodologies and technologies related to wheat blast management. These visits exposed them to cutting-edge techniques in disease diagnosis, molecular analysis, and germplasm screening, enhancing their understanding of effective disease surveillance and control strategies.

Field visit. (Photo: CIMMYT)

“The training and knowledge sharing event was a significant first step in developing understanding and capacity to deal with wheat blast for partners from several African countries. It was wonderful to see the efforts made to ensure gender diversity among participants,” said Professor Diane Saunders from the John Innes Centre, UK.

CIMMYT and BWMRI host international training program on surveillance and management strategies for wheat blast

The devastating disease wheat blast is a threat to crop production in many South Asian countries. In Bangladesh, it was first identified in seven southern and southwestern districts in 2016, and later spread to 27 others causing significant damage. The International Maize and Wheat Improvement Center (CIMMYT) is working with the Bangladesh Wheat and Maize Research Institute (BWMRI) and other national partners to conduct research and extension activities to mitigate the ongoing threat.

From March 1-10, 2023, a group of 46 wheat researchers, government extension agents, and policy makers from ten countries — Bangladesh, Brazil, China, Ethiopia, India, Japan, Mexico, Nepal, Sweden, and Zambia — gathered in Jashore, Bangladesh to learn about and exchange experiences regarding various wheat diseases, particularly wheat blast. Following the COVID-19 pandemic, this was the first in-person international wheat blast training held in Bangladesh. It focused on the practical application of key and tricky elements of disease surveillance and management strategies, such as resistance breeding and integrated disease management.

Training participants get hands-on practice using a field microscope, Bangladesh. (Photo: Ridoy/CIMMYT)

“This is an excellent training program,” said Shaikh Mohammad Bokhtiar, executive chairman of the Bangladesh Agriculture Research Council (BARC), during the opening session.  “Participants will learn how to reduce the severity of the blast disease, develop and expand blast resistant varieties to farmers, increase production, and reduce imports.”

This sentiment was echoed by Golam Faruq, director general of BWMRI. “This program helps in the identification of blast-resistant lines from across the globe,” he said. “From this training, participants will learn to manage the devastating blast disease in their own countries and include these learnings into their national programs.”

Hands-on training

The training was divided into three sections: lectures by national and international scientists; laboratory and field experiment visits; and trips to farmers’ fields. Through the lecture series, participants learned about a variety of topics including disease identification, molecular detection, host-pathogen interaction, epidemiology and integrated disease management.

Hands-on activities were linked to working on the Precision Phenotyping Platform (PPP), which involves the characterization of more than 4,000 wheat germplasm and releasing several resistant varieties in countries vulnerable to wheat blast. Participants practiced taking heading notes, identifying field disease symptoms, tagging, and scoring disease. They conducted disease surveillance in farmers’ fields in Meherpur and Faridpur districts — both of which are extremely prone to wheat blast — observing the disease, collecting samples and GPS coordinates, and completing surveillance forms.

Muhammad Rezaul Kabir, senior wheat breeder at BWMRI, explains the Precision Phenotyping Platform, Bangladesh. (Photo: Md. Harun-Or-Rashid/CIMMYT)

Participants learned how to use cutting-edge technology to recognize blast lesions in leaves using field microscopes. They went to a pre-installed spore trapping system in a farmer’s field to learn about the equipment and steps for collecting spore samples, observing them under a compound microscope, and counting spores. They also visited the certified seed production fields of Shawdesh Seed, a local company which has played an important role in promoting wheat blast resistant varieties BARI Gom 33 and BWMRI Gom 3 regionally, and Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU) in Gazipur to see current wheat blast research in action.

Blast-resistance in Bangladesh

“I am so happy to see the excellent infrastructure and work ethics of staff that has made possible good science and impactful research come out of the PPP,” said Aakash Chawade, associate professor in Plant Breeding at the Swedish University of Agricultural Sciences. “Rapid development of blast-resistant varieties and their dissemination will help Bangladesh mitigate the effects of wheat blast, not only inside the country but by supporting neighboring ones as well.”

