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<p>Downy mildew disease causes up to 100% yield loss in cucumbers, and there are only a few resistant sources available globally. To identify and characterize resistance sources, 328 cucumber genotypes were evaluated under natural epiphytotic conditions to determine sources of downy mildew resistance and to investigate the role of antioxidant enzymes in conferring resistance. Based on field and artificial screening, three genotypes IC-572024 and IC-527400, PI-197086 were identified as resistant, while other lines showed variable degree of susceptibility. Ten representative genotypes including resistant and susceptible lines were selected for detailed biochemical analysis. Comparative studies revealed significantly higher total phenolic content in resistant lines, particularly upon pathogen challenge, in contrast to the decline observed in susceptible ones. Activities of key antioxidant enzymes including peroxidase (POD), polyphenol oxidase (PPO), catalase (CAT), superoxide dismutase (SOD), and phenylalanine ammonia-lyase (PAL) were significantly high in resistant genotypes. Notably, PAL activity showed the highest induction in IC-527400 (76.43%), followed by IC-572024 (71.37%) and PI-197086 (65.33%). A strong negative correlation was observed between percent disease index (PDI) and activities of SOD (<i>r</i> = − 0.871**), POD (<i>r</i> = − 0.772**), total phenol content (TPC, <i>r</i> = − 0.771**), and PPO (<i>r</i> = − 0.702*), underscoring the importance of these biochemical traits in disease resistance. The findings indicate that enhanced antioxidant enzyme activity and phenolic accumulation are key components of the defense response in cucumber, contributing to differential resistance against downy mildew. These understandings will help in better management of this disease in cucumber and aid in marker-assisted breeding.</p>

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Correlation of enhanced antioxidant enzyme activity and phenolic content with downy mildew resistance in cucumber (Cucumis sativus L.)

  • 期刊论文

  • 发表日期：

    2026年3月30日

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  • Rahul Kumar,
  • Vidya Sagar,
  • Dharm Pal Singh,
  • Pragya,
  • Sudhakar Pandey,
  • Rajeev Kumar,
  • Jyoti Devi,
  • Nakul Gupta,
  • Shailesh Kumar Tiwari,
  • Nagendra Rai,
  • Rajesh Kumar

摘要

Downy mildew disease causes up to 100% yield loss in cucumbers, and there are only a few resistant sources available globally. To identify and characterize resistance sources, 328 cucumber genotypes were evaluated under natural epiphytotic conditions to determine sources of downy mildew resistance and to investigate the role of antioxidant enzymes in conferring resistance. Based on field and artificial screening, three genotypes IC-572024 and IC-527400, PI-197086 were identified as resistant, while other lines showed variable degree of susceptibility. Ten representative genotypes including resistant and susceptible lines were selected for detailed biochemical analysis. Comparative studies revealed significantly higher total phenolic content in resistant lines, particularly upon pathogen challenge, in contrast to the decline observed in susceptible ones. Activities of key antioxidant enzymes including peroxidase (POD), polyphenol oxidase (PPO), catalase (CAT), superoxide dismutase (SOD), and phenylalanine ammonia-lyase (PAL) were significantly high in resistant genotypes. Notably, PAL activity showed the highest induction in IC-527400 (76.43%), followed by IC-572024 (71.37%) and PI-197086 (65.33%). A strong negative correlation was observed between percent disease index (PDI) and activities of SOD (r = − 0.871**), POD (r = − 0.772**), total phenol content (TPC, r = − 0.771**), and PPO (r = − 0.702*), underscoring the importance of these biochemical traits in disease resistance. The findings indicate that enhanced antioxidant enzyme activity and phenolic accumulation are key components of the defense response in cucumber, contributing to differential resistance against downy mildew. These understandings will help in better management of this disease in cucumber and aid in marker-assisted breeding.