Rapid Communication - International Research Journal of Plant Science ( 2025) Volume 16, Issue 3
Published: 20-Sep-2025
Biotic stress refers to damage caused to plants by living organisms, including pathogens, herbivores, nematodes, and parasitic weeds. These stressors significantly impact plant growth, yield, and survival, making biotic stress a major challenge in natural ecosystems and agricultural production. Plants have evolved sophisticated defense strategies involving structural barriers, biochemical defenses, and molecular signaling networks that detect and respond to invading organisms. Key components of the plant immune system include pattern recognition receptors that initiate PAMP-triggered immunity, and resistance (R) proteins involved in effector-triggered immunity. Hormonal pathways involving salicylic acid, jasmonic acid, and ethylene coordinate local and systemic defenses. Moreover, plants activate secondary metabolites and antimicrobial compounds to restrict pathogen growth. This article provides a comprehensive overview of plant responses to biotic stress, emphasizing defense mechanisms and their significance for crop improvement.
Biotic Stress, Plant Defense, Pathogens, Herbivores, Plant Immunity, Resistance Genes, Defense Signaling, Plant–Pathogen Interaction.
Biotic stress is a major factor limiting plant productivity and survival in both natural ecosystems and agricultural systems. It is caused by living organisms that derive nutrients from plants, often resulting in disease, tissue damage, or reduced reproductive success. Unlike abiotic stress, biotic stress involves dynamic interactions between plants and other organisms, making it highly complex and variable. Plants are constantly exposed to a wide range of pathogens, including bacteria, fungi, viruses, and oomycetes. These pathogens invade plant tissues, disrupt cellular processes, and interfere with nutrient transport (Morkunas et al., 2018). Disease outbreaks can lead to severe yield losses and threaten food security, particularly in monoculture-based agricultural systems. Herbivorous insects represent another significant source of biotic stress. Feeding damage caused by chewing or sap-sucking insects reduces photosynthetic capacity and weakens plant structure. Insects may also act as vectors for plant viruses, increasing the severity of stress. Plants have evolved both direct and indirect defenses to minimize insect damage (Amirsadeghi et al., 2007). The first line of plant defense against biotic stress is the presence of physical and structural barriers. The cuticle, cell wall, and waxy surfaces restrict pathogen entry and insect feeding. Trichomes, spines, and thickened tissues further deter herbivores and reduce susceptibility to attack. When pathogens overcome physical barriers, plants activate innate immune responses. Pattern recognition receptors located on the cell surface detect conserved microbial molecules and initiate defense signaling. This process, known as PAMP-triggered immunity, restricts pathogen growth by activating antimicrobial responses and reinforcing cell walls (Suzuki et al., 2014). Some pathogens secrete effector molecules that suppress plant immunity and promote infection. In response, plants have evolved resistance genes that recognize these effectors and activate effector-triggered immunity. This response is often rapid and intense, involving localized cell death to prevent pathogen spread. Plant hormones play a crucial role in coordinating biotic stress responses. Salicylic acid is primarily associated with resistance to biotrophic pathogens, while jasmonic acid and ethylene regulate defenses against necrotrophs and herbivorous insects (Peterson & Higley, 2000). The balance and interaction among these hormones determine the effectiveness of defense responses. Plants also produce a diverse range of secondary metabolites that act as chemical defenses. Compounds such as alkaloids, phenolics, terpenoids, and phytoalexins inhibit pathogen growth or reduce herbivore feeding. These compounds may be constitutively present or synthesized rapidly in response to attack. Beneficial microorganisms can enhance plant resistance to biotic stress. Certain rhizobacteria and mycorrhizal fungi induce systemic resistance, priming plants to respond more effectively to future attacks. These beneficial interactions offer sustainable alternatives to chemical pesticides. Understanding biotic stress mechanisms is essential for crop improvement and sustainable agriculture. Advances in molecular genetics and biotechnology have enabled the identification of resistance genes and defense pathways that can be exploited in breeding programs. Developing crops with durable resistance is critical for minimizing yield losses and reducing environmental impacts (Lal et al., 2018).
Biotic stress remains a persistent threat to plant health, driven by complex interactions with pathogens and herbivores. Plants counter these challenges through integrated defense systems involving physical barriers, immune signaling, hormonal regulation, and chemical defenses. Beneficial microbial associations further strengthen plant resistance and resilience. Continued research into biotic stress responses is essential for developing resistant crop varieties and sustainable agricultural practices. Strengthening plant defense mechanisms will play a vital role in ensuring global food security and ecosystem stability under increasing biological pressures.
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