Training participants scout and score disease in a blast-infected wheat field, Bangladesh. (Photo: Md. Harun-Or-Rashid/CIMMYT)

“Besides the biotic and abiotic challenges faced in wheat production, climate change and the Russia-Ukraine crisis are further creating limitations to wheat production and marketing,” said Pawan Kumar Singh, head of Wheat Pathology at CIMMYT and lead organizer of the training. “Due to the development of blast-resistant wheat varieties and its commercial production under integrated disease management practices, the domestic production of wheat in Bangladesh has increased and there is increased interest from farmers in wheat.”

Dave Hodson, a principal scientist at CIMMYT and one of the training’s resource speakers, added: “This is a remarkable success that researchers developed two blast resistant varieties in Bangladesh urgently. It was only achievable because of the correct measures taken by the researchers and support of Government policies.”

However, there are still some barriers to widespread adoption of these varieties. As such, in parallel to other activities, a team from Bangladesh Agricultural University (BAU) joined the field trip to meet local farmers and conduct research into the socio-economic factors influencing the adoption and scaling of relevant wheat varieties.

The Australian High Commission, ACIAR and BARC delegates recognizes the BWMRI-CIMMYT collaborative wheat blast research platform in Bangladesh

Delegates with other officials in front of the seminar room. (Photo: Biswajit/BWMRI)

Representatives from Australian Centre for International Agricultural Research (ACIAR) and Bangladesh Agricultural Research Council (BARC) paid a visit to Bangladesh to see the valuable work of the Precision Phenotyping Platform (PPP).

PPP was established in response to the devastating wheat blast disease, which was first reported in the country in 2016.

Technical and financial support from the International Maize and Wheat Improvement Center (CIMMYT), the Australian Commission for International Agricultural Research and the Australian Centre for International Agricultural Research, along with other funders, has contributed to the effort to combat the disease.

This is achieved by generating precise data for wheat blast resistance in germplasm in Bangladesh, as well as other wheat growing countries. This PPP has been used to screen elite lines and genetic resources from various countries.

On February 16 and 17, 2023, two groups of national and international delegations visited the BWMRI-CIMMYT collaborative research platform PPP at the BWMRI regional station in Jashore, Bangladesh.

The first group was made up of representatives from both the Australian Commission for International Agricultural Research and the Australian Centre for International Agricultural Research. This included seven commissioners under the direction of Fiona Simson, along with ACIAR senior officials from Australia and India.

The other group was from BARC, which was led by Executive Chairman Shaikh Mohammad Bokhtiar, along with Golam Faruq, Director General of BWMRI, and Andrew Sharpe, Bangabandhu Research Chair, Global Institute of Food Security (GIFS), University of Saskatchewan in Canada.

Both delegations were welcomed by Muhammad Rezaul Kabir, the Senior Wheat Breeder at BWMRI. Kabir gave a brief presentation about the platform and other wheat blast collaborative research programs in the seminar room.

The delegations then went to the PPP field, where BWMRI researchers Kabir and Robiul Islam, as well as CIMMYT researcher Md. Harun-Or-Rashid, explained further information about the BWMRI-CIMMYT collaborative research. Both commissioners and delegates appreciated seeing the work being conducted in person by the national and international collaborations of BWMRI and CIMMYT on wheat blast research.

Visitors observing blast disease symptoms in wheat leaves. (Photo: Muhammad Rezaul Kabir/BWMRI)

“It is important, innovative work, that is affecting not only Bangladesh but many countries around the world that are now starting to be concerned about the impacts of wheat blast,” commissioner Simson said. “This study is very important for Australia and we are pleased to be contributing to it.”

Lindsay Falvey, another commissioner, added, “This is a wonderful experiment, using high-level science and technologies to combat wheat blast in Bangladesh. The experiment is well-planned. Overall, it is an excellent platform.”

