Long-term blast control in high eating quality rice using multilines.

Area of Science:

• Agricultural Science
• Plant Pathology
• Genetics

Background:

• Genetic heterogeneity and crop homogeneity offer dual benefits for disease control and harvest quality.
• Rice multilines, mixtures of genetically uniform plants, can suppress disease while maintaining quality.
• Practical, large-scale commercial methods for multiline deployment are needed.

Purpose of the Study:

• To develop and evaluate an effective rice multiline management strategy.
• To assess the impact of monitoring virulent blast races on disease control.
• To implement a practical system for commercial multiline use over large geographical areas.

Main Methods:

• Conversion of the elite Koshihikari rice cultivar into a multiline (Koshihikari BL - blast resistant lines).
• Large-scale planting of Koshihikari BL across 94,000 hectares in Niigata Prefecture, Japan.
• Monitoring of virulent rice blast races to inform seed mixture composition changes.

Main Results:

• Significant reduction in rice blast severity: 79.4% in leaves and 81.8% in panicles (2005-2019 vs. 2004).
• Two-thirds reduction in fungicide application after the introduction of Koshihikari BL.
• Demonstrated long-term disease control through seed mixture diversification and resistant line rotation.

Conclusions:

• Effective rice multiline management is achievable through adaptive seed mixture strategies.
• Monitoring pathogen populations is crucial for sustaining disease resistance in multiline systems.
• Diversification and rotation of resistant lines prevent virulent race evolution, ensuring durable disease control.