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Baseline sensitivity and characteristics of florylpicoxamid resistant mutants in Magnaporthe oryzae
Guangda Shao1, Ziwei Xue1, Bangzhi Luo1
1State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, College of Plant Protection, Northwest A&F University, Yangling 712100, Shaanxi, China.
Abstract:
Rice blast, a highly important disease affecting rice production, is caused by Magnaporthe oryzae. The growth of this pathogen is, however, strongly inhibited by the novel quinone inside inhibitor (QiI) fungicide florylpicoxamid. This study investigated the risk and mechanism of resistance to florylpicoxamid in M. oryzae. The baseline sensitivity of isolated M. oryzae strains (n = 101) to florylpicoxamid was established, with an average EC50 (concentration inhibiting 50 % of mycelial growth) of 0.0213 ± 0.0186 μg/mL. The wild-type strains were then subjected to florylpicoxamid adaptation to generate six stable florylpicoxamid-resistant mutants with resistance factors above 100, but all mutants displayed significantly lower fitness compared with their parental isolates. We speculated that the risk of M. oryzae developing resistance to florylpicoxamid is moderate. Molecular docking analyses further suggested that the A37V amino acid substitution in MoCytb reduced florylpicoxamid's binding affinity to MoCytb, thus confirming that this mutation conferred florylpicoxamid resistance in M. oryzae. These results provide new insights into QiI fungicide resistance mechanisms and may guide future applications of florylpicoxamid in managing rice blast.
Insights
The fungicide florylpicoxamid effectively controls rice blast disease caused by Magnaporthe oryzae. However, resistance may develop through specific mutations in the MoCytb gene, posing a moderate risk to its long-term efficacy.
Area of Science:
- Plant Pathology
- Fungicide Resistance
- Molecular Biology
Background:
- Rice blast, caused by Magnaporthe oryzae, is a major threat to global rice production.
- The novel quinone inside inhibitor (QiI) fungicide florylpicoxamid shows high efficacy against M. oryzae.
- Understanding resistance mechanisms is crucial for sustainable disease management.
Purpose of the Study:
- To investigate the risk and molecular mechanisms of florylpicoxamid resistance in Magnaporthe oryzae.
- To establish baseline sensitivity of M. oryzae to florylpicoxamid.
- To identify genetic mutations conferring resistance.
Main Methods:
- Collected and tested 101 M. oryzae isolates for baseline sensitivity to florylpicoxamid.
- Generated stable resistant mutants through in vitro adaptation.
- Utilized molecular docking to analyze the impact of mutations on fungicide binding.
Main Results:
- Established a low average EC50 of 0.0213 μg/mL for florylpicoxamid against M. oryzae.
- Developed six resistant mutants with resistance factors >100, but exhibiting reduced fitness.
- Identified the A37V substitution in MoCytb as a key mutation reducing florylpicoxamid binding affinity.
Conclusions:
- The risk of M. oryzae developing resistance to florylpicoxamid is assessed as moderate.
- The A37V mutation in MoCytb confers resistance by decreasing fungicide binding.
- Findings offer insights into QiI fungicide resistance and inform florylpicoxamid application strategies for rice blast control.
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