ACIAR delegate Eric Huttner added to the praise for the project. “The platform is performing extremely well for the purpose of evaluating lines, resistance to the disease and that’s very useful for Bangladesh and rest of the world,” he said. “This is a gift that Bangladesh is giving to the neighboring countries to protect wheat.”

The delegates pledged to share their expert advice with the Minister of Foreign Affairs in Bangladesh in order to increase investments and improve facilities for agricultural research programs in the country.

Golam Faruq, Director General of BWMRI discussing the PPP with Shaikh Mohammad Bokhtiar, Executive Chairman of BARC (Photo: Md. Harun-Or-Rashid/CIMMYT)

“This is an excellent work,” Executive Chairman of BARC, Bokhtiar said. “We can get more information from screening activities by using bioinformatics tools and training people through the BARC-GIFS program.”

Pawan Kumar Singh, Head of Wheat Pathology at CIMMYT-Mexico and Project Leader, coordinated the visits virtually and expressed his thanks to the delegations for their visit to the platform. This PPP, within a short span of few years, has been highly impactful, characterizing more than 15,000 entries and releasing several resistant varieties in countries vulnerable to wheat blast.

Greenhouse upgrades at BWMRI for wheat blast research

Md. Sayedul Islam inaugurated the greenhouse complex along with Golam Faruq and Md. Benojir Alam. (Credit: Timothy J. Krupnik/CIMMYT)

A new greenhouse complex, built with financial support from the International Maize and Wheat Improvement Center (CIMMYT), at the Bangladesh Wheat and Maize Research Institute (BWMRI) was inaugurated on 13 August 2022. The greenhouse was built at BWMRI’s headquarters in Dinajpur, Bangladesh.

This complex has a room for generator, a sample preparation room and space for a small laboratory. These upgrades will add new momentum for greenhouse activities and BWMRI and CIMMYT scientists designed the facility to accommodate wheat scientists from Bangladesh and other countries.

The BWMRI has been working to combat wheat blast disease since 2016, with financial and technical support from CIMMYT and other investors. CIMMYT has also assisted the Government of Bangladesh in developing an early warning system for wheat blast.

Because of the challenging phenology of synthetic wheat and introductions from winter and facultative wheat zones, field condition evaluation of these germplasm is difficult and the greenhouse will help ease this hurdle. Additionally, several pathological experiments investigating the biology of wheat blast will now be able to be performed in the new greenhouse facility.

Supplementary activities at the greenhouse include disease screening and research into unlocking the genetics of host resistance. The installation of a diesel generator will keep the greenhouse running in case of power outages.

Visitors to the newly constructed greenhouse at the Bangladesh Wheat and Maize Research Institute. (Credit: Rezaul Kabir/BWMRI)

Md. Sayedul Islam, Secretary of the Ministry of Agriculture, inaugurated the greenhouse complex. Additional attendees at the opening included Shaikh Mohammad Bokhtiar, Executive Chairman of the Bangladesh Agricultural Research Council (BARC), Golam Faruq, Director General of BWMRI, Mirza Mofazzal Islam, Director General of the Bangladesh Institute of Nuclear Agriculture (BINA), Debasish Sarker, Director General of the Bangladesh Agricultural Research Institute (BARI), Md. Benojir Alam, Director General of the Department of Agricultural Extension (DAE), and Md. Abdul Wadud, Executive Director and Additional Secretary at the Bangladesh Institute of Research and Training on Applied Nutrition (BIRTAN). Timothy J. Krupnik, country representative of CIMMYT in Bangladesh, was also present.

New publications: Genome-wide breeding to curtail wheat blast

A recent publication in the journal Frontiers of Plant Science provides results of the first-ever study to test genomic selection in breeding for resistance to wheat blast, a deadly disease caused by the fungus Magnaporthe oryzae that is spreading from its origin in Brazil to threaten wheat crops in South Asia and sub-Saharan Africa.

