SAR: Systemic Acquired Resistance

Systemic Acquired Resistance (SAR) is a crucial defense mechanism in plants that provides resistance against a wide range of pathogens, including bacteria, viruses, fungi, and other pests. SAR is a type of induced systemic resistance, which means that it’s activated throughout the entire plant following an initial localized exposure to a pathogen or its elicitors (substances that trigger a response).

Here’s how SAR works and its key features:

1. Initiation and Priming: SAR is initiated when a plant is exposed to a pathogen or pathogen-derived molecules, known as pathogen-associated molecular patterns (PAMPs). The plant’s immune system detects these invaders and undergoes priming, preparing the plant to respond more effectively to subsequent pathogen attacks.
2. Signal Transmission and Defense Activation: The detection of the pathogen triggers a signaling cascade within the plant. Signals, such as salicylic acid (SA), are produced and transported to other parts of the plant, inducing a systemic response. These signals activate the plant’s defense mechanisms, making it more resistant to future infections.
3. Systemic Spread of Resistance: The defense response induced by SAR is systemic, meaning it spreads throughout the plant from the initial infection site. This allows the entire plant to be prepared to resist potential attacks, even in areas distant from the primary infection site.
4. Accumulation of Pathogenesis-Related (PR) Proteins: SAR leads to the accumulation of pathogenesis-related (PR) proteins, which are involved in defense against a broad range of pathogens. These PR proteins have antimicrobial properties and play a key role in the plant’s defense against infections.
5. Long-lasting and Memory-based Response: SAR provides a long-lasting resistance and creates a sort of immunological memory within the plant. The plant “remembers” the pathogen and responds more robustly and swiftly upon subsequent encounters with the same or related pathogens.
6. Cross-Resistance: SAR can confer resistance not only to the original pathogen but also to unrelated pathogens. This phenomenon, known as cross-resistance, broadens the plant’s defense capabilities.
7. Role of SA in SAR: Salicylic acid (SA) is a critical signaling molecule in the development of SAR. It orchestrates the expression of defense-related genes and activates the production of PR proteins, resulting in enhanced resistance against pathogens.

SAR is a crucial aspect of plant immunity and an important tool in integrated pest management and sustainable agriculture. Understanding SAR and its mechanisms can aid in the development of strategies to enhance plant resistance to diseases, reducing the dependence on chemical pesticides.

Talk to your OMEX representative today to learn more about how to elicit Systemic Acquire Resistance in your crop and promote health and tolerance to diseases and pest.