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<p>The aim of this study is to investigate whether the activation of plant defense systems and the type of defense compounds depends on the population or threat of microorganisms when plants are simultaneously challenged by different pathogens or by non-pathogenic organisms or a combination of both in different population ratios. This study focuses on root-knot nematodes and Fusarium vascular wilt, along with the non-pathogenic bacterium <i>Bacillus subtilis</i>, applied in various combinations to tomato plants. The results show that in addition to reducing the pathogenicity indices of nematodes and fungi by <i>Bacillus subtilis</i> as a biocontrol agent and also the disease synergy between the two pathogens, plant defense responses are also induced with different quantity and quality. Chitinase enzyme activity is significantly increased in response to the fungal pathogen compared to the nematode, while protease activity is significantly higher against the RK-nematode. When the plant is simultaneously attacked by two pathogens or by a pathogen and a non-pathogen, the activation of defense responses appear to be dictated by the intensity of signaling from the organism with the larger population. Notably, RK-nematodes demonstrate a pronounced ability to suppress the plant’s defense mechanisms. However, certain compounds, such as hydrogen peroxide, as well as specific defense enzymes like phenylalanine ammonia lyase, exhibit varying degrees of response to these suppressive effects. This study underscores the complexity of plant-pathogen interactions and highlights the significance of pathogen population dynamics in shaping plant defense strategies.</p>

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Resistance induced in tomato plants with pathogenic and non-pathogenic agents: plasticity and differentiation

  • 期刊论文

  • 发表日期：

    2026年7月21日

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  • Shiva Behzadian,
  • Navazollah Sahebani

摘要

The aim of this study is to investigate whether the activation of plant defense systems and the type of defense compounds depends on the population or threat of microorganisms when plants are simultaneously challenged by different pathogens or by non-pathogenic organisms or a combination of both in different population ratios. This study focuses on root-knot nematodes and Fusarium vascular wilt, along with the non-pathogenic bacterium Bacillus subtilis, applied in various combinations to tomato plants. The results show that in addition to reducing the pathogenicity indices of nematodes and fungi by Bacillus subtilis as a biocontrol agent and also the disease synergy between the two pathogens, plant defense responses are also induced with different quantity and quality. Chitinase enzyme activity is significantly increased in response to the fungal pathogen compared to the nematode, while protease activity is significantly higher against the RK-nematode. When the plant is simultaneously attacked by two pathogens or by a pathogen and a non-pathogen, the activation of defense responses appear to be dictated by the intensity of signaling from the organism with the larger population. Notably, RK-nematodes demonstrate a pronounced ability to suppress the plant’s defense mechanisms. However, certain compounds, such as hydrogen peroxide, as well as specific defense enzymes like phenylalanine ammonia lyase, exhibit varying degrees of response to these suppressive effects. This study underscores the complexity of plant-pathogen interactions and highlights the significance of pathogen population dynamics in shaping plant defense strategies.