Genomic selection identifies individual plants based on the information from molecular markers, DNA signposts for genes of interest, that are distributed densely throughout the wheat genome. For wheat blast, the results can help predict which wheat lines hold promise as providers of blast resistance for future crosses and those that can be advanced to the next generation after selection.

In this study, scientists from the International Maize and Wheat Improvement Center (CIMMYT) and partners evaluated genomic selection by combining genotypic data with extensive and precise field data on wheat blast responses for three sets of genetically diverse wheat lines and varieties, more than 700 in all, grown by partners at locations in Bangladesh and Bolivia over several crop cycles.

The study also compared the use of a small number of molecular markers linked to the 2NS translocation, a chromosome segment from the grass species Aegilops ventricosa that was introduced into wheat in the 1980s and is a strong and stable source of blast resistance, with predictions using thousands of genome-wide markers. The outcome confirms that, in environments where wheat blast resistance is determined by the 2NS translocation, genotyping using one-to-few markers tagging the translocation is enough to predict the blast response of wheat lines.

Finally, the authors found that selection based on a few wheat blast-associated molecular markers retained 89% of lines that were also selected using field performance data, and discarded 92% of those that were discarded based on field performance data. Thus, both marker-assisted selection and genomic selection offer viable alternatives to the slower and more expensive field screening of many thousands of wheat lines in hot-spot locations for the disease, particularly at early stages of breeding, and can speed the development of blast-resistant wheat varieties.

Read the full study:
Genomic Selection for Wheat Blast in a Diversity Panel, Breeding Panel and Full-Sibs Panel

The research was conducted by scientists from the International Maize and Wheat Improvement Center (CIMMYT), the Bangladesh Wheat and Maize Research Institute (BWMRI), the Instituto Nacional de Innovación Agropecuaria y Forestal (INIAF) of Bolivia, the Borlaug Institute for South Asia (BISA) and the Indian Council of Agricultural Research (ICAR) in India, the Swedish University of Agricultural Sciences (Alnarp), and Kansas State University in the USA. Funding for the study was provided by the Bill & Melinda Gates Foundation, the Foreign and Commonwealth Development Office of the United Kingdom, the U.S. Agency for International Development (USAID), the CGIAR Research Program on Wheat (WHEAT), the Indian Council of Agricultural Research (ICAR), the Swedish Research Council, and the Australian Centre for International Agricultural Research (ACIAR).

Cover photo: A researcher from Bangladesh shows blast infected wheat spikes and explains how the disease directly attacks the grain. (Photo: Chris Knight/Cornell University)

Taming wheat blast

As wheat blast continues to infect crops in  countries around the world, researchers are seeking ways to stop its spread. The disease — caused by the Magnaporthe oryzae pathotype Triticum — can dramatically reduce crop yields, and hinder food and economic security in the regions in which it has taken hold.

Researchers from the International Maize and Wheat Improvement Center (CIMMYT) and other international institutions looked into the potential for wheat blast to spread, and surveys existing tactics used to combat it. According to them, a combination of methods — including using and promoting resistant varieties, using fungicides, and deploying strategic agricultural practices — has the best chance to stem the disease.

The disease was originally identified in Brazil in 1985. Since then, it has spread to several other countries in South America, including Argentina, Bolivia and Paraguay. During the 1990s, wheat blast impacted as many as three million hectares in the region. It continues to pose a threat.

Through international grain trade, wheat blast was introduced to Bangladesh in 2016. The disease has impacted around 15,000 hectares of land in the country and reduced average yields by as much as 51% in infected fields.

Because the fungus’ spores can travel on the wind, it could spread to neighboring countries, such as China, India, Nepal and Pakistan — countries in which wheat provides food and jobs for billions of people. The disease can also spread to other locales via international trade, as was the case in Bangladesh.

“The disease, in the first three decades, was spreading slowly, but in the last four or five years its pace has picked up and made two intercontinental jumps,” said Pawan Singh, CIMMYT’s head of wheat pathology, and one of the authors of the recent paper.

