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<p>Okra (<i>Abelmoschus esculentus</i> (Linn.) Moench), a globally cultivated vegetable crop valued for its nutrient-rich pods, is facing emerging threats from seedling damping-off and blight in subtropical regions of South China. In 2022, fungal isolates representing five genera (<i>Trichoderma</i>, <i>Rhizoctonia</i>, <i>Rhizopus</i>, <i>Macrophomina</i>, and <i>Rhizomucor</i>) were obtained from symptomatic seedlings in Guangdong Province. The pathogenicity test revealed that three <i>Rhizoctonia</i> isolates (ACCC 35247, ACCC 35460 and ACCC 35461) could induce typical damping-off symptoms, inhibit seed germination and cause hypocotyl necrosis, consistent with symptoms observed under natural field conditions. Based on morphological and molecular characterization, along with phylogenetic analysis of the ITS region, the pathogen was identified as <i>Rhizoctonia solani</i> (teleomorph: <i>Thanatephorus cucumeris</i> (Frank) Donk). The mycelial and sclerotia lethal temperature of the pathogen was 45&#xa0;°C and 48&#xa0;°C respectively, and the optimal temperature (T<sub>opt</sub>) for mycelial growth was 28.22&#xa0;°C. Sensitivity of the pathogen to seven fungicides was evaluated in vitro using a mycelial radial growth assay, the EC<sub>50</sub> values for each fungicide were estimated. According to the EC<sub>50</sub> values of seven fungicides, there was significant difference in the inhibitory effect of each fungicide on the pathogen, and the pathogen was most sensitive to trifloxystrobin + tebuconazole (1:2),&#xa0;with the mean EC<sub>50</sub> value being 0.43 mg·L<sup>−1</sup>. This study provides critical insights into the disease management of <i>R. solani</i> induced damping-off in okra.</p>

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Rhizoctonia solani causes okra (Abelmoschus esculentus) seedling damping-off in South China with biological characterization and fungicide sensitivity profiling

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年10月1日

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  • Run Hua Yi,
  • Xiao Min Zeng,
  • Ke Yu Li,
  • Yan Huang,
  • Xiao Chun Chen

摘要

Okra (Abelmoschus esculentus (Linn.) Moench), a globally cultivated vegetable crop valued for its nutrient-rich pods, is facing emerging threats from seedling damping-off and blight in subtropical regions of South China. In 2022, fungal isolates representing five genera (Trichoderma, Rhizoctonia, Rhizopus, Macrophomina, and Rhizomucor) were obtained from symptomatic seedlings in Guangdong Province. The pathogenicity test revealed that three Rhizoctonia isolates (ACCC 35247, ACCC 35460 and ACCC 35461) could induce typical damping-off symptoms, inhibit seed germination and cause hypocotyl necrosis, consistent with symptoms observed under natural field conditions. Based on morphological and molecular characterization, along with phylogenetic analysis of the ITS region, the pathogen was identified as Rhizoctonia solani (teleomorph: Thanatephorus cucumeris (Frank) Donk). The mycelial and sclerotia lethal temperature of the pathogen was 45 °C and 48 °C respectively, and the optimal temperature (Topt) for mycelial growth was 28.22 °C. Sensitivity of the pathogen to seven fungicides was evaluated in vitro using a mycelial radial growth assay, the EC50 values for each fungicide were estimated. According to the EC50 values of seven fungicides, there was significant difference in the inhibitory effect of each fungicide on the pathogen, and the pathogen was most sensitive to trifloxystrobin + tebuconazole (1:2), with the mean EC50 value being 0.43 mg·L−1. This study provides critical insights into the disease management of R. solani induced damping-off in okra.