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<p>Pathogen invasion, particularly by fungal agents such as <i>Fusarium fujikuroi</i>, activates systemic acquired resistance in plants, a defense mechanism closely associated with elevated level of salicylic acid. This study examines the efficacy of salicylic acid in modulating enzyme activity and expression of defense-related genes (<i>PR1</i>, <i>PR3</i>, <i>PR4</i>, and <i>PAL</i>) in the sensitive rice cultivar Tarom during <i>F. fujikuroi</i> infection<i>.</i> Rice seedlings were pretreated with 200 ppm salicylic acid before pathogen inoculation, and samples were collected at 24, 48, 72, and 96 h post-inoculation for both control and pretreated plants. Morphological traits, including plant height, root length, plant weight, and disease severity index, were measured following a randomized complete design with three replications. Furthermore, Molecular and Biochemical analysis was performed in triplicate for all samples, and results were statistically analyzed using the Student’s t-test. Evaluation of antifungal activity of salicylic acid showed that pretreatment of this component significantly reduced the Disease Severity Index from 71% in untreated plants to 35.4% in salicylic acid<b>-</b>pretreated plants. Additionally, shoot length and fresh weight were markedly increased in the pretreated plants compared to the untreated plants. Molecular analysis revealed enhanced expression of <i>PAL</i>, <i>PR1</i>, <i>PR3</i>, and <i>PR4</i> genes, peaking at 72 h post-inoculation, 6.12, 3.5, 2.6 and 11.9 fold of S0F1 respectively, and gradually declining by 96 h. Biochemical assays confirmed elevated peroxidase enzyme activity levels in salicylic acid-treated plants; in contrast, the activity of catalase, and ascorbate peroxidase enzymes, and the accumulation level of malondialdehyde decreased in pretreated plants. These findings indicate that <i>NPR1</i> was activated through increasing in <i>PAL</i>, which in turn amplifies <i>PR</i> gene expression, effectively triggering SAR. In conclusion, salicylic acid application effectively strengthens rice plant resistance against infection by enhancing defense genes and antioxidant enzyme activity and offering a promising, eco-friendly strategy for managing bakanae disease.</p>

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Salicylic Acid Induces Resistance to Bakanae Disease in Oryza sativa

  • 期刊论文

  • 发表日期：

    2025年11月10日

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  • Mohammad Taheri Saffar,
  • Leila Ahangar,
  • Fakhtak Taliei

摘要

Pathogen invasion, particularly by fungal agents such as Fusarium fujikuroi, activates systemic acquired resistance in plants, a defense mechanism closely associated with elevated level of salicylic acid. This study examines the efficacy of salicylic acid in modulating enzyme activity and expression of defense-related genes (PR1, PR3, PR4, and PAL) in the sensitive rice cultivar Tarom during F. fujikuroi infection. Rice seedlings were pretreated with 200 ppm salicylic acid before pathogen inoculation, and samples were collected at 24, 48, 72, and 96 h post-inoculation for both control and pretreated plants. Morphological traits, including plant height, root length, plant weight, and disease severity index, were measured following a randomized complete design with three replications. Furthermore, Molecular and Biochemical analysis was performed in triplicate for all samples, and results were statistically analyzed using the Student’s t-test. Evaluation of antifungal activity of salicylic acid showed that pretreatment of this component significantly reduced the Disease Severity Index from 71% in untreated plants to 35.4% in salicylic acid-pretreated plants. Additionally, shoot length and fresh weight were markedly increased in the pretreated plants compared to the untreated plants. Molecular analysis revealed enhanced expression of PAL, PR1, PR3, and PR4 genes, peaking at 72 h post-inoculation, 6.12, 3.5, 2.6 and 11.9 fold of S0F1 respectively, and gradually declining by 96 h. Biochemical assays confirmed elevated peroxidase enzyme activity levels in salicylic acid-treated plants; in contrast, the activity of catalase, and ascorbate peroxidase enzymes, and the accumulation level of malondialdehyde decreased in pretreated plants. These findings indicate that NPR1 was activated through increasing in PAL, which in turn amplifies PR gene expression, effectively triggering SAR. In conclusion, salicylic acid application effectively strengthens rice plant resistance against infection by enhancing defense genes and antioxidant enzyme activity and offering a promising, eco-friendly strategy for managing bakanae disease.