In the last four decades, wheat blast has appeared in South America, Asia an Africa. (Video: Alfonso Cortés/CIMMYT)

The good fight

Infected seeds are the most likely vector when it comes to the disease spreading over long distances, like onto other continents. As such, one of the key wheat blast mitigation strategies is in the hands of the world’s governments. The paper recommends quarantining potentially infected grain and seeds before they enter a new jurisdiction.

Governments can also create wheat “holidays”, which functionally ban cultivation of wheat in farms near regions where the disease has taken hold. Ideally, this would keep infectable crops out of the reach of wheat blast’s airborne and wind-flung spores. In 2017, India banned wheat cultivation within five kilometers of Bangladesh’s border, for instance. The paper also recommends that other crops — such as legumes and oilseed — that cannot be infected by the wheat blast pathogen be grown in these areas instead, to protect the farmers’ livelihoods.

Other tactics involve partnerships between researchers and agricultural workers. For instance, early warning systems for wheat blast prediction have been developed and are being implemented in Bangladesh and Brazil. Using weather data, these systems alert farmers when the conditions are ideal for a wheat blast outbreak.

Researchers are also hunting for wheat varieties that are resistant to the disease. Currently, no varieties are fully immune, but a few do show promise and can partially resist the ailment depending upon the disease pressure. Many of these resistant varieties have the CIMMYT genotype Milan in their pedigree.

“But the resistance is still limited. It is still quite narrow, basically one single gene,” Xinyao He, one of the co-authors of the paper said, adding that identifying new resistant genes and incorporating them into breeding programs could help reduce wheat blast’s impact.

Wheat spikes damaged by wheat blast. (Photo: Xinyao He/CIMMYT)
Wheat spikes damaged by wheat blast. (Photo: Xinyao He/CIMMYT)

The more the merrier

Other methods outlined in the paper directly involve farmers. However, some of these might be more economically or practically feasible than others, particularly for small-scale farmers in developing countries. Wheat blast thrives in warm, humid climates, so farmers can adjust their planting date so the wheat flowers when the weather is drier and cooler. This method is relatively easy and low-cost.

The research also recommends that farmers rotate crops, alternating between wheat and other plants wheat blast cannot infect, so the disease will not carry over from one year to the next. Farmers should also destroy or remove crop residues, which may contain wheat blast spores. Adding various minerals to the soil, such as silicon, magnesium, and calcium, can also help the plants fend off the fungus. Another option is induced resistance, applying chemicals to the plants such as jasmonic acid and ethylene that trigger its natural resistance, much like a vaccine, Singh said.

Currently, fungicide use, including the treatment of seeds with the compounds, is common practice to protect crops from wheat blast. While this has proven to be somewhat effective, it adds additional costs which can be hard for small-scale farmers to swallow. Furthermore, the pathogen evolves to survive these fungicides. As the fungus changes, it can also gain the ability to overcome resistant crop varieties. The paper notes that rotating fungicides or developing new ones — as well as identifying and deploying more resistant genes within the wheat — can help address this issue.

However, combining some of these efforts in tandem could have a marked benefit in the fight against wheat blast. For instance, according to Singh, using resistant wheat varieties, fungicides, and quarantine measures together could be a time-, labor-, and cost-effective way for small-scale farmers in developing nations to safeguard their crops and livelihoods.

“Multiple approaches need to be taken to manage wheat blast,” he said.

Scientists find genomic regions associated with wheat blast resistance in CIMMYT nurseries

Wheat spike damaged by wheat blast.
Wheat blast damages wheat spikes. (Photo: Xinyao He / CIMMYT)

In an article published in Nature Scientific Reports, a team of scientists led by wheat breeder Philomin Juliana from the International Wheat and Maize Improvement Center (CIMMYT) conducted a large genome-wide association study to look for genomic regions that could also be associated with resistance to wheat blast.

Juliana and fellow scientists found 36 significant markers on chromosome 2AS, 3BL, 4AL and 7BL that appeared to be consistently associated with blast resistance across different environments. Among these, 20 markers were found to be in the position of the 2NS translocation, a chromosomal segment transferred to wheat from a wild relative, Aegilops ventricosa, that has very strong and effective resistance to wheat blast.

