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<p>Blast disease caused by <i>Magnaporthe</i> spp. is one of the most destructive diseases affecting graminaceous hosts such as rice and millet crops worldwide. Understanding the reproductive biology and the genetic structure of the pathogen is essential for devising effective management strategies. The current study aimed to assess the mating type distribution, fertility status, DNA polymorphism, gene flow and the population structure of <i>Magnaporthe</i> spp. infecting millets and rice across major blast hotspots of India. Mating type-specific PCR amplification of 136 isolates targeting <i>MAT1-1</i> and <i>MAT1-2</i> idiomorphs revealed diverse reproductive strategies. Among the millet-infecting isolates (<i>n</i> = 127), 36.22% were male fertile, 26.77% female fertile, 17.32% hermaphroditic and 19.68% unknown. Rice infecting isolates displayed a mixed mating profile, while bajra isolates were unknown. The presence of both mating types and hermaphroditism suggests potential for sexual recombination, posing a risk of increased genetic variability and virulence. The sequence-based polymorphism analysis of 114 isolates (from finger and foxtail millet) revealed 187 segregating sites and 208 mutations, including 117 singleton sites. The population exhibited high Hd (0.982) and moderate nucleotide diversity (π = 0.0053), indicating significant genetic richness and potential for adaptive evolution. Neutrality tests Tajima’s D (-2.418), Fu and Li’s D* (-5.197), and F* (-4.752) were significantly negative (<i>p</i> &lt; 0.02) supporting recent population expansion or purifying selection. Population differentiation analyses showed low Gst (0.0217), moderate Fst (0.0797) with high gene flow (Nm = 11.27) reflecting limited population subdivision with ongoing genetic exchange. Haplotype network analysis identified 95 unique haplotypes with most being singletons, supporting high mutational diversity. A central haplotype (Hap_39), comprising 15 isolates of different mating types represents a potential ancestral or broadly adapted lineage. Interestingly, hermaphroditic isolates predominantly clustered in a distinct clade suggesting reproductive isolation and host-specific evolutionary trajectories. AMOVA revealed that 93.27% of genetic variation existed within populations and 6.73% among populations (Φ<sub>ST</sub> = 0.067) reinforcing the conclusion of a predominantly panmictic structure with localized differentiation. Findings of this study provides novel insights into the mating type dynamics and genetic diversity of <i>Magnaporthe</i> spp. infecting millets and rice in India, emphasizing the evolutionary potential of this pathogen and the need for vigilant monitoring and resistant cultivar deployment.</p>

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Deciphering mating type and population genetic landscape of Magnaporthe population adapted to millets and rice in blast hotspots of India

  • 期刊论文

  • 发表日期：

    2025年7月15日

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  • K. B. Palanna,
  • Gutha Venkata Ramesh,
  • Prasanna S. Koti,
  • H. D. Vinaykumar,
  • Divya Bhandhari,
  • H. R. Raveendra,
  • T. S. S. K. Patro,
  • T. V. Krishna,
  • T. E. Nagaraja,
  • R. Madhusudhana,
  • C. Tara Satyavathi

摘要

Blast disease caused by Magnaporthe spp. is one of the most destructive diseases affecting graminaceous hosts such as rice and millet crops worldwide. Understanding the reproductive biology and the genetic structure of the pathogen is essential for devising effective management strategies. The current study aimed to assess the mating type distribution, fertility status, DNA polymorphism, gene flow and the population structure of Magnaporthe spp. infecting millets and rice across major blast hotspots of India. Mating type-specific PCR amplification of 136 isolates targeting MAT1-1 and MAT1-2 idiomorphs revealed diverse reproductive strategies. Among the millet-infecting isolates (n = 127), 36.22% were male fertile, 26.77% female fertile, 17.32% hermaphroditic and 19.68% unknown. Rice infecting isolates displayed a mixed mating profile, while bajra isolates were unknown. The presence of both mating types and hermaphroditism suggests potential for sexual recombination, posing a risk of increased genetic variability and virulence. The sequence-based polymorphism analysis of 114 isolates (from finger and foxtail millet) revealed 187 segregating sites and 208 mutations, including 117 singleton sites. The population exhibited high Hd (0.982) and moderate nucleotide diversity (π = 0.0053), indicating significant genetic richness and potential for adaptive evolution. Neutrality tests Tajima’s D (-2.418), Fu and Li’s D* (-5.197), and F* (-4.752) were significantly negative (p < 0.02) supporting recent population expansion or purifying selection. Population differentiation analyses showed low Gst (0.0217), moderate Fst (0.0797) with high gene flow (Nm = 11.27) reflecting limited population subdivision with ongoing genetic exchange. Haplotype network analysis identified 95 unique haplotypes with most being singletons, supporting high mutational diversity. A central haplotype (Hap_39), comprising 15 isolates of different mating types represents a potential ancestral or broadly adapted lineage. Interestingly, hermaphroditic isolates predominantly clustered in a distinct clade suggesting reproductive isolation and host-specific evolutionary trajectories. AMOVA revealed that 93.27% of genetic variation existed within populations and 6.73% among populations (ΦST = 0.067) reinforcing the conclusion of a predominantly panmictic structure with localized differentiation. Findings of this study provides novel insights into the mating type dynamics and genetic diversity of Magnaporthe spp. infecting millets and rice in India, emphasizing the evolutionary potential of this pathogen and the need for vigilant monitoring and resistant cultivar deployment.