Systemic Acquired Resistance (SAR)
Systemic Acquired Resistance (SAR) is a long-lasting and broad-spectrum defence mechanism that occurs when a pathogen infects turfgrass. Consequently, after infection, the pathogen triggers the salicylic acid pathway. Next, This induces defence response genes in the plant and then results in PR protein production.
Above all, salicylic acid plays a beneficial role in turfgrass management as it is a plant hormone that helps regulate various physiological processes in plants, including turfgrass.
Here are a few key roles of salicylic acid in turfgrass:
Disease resistance using salicylic acid for plants:
In short, this occurs as a result of salicylic acid boosting the plant’s immune system. It enhances the plant’s resistance to several diseases, in particular fungi or bacteria. It activates defence mechanisms within the plant, making it less susceptible to infections. For example, foliar applications of salicylic acid cause systemic acquired resistance (SAR) in plants, and provide protection against various biotic stresses.4
Salicylic acid enhances turfgrass resistance against turfgrass diseases such as dollar spot (caused by Sclerotinia homoeocarpa) and brown patch (caused by Rhizoctonia solani). It activates defence responses within the plant, including the production of antimicrobial compounds and reinforcement of cell walls, consequently, making it more difficult for fungi to infect the turfgrass.
In fact, It has been shown to be effective against grey leaf spot on turf type perennial ryegrass, giving a significant decrease in disease5.
Salicylic acid also helps turfgrass combat bacterial diseases like bacterial wilt (Ralstonia solanacearum) and bacterial leaf blight (Xanthomonas spp.). A series of growth chamber studies pre-treating plants with SA reduces disease symptoms of bacterial wilt in both creeping bentgrass ‘Penn-A4’ and ‘Tyee’.
SA application reduced disease in both cultivars under both optimal and high temperature treatments. Moreover, at both 23 °C and 35 °C, disease severity in plants with SA was less than in control plants.6
To sum up, it achieves this by stimulating the plant’s immune system to produce defence-related proteins, enzymes, and chemicals that can inhibit bacterial growth and limit disease progression.
While salicylic acid doesn’t directly target viruses, it can indirectly enhance turfgrass resistance to them. By activating systemic acquired resistance (SAR), salicylic acid helps the plant produce antiviral proteins that hinder the spread and replication of viruses.
Nematode resistance using salicylic acid for plants:
Salicylic acid increases turfgrass resistance against nematode infestations. Nematodes are microscopic worms that can damage turfgrass roots, leading to stunted growth and decline. Salicylic acid induces defence mechanisms in the plant, such as the release of nematode-repellent chemicals, which deter nematode feeding7 8
Research has even shown it repels certain insects such as thrips9, caterpillars10, and indirect effects on mite mortality11.12
Stress tolerance using salicylic acid for plants:
Turfgrass often faces environmental stressors, such as drought, heat, or cold. Salicylic acid helps the plant cope with these stresses by regulating various stress-responsive genes and biochemical pathways. It improves the resilience of turfgrass, therefore allowing it to withstand adverse conditions more effectively.
Salicylic acid influences the growth and development of turfgrass. It promotes root growth, leading to a healthier and more robust root system. Additionally, it can regulate shoot growth, helping to maintain a balanced growth pattern and overall turf quality.
Photosynthesis and chlorophyll production:
Finally, salicylic acid also enhances photosynthesis, which is crucial for the production of energy and the maintenance of turfgrass health. It can increase chlorophyll content, leading to greener and more vibrant turf.