The team also gained excellent insights into the blast resistance of the globally-distributed CIMMYT germplasm by genomic fingerprinting a panel over 4,000 wheat lines for the presence of the 2NS translocation, and found that it was present in 94.1% of lines from International Bread Wheat Screening Nurseries (IBWSNs) and 93.7% of lines from Semi-Arid Wheat Screening Nurseries (SAWSNs). Although it is reassuring that such a high percentage of CIMMYT wheat lines already have the 2NS translocation and implied blast resistance, finding other novel resistance genes will be instrumental in building widespread, global resilience to wheat blast outbreaks in the long-term.

The researchers used data collected over the last two years from CIMMYT’s IBWSNs and SAWSNs by collaborators at the Bangladesh Wheat and Maize Research Institute (BWMRI) and Bolivia’s Instituto Nacional de Innovación Agropecuaria y Forestal (INIAF).

Devastating fungal disease

Wheat blast, caused by the fungus Magnaporthe oryzae pathotype Triticum, was first identified in 1985 in South America, but has been seen in Bangladesh in recent years. The expansion of the disease is a great concern for regions of similar environmental conditions in South Asia, and other regions globally.

Although management of the disease using fungicide is possible, it is not completely effective for multiple reasons, including inefficiency during high disease pressure, resistance of the fungal populations to some classes of fungicides, and the affordability of fungicide to resource-poor farmers. Scientists see the development and deployment of wheat with genetic resistance to blast as the most sustainable and farmer-friendly approach to preventing devastating outbreaks around the world.

This work was made possible by the generous support of the Delivering Genetic Gains in Wheat (DGGW) project funded by the Bill & Melinda Gates Foundation, the U.K. Foreign, Commonwealth & Development Office (FCDO) and managed by Cornell University, the U.S. Agency for International Development’s Feed the Future initiative, the CGIAR Research Program on Wheat (WHEAT), the Indian Council of Agricultural Research (ICAR), The Swedish Research Council (Vetenskapsråd), and the Australian Centre for International Agricultural Research (ACIAR).

Read the full article:
Genome‑wide association mapping for wheat blast resistance in CIMMYT’s international screening nurseries evaluated in Bolivia and Bangladesh

This story was originally posted on the website of the CGIAR Research Program on Wheat (wheat.org).

Wheat blast has made the intercontinental jump to Africa

Scientists observe wheat blast in Zambia's Mpika district. (Photo: Batiseba Tembo/ZARI)
Scientists observe wheat blast in Zambia’s Mpika district. (Photo: Batiseba Tembo/ZARI)

Wheat blast, a fast-acting and devastating fungal disease, has been reported for the first time on the African continent. In an article published in the scientific journal PLoS One, a team of scientists confirmed that symptoms of wheat blast first appeared in Zambia during the 2018 rainy season, in experimental plots and small-scale farms in the Mpika district, Muchinga province.

Researchers from the International Maize and Wheat Improvement Center (CIMMYT), the US Department of Agriculture – Foreign Disease Weed Science Research Unit (USDA-ARS) and the Zambian Agricultural Research Institute (ZARI) participated in this study.

Wheat blast poses a serious threat to rain-fed wheat production in Zambia and raises the alarm for surrounding regions and countries on the African continent with similar environmental conditions. Worldwide, 2.5 billion consumers depend on wheat as a staple food and, in recent years, several African countries have been actively working towards reducing dependence on wheat imports.

“This presents yet another challenging biotic constraint to rain-fed wheat production in Zambia,” said Batiseba Tembo, wheat breeder at ZARI and lead scientist on the study.

A difficult diagnosis

Researchers from ZARI check for wheat blast in experimental plots. (Photo: Batiseba Tembo/ZARI)
Researchers from ZARI check for wheat blast in experimental plots. (Photo: Batiseba Tembo/ZARI)

“The first occurrence of the disease was very distressing. This happened at the spike stage, and caused significant losses,” Tembo said. “Nothing of this nature has happened before in Zambia.”

