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<p>Sunflower (<i>Helianthus annuus</i> L.), a key oilseed crop, suffers significant yield losses due to foliar diseases, particularly Alternaria leaf blight. Understanding the variability of <i>Alternaria</i> spp. is critical for effective disease management and resistance breeding. This study evaluated 20 <i>Alternaria</i> isolates collected from diverse sunflower-growing regions for their cultural, morphological, molecular, and pathogenic variability. Isolates exhibited notable differences in colony morphology, conidial size, septation, and sporulation on PDA medium. Molecular characterization using ITS, EF-1α, and AhN1 primers identified species including <i>A. helianthi</i>, <i>A. alternata</i>, <i>A. helianthiinficiens</i>, <i>A. longipes</i>, <i>A. tenuissima</i>, <i>A. macrospora</i>, <i>A. alternata</i> f. sp. <i>mali</i>, and <i>A. brassicicola</i>. Phylogenetic analysis grouped these into two major clades with three subclusters. Pathogenicity assays on six sunflower genotypes revealed significant virulence variability. Isolates DhaAl-9 (<i>A. helianthi</i>) and GadAl-1 (<i>Alternaria alternata</i>) demonstrated the highest virulence indices, while HaoAl-19 (<i>A. brassicicola</i>) and BenAl-15 (<i>A. alternata</i> f. sp. <i>mali</i>) were least virulent. Among genotypes, RSFH 1887 exhibited strong resistance, whereas CMS 519B was most susceptible. A strong correlation between greenhouse virulence indices and field disease severity was observed. The results underscore substantial genetic and pathogenic diversity within <i>Alternaria</i> spp. populations, emphasizing the need to incorporate multiple virulence sources in breeding programs and to tailor region-specific management strategies for sustainable sunflower production.</p>

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From genes to virulence, a tale of many faces: untangling the pathogen puzzle, a multi-dimensional assessment of Alternaria spp. infecting sunflower for bridging pathogen diversity and host resistance

  • 期刊论文

  • 发表日期：

    2026年7月1日

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  • Ajith C. R.,
  • Sudheendra A. Ashtaputre,
  • Laxminarayan Rao M. S.,
  • Ramraddi N. Madalli,
  • Basavaraj K.,
  • Mangesh Dudhe Y.,
  • Uma M. S.,
  • Vijayakumar A. Giritammannavar,
  • Milind P. Potdar

摘要

Sunflower (Helianthus annuus L.), a key oilseed crop, suffers significant yield losses due to foliar diseases, particularly Alternaria leaf blight. Understanding the variability of Alternaria spp. is critical for effective disease management and resistance breeding. This study evaluated 20 Alternaria isolates collected from diverse sunflower-growing regions for their cultural, morphological, molecular, and pathogenic variability. Isolates exhibited notable differences in colony morphology, conidial size, septation, and sporulation on PDA medium. Molecular characterization using ITS, EF-1α, and AhN1 primers identified species including A. helianthi, A. alternata, A. helianthiinficiens, A. longipes, A. tenuissima, A. macrospora, A. alternata f. sp. mali, and A. brassicicola. Phylogenetic analysis grouped these into two major clades with three subclusters. Pathogenicity assays on six sunflower genotypes revealed significant virulence variability. Isolates DhaAl-9 (A. helianthi) and GadAl-1 (Alternaria alternata) demonstrated the highest virulence indices, while HaoAl-19 (A. brassicicola) and BenAl-15 (A. alternata f. sp. mali) were least virulent. Among genotypes, RSFH 1887 exhibited strong resistance, whereas CMS 519B was most susceptible. A strong correlation between greenhouse virulence indices and field disease severity was observed. The results underscore substantial genetic and pathogenic diversity within Alternaria spp. populations, emphasizing the need to incorporate multiple virulence sources in breeding programs and to tailor region-specific management strategies for sustainable sunflower production.