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DNA Fingerprinting with a Dispersed Repeated Sequence Resolves Pathotype Diversity in the Rice Blast Fungus
M. Levy1, J. Romao, M. A. Marchetti
1Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907.
Abstract:
The poor definition of pathotype variation in the rice blast fungus has historically handicapped strategies for reducing blast disease damage to the world's rice crop. We have employed a probe for a dispersed repeated DNA sequence called MGR [Hamer et al. (1989). Proc. Natl. Acad. Sci. USA 86, 9981-9985] to construct genotype-specific, EcoRl restriction fragment length profiles (MGR-DNA fingerprints) from United States field isolates of this fungus. By using a blind-test design, we demonstrated that MGR-DNA fingerprints distinguished the major pathotypes in the United States, accurately identified the pathotypes of isolates collected over a 30-year period, and defined the organization of clonal lineages within and among pathotype groups. These results resolved a lingering controversy regarding rice blast pathotype stability and illustrated new opportunities for tracking the population dynamics and evolution of this important crop pathogen.
Insights
Understanding rice blast fungus pathotypes is crucial for crop protection. DNA fingerprinting using MGR probes accurately identified fungal strains, revealing clonal lineages and population dynamics over 30 years.
Area of Science:
- Plant Pathology
- Molecular Biology
- Mycology
Background:
- Rice blast disease, caused by the fungus Magnaporthe grisea, poses a significant threat to global rice production.
- Historically, poor definition of pathotype variation has hindered effective disease management strategies.
Purpose of the Study:
- To develop a reliable method for differentiating rice blast fungus pathotypes.
- To investigate the population structure and evolutionary dynamics of rice blast fungus isolates in the United States.
Main Methods:
- Utilized a dispersed repeated DNA sequence probe, MGR (Magnaporthe grisea repetitive element), to generate DNA fingerprints.
- Constructed genotype-specific EcoRl restriction fragment length profiles (MGR-DNA fingerprints) from United States field isolates.
- Employed a blind-test design to validate the fingerprinting method's accuracy.
Main Results:
- MGR-DNA fingerprints effectively distinguished major rice blast fungus pathotypes in the United States.
- The method accurately identified pathotypes from isolates collected over a 30-year period.
- Defined the organization of clonal lineages within and among pathotype groups, resolving controversies about pathotype stability.
Conclusions:
- MGR-DNA fingerprinting provides a robust tool for characterizing rice blast fungus populations.
- This technique offers new opportunities for tracking pathogen population dynamics and evolution.
- Improved understanding of pathotype variation can lead to more effective disease control strategies for rice.