International Collaborative Research for the Implementation and Dissemination of a Differential System of Rice Blast

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Attribution—The original work must be clearly credited. Suggested citation: Obara, M., Saito, H., & Kobayashi, N., (2026) International collaborative research for the implementation and dissemination of a differential system of rice blast. Green Asia Report Series, No. 11. Japan International Research Center for Agricultural Sciences (JIRCAS), Japan. License: CC BY 4.0.
https://doi.org/10.64096/gars-e.11
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Abstract: v
1: Introduction: 1
2: Overview of the Differential System for Blast Pathogen Virulence and Resistance: 2
2.1: Discovery of Blast Pathogen Virulence and Resistance Breakdown: 2
2.2: Disease Control Technologies Utilizing Resistance Genes: 2
2.3: Utilization of Partial Resistance Genes: 3
2.4: Need for an International Differential System: 3
2.5: Establishment of an International Differential System: 4
2.6: Application of the International Differential System: 5
3: Case Study 1 – Dynamics of Rice Blast Pathogen Virulence in Vietnam: 7
3.1: Background: 7
3.2: Methods: 8
1) Isolation and Inoculation of Blast Pathogens: 8
2) Virulence Evaluation Using the Differential System: 8
3) Hierarchical Clustering: 9
4) Geospatial Data Analysis: 9
3.3: Results and Discussion: 9
1) Temporal and Regional Distribution Analysis: 9
2) Identification of Resistance Breakdown Factor in Thien Uu 8: 11
4: Case Study 2 – Resistance Characteristics of Introgression lines in Vietnam: 12
4.1: Background: 12
4.2: Complete Resistance Genes in Introgression lines Carrying Pb1 and/or pi21: 12
4.3: Agronomic Traits of Introgression Lines Carrying Pb1 and/or pi21: 13
4.4: Response to Vietnamese Standard Differential Blast Isolates (SDBIs): 13
4.5: Response of the Introgression Lines to Vietnamese Isolates Infecting TU8: 14
4.6: Pesticide Reduction Trials Using the introgression Lines: 16
5: Case Study 3 – Pesticide Reduction Trials in Bangladesh: 17
5.1: Background: 17
5.2: Partial Resistance of Introgression lines: 17
5.3: Reduced chemical pesticide use in fields with the introgression lines: 18
6: Future Directions and Methodologies for Social Implementation: 20
6.1: Accelerating Technology Dissemination through Farmer Demonstrations: 20
6.2: Breeding Strategies and Pathogen Monitoring for Sustainable Blast Resistance: 21
6.3: Breeding for Blast Resistance and Multi‐Disease Resistance: 22
Authors contribution statement: 23
Acknowledgement: 23
References: 23
Appendix 1.1: 25
Appendix 4.1. Development of Introgression lines with Partial Resistance Genes: 26
Appendix 4.2. Cultivation and Agronomic Evaluation of the Introgression lines: 27
Appendix 4.3. Yield and Related Traits of Thien Uu 8 (TU8) and Introgression lines in Spring 2023 (Hanoi and Ha Nam): 28
Appendix 5.1. Introgression lines with Blast Resistance and Pesticide Reduction Trial Design in Bangladesh: 29

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Abstract

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Rice blast, caused by Magnaporthe oryzae is one of the most devastating diseases affecting rice production in the Asia-Monsoon region, with estimated global yield losses ranging from 10% to 30%. Introducing resistant varieties is a promising strategy to simultaneously decrease environmental impact and improve sustainable productivity. However, the breakdown of resistance owing to pathogen evolution is a recurring issue. In the context of sustainable rice production in the Asia-Monsoon region, establishing an international collaboration system that enables the consistent evaluation of blast pathogen virulence across the region is essential, as it facilitates the identification of resistance traits in rice genetic resources, and tracks regional pathogen dynamics.
This report introduces the concept of differential system for blast resistance and international deployment of a blast differential system via collaborative research between JIRCAS and IRRI. Subsequently, this report presents case studies of applying the Differential System in Vietnam and Bangladesh under the Green Asia Project, aligned with Japan’s “Strategy for Sustainable Food Systems, MIDORI.” The case studies include the analysis of long-term monitoring data on the dynamics of rice blast pathogen virulence in Vietnam, field assessment of the resistance of introgression lines in Vietnam, and validation of pesticide reduction using introgression lines with partial resistance genes in field trials conducted in Bangladesh.
These results indicate that the effectiveness of resistance genes significantly differs by location and time, highlighting the criticality of continuous surveillance and strategic gene combinations, whereas introgression lines introducing resistance genes (Pb1 and pi21) showed broader and more durable resistance compared to the original variety and the potential for pesticide reduction without considerable yield loss via resistant variety adoption.
These results support key policy goals such as decreasing environmental burdens, enhancing disease management efficiency, and optimizing pesticide use. Accelerating technology dissemination through farmer demonstrations and strengthening breeding strategies and pathogen monitoring systems are necessary for the development of sustainable blast management. This report provides practical insights into rice blast management and contributes to the realization of sustainable rice production in the Asia-Monsoon region.

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Japan International Research Center for Agricultural Sciences

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eng

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http://purl.org/coar/resource_type/c_18ws

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research report

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http://purl.org/coar/version/c_970fb48d4fbd8a85

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10.64096/gars-e.11

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2026-03-27 06:22:30.524479

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