Researchers were initially confused when symptoms of the disease were first reported in the fields of Mpika. Zambia has unique agro-climatic conditions, particularly in the rainfed wheat production system, and diseases such as spot blotch and Fusarium head blight are common.

“The crop had silvery white spikes and a green canopy, resulting in shriveled grains or no grains at all… Within the span of seven days, a whole field can be attacked,” Tembo explained. Samples were collected and analyzed in the ZARI laboratory, and suspicions grew among researchers that this may be a new disease entirely.

Tembo participated in the Basic Wheat Improvement Course at CIMMYT’s global headquarters in Mexico, where she discussed the new disease with Pawan Singh, head of Wheat Pathology at CIMMYT. Singh worked with Tembo to provide guidance and the molecular markers needed for the sample analysis in Zambia, and coordinated the analysis of the wheat disease samples at the USDA-ARS facility in Fort Detrick, Maryland, United States.

All experiments confirmed the presence of the fungus Magnaporthe oryzae pathotype Triticum (MoT), which causes the disease.

“This is a disaster which needs immediate attention,” Tembo said. “Otherwise, wheat blast has the potential to marginalize the growth of rain-fed wheat production in Zambia and may threaten wheat production in neighboring countries as well.”

Wheat blast spreads through infected seeds and crop residues, as well as by spores that can travel long distances in the air. The spread of blast within Zambia is indicated by both mechanisms of expansion.

Wheat blast has expanded rapidly since it was initially discovered in Brazil in 1985. (Map: Kai Sonder/CIMMYT)
Wheat blast has expanded rapidly since it was initially discovered in Brazil in 1985. (Map: Kai Sonder/CIMMYT)

A cause for innovation and collaboration

CIMMYT and the CGIAR Research Program on Wheat (WHEAT) are taking action on several fronts to combat wheat blast. Trainings and international courses invite participants to gain new technical skills and knowledge in blast diagnostics, treatment and mitigation strategies. WHEAT scientists and partners are also studying the genetic factors that increase resistance to the disease and developing early warning systems.

“A set of research outcomes, including the development of resistant varieties, identification of effective fungicides, agronomic measures, and new findings in the epidemiology of disease development will be helpful in mitigating wheat blast in Zambia,” Singh said.

“It is imperative that the regional and global scientific communities join hands to determine effective measures to halt further spread of this worrisome disease in Zambia and beyond,” Tembo expressed.


Read the study:

Detection and characterization of fungus (Magnaporthe oryzae pathotype Triticum) causing wheat blast disease on rain-fed grown wheat (Triticum aestivum L.) in Zambia

Interview opportunities:

Pawan Kumar Singh, Senior Scientist and Head of Wheat Pathology, International Maize and Wheat Improvement Center (CIMMYT)

Batiseba Tembo, Wheat Breeder, Zambian Agricultural Research Institute (ZARI)

For more information, or to arrange interviews, contact the media team:

Rodrigo Ordóñez, Communications Manager, CIMMYT. r.ordonez@cgiar.org

Acknowledgements

Financial support for this research was provided by the Zambia Agriculture Research Institute (ZARI), the CGIAR Research Program on Wheat (WHEAT), the Australian Centre for International Agricultural Research (ACIAR), and the US Department of Agriculture’s Agricultural Research Service (USDA-ARS). 

The Basic Wheat Training Program and Wheat Blast Training is made possible by support from investors including the Australian Centre for International Agricultural Research (ACIAR), WHEAT, the Indian Council of Agricultural Research (ICAR), Krishi Gobeshona Foundation (KGF), the Swedish Research Council (SRC) and the United States Agency for International Development (USAID).

The Accelerating Genetic Gains in Maize and Wheat (AGG) project is funded by the Bill & Melinda Gates Foundation, the UK Foreign, Commonwealth & Development Office, the United States Agency for International Development and the Foundation for Food and Agricultural Research (FFAR).

