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Published on: August 4, 2018
Three point-mutations in cytochrome b confer resistance to trifloxystrobin in Magnaporthe oryzae
Jianqiang Miao1, Guosen Zhao1, Bin Wang2,3
1State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Yangling, China.
Background:
Rice blast, caused by Magnaporthe oryzae, is the most devastating disease in rice. Recently, trifloxystrobin was registered for the control of M. oryzae in China. The resistance profile and mechanism of M. oryzae to trifloxystrobin were investigated in the present study, providing important data for the recommended use of trifloxystrobin.
Results:
The baseline sensitivity was established at a half maximal effective concentration (EC50 ) of 0.024 μg mL-1 . Nine stable trifloxystrobin-resistant mutants were generated with EC50 values ranging from 12.75 to 171.49 μg mL-1 . The mutants exhibited strong adaptive traits in sporulation, conidial germination, and pathogenicity. Positive cross-resistance was only observed between trifloxystrobin and azoxystrobin, but not between trifloxystrobin and carbendazim, isoprothiolane, prochloraz, or chlorothalonil. The point mutation G143S in cytochrome b (cyt b) protein was found in eight high-resistance mutants with resistant factor ranging from 2295.16 to 13 200.00; and the double mutation G137R/M296V only occurred in Mg117-1 with resistance factor ≈ 900. The G143S mutation weakened hydrogen bond interactions, and G137R/M296V changed the conformation of trifloxystrobin in the cyt b binding pocket. A molecular detection method was established for the rapid detection of G143S mutants in M. oryzae.
Conclusion:
The resistance risk of M. oryzae to trifloxystrobin could be moderate to high. Two genotypes with three point-mutations G143S, G137R, and M296V conferred resistance to trifloxystrobin in M. oryzae. © 2020 Society of Chemical Industry.
Insights
Magnaporthe oryzae resistance to trifloxystrobin poses a moderate to high risk for rice blast control. Key mutations in the cytochrome b protein, specifically G143S, confer significant resistance, necessitating molecular detection methods.
Area of Science:
- Plant Pathology
- Fungal Genetics
- Agricultural Chemistry
Background:
- Rice blast, caused by Magnaporthe oryzae, is a major threat to global rice production.
- Trifloxystrobin is a fungicide recently registered for controlling M. oryzae in China.
Purpose of the Study:
- To investigate the resistance profile and underlying mechanisms of M. oryzae to trifloxystrobin.
- To provide crucial data for the judicious application of trifloxystrobin in rice cultivation.
Main Methods:
- Generation and characterization of trifloxystrobin-resistant M. oryzae mutants.
- Determination of baseline sensitivity (EC50) and cross-resistance patterns.
- Identification of genetic mutations (G143S, G137R, M296V) in the cytochrome b gene.
- Development of a molecular detection method for resistant mutants.
Main Results:
- Established baseline EC50 for trifloxystrobin sensitivity (0.024 μg/mL).
- Generated nine resistant mutants with EC50 values up to 171.49 μg/mL, showing enhanced sporulation, germination, and pathogenicity.
- Identified G143S mutation in eight mutants and G137R/M296V double mutation in one, correlating with high resistance.
- Observed cross-resistance only between trifloxystrobin and azoxystrobin.
- Developed a molecular assay for detecting G143S mutants.
Conclusions:
- M. oryzae exhibits a moderate to high resistance risk to trifloxystrobin.
- Specific point mutations (G143S, G137R, M296V) in the cytochrome b gene are responsible for trifloxystrobin resistance.
- The findings support the need for resistance management strategies and molecular monitoring.
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