About CIMMYT

The International Maize and What 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 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.

What is wheat blast?

What is wheat blast disease?

Wheat blast is a fast-acting and devastating fungal disease that threatens food safety and security in tropical areas in South America and South Asia. Directly striking the wheat ear, wheat blast can shrivel and deform the grain in less than a week from the first symptoms, leaving farmers no time to act.

The disease, caused by the fungus Magnaporthe oryzae pathotype triticum (MoT), can spread through infected seeds and survives on crop residues, as well as by spores that can travel long distances in the air.

Magnaporthe oryzae can infect many grasses, including barley, lolium, rice, and wheat, but specific isolates of this pathogen generally infect limited species; that is, wheat isolates infect preferably wheat plants but can use several more cereal and grass species as alternate hosts. The Bangladesh wheat blast isolate is being studied to determine its host range. The Magnaporthe oryzae genome is well-studied but major gaps remain in knowledge about its epidemiology.

The pathogen can infect all aerial wheat plant parts, but maximum damage is done when it infects the wheat ear. It can shrivel and deform the grain in less than a week from first symptoms, leaving farmers no time to act.
The pathogen can infect all aerial wheat plant parts, but maximum damage is done when it infects the wheat ear. It can shrivel and deform the grain in less than a week from first symptoms, leaving farmers no time to act.

Where is wheat blast found?

First officially identified in Brazil in 1985, the disease is widespread in South American wheat fields, affecting as much as 3 million hectares in the early 1990s. It continues to seriously threaten the potential for wheat cropping in the region.

In 2016, wheat blast spread to Bangladesh, which suffered a severe outbreak. It has impacted around 15,000 hectares of land in eight districts, reducing yield on average by as much as 51% in the affected fields.

Wheat-producing countries and presence of wheat blast.
Wheat-producing countries and presence of wheat blast.

How does blast infect a wheat crop?

Wheat blast spreads through infected seeds, crop residues as well as by spores that can travel long distances in the air.

Blast appears sporadically on wheat and grows well on numerous other plants and crops, so rotations do not control it. The irregular frequency of outbreaks also makes it hard to understand or predict the precise conditions for disease development, or to methodically select resistant wheat lines.

At present blast requires concurrent heat and humidity to develop and is confined to areas with those conditions. However, crop fungi are known to mutate and adapt to new conditions, which should be considered in management efforts.

How can farmers prevent and manage wheat blast?

There are no widely available resistant varieties, and fungicides are expensive and provide only a partial defense. They are also often hard to obtain or use in the regions where blast occurs, and must be applied well before any symptoms appear — a prohibitive expense for many farmers.

The Magnaporthe oryzae fungus is physiologically and genetically complex, so even after more than three decades, scientists do not fully understand how it interacts with wheat or which genes in wheat confer durable resistance.

Researchers from the International Maize and Wheat Improvement Center (CIMMYT) are partnering with national researchers and meteorological agencies on ways to work towards solutions to mitigate the threat of wheat blast and increase the resilience of smallholder farmers in the region. Through the USAID-supported Cereal Systems Initiative for South Asia (CSISA) and Climate Services for Resilient Development (CSRD) projects, CIMMYT and its partners are developing agronomic methods and early warning systems so farmers can prepare for and reduce the impact of wheat blast.

CIMMYT works in a global collaboration to mitigate the threat of wheat blast, funded by the Australian Centre for International Agricultural Research (ACIAR), the CGIAR Research Program on Wheat (WHEAT), the Indian Council of Agricultural Research (ICAR) and the Swedish Research Council (Vetenskapsrådet). Some of the partners who collaborate include the Bangladesh Wheat and Maize Research Institute (BWMRI), Bolivia’s Instituto Nacional de Innovación Agropecuaria y Forestal (INIAF), Kansas State University and the Agricultural Research Service of the US (USDA-ARS).