Abstract

The increasing concerns over the environmental and human health impacts of pesticide use have driven the search for sustainable alternatives in plant protection. One of the most promising approaches is the use of plant resistance inducers, which activate the plant’s natural defense mechanisms rather than directly targeting pathogens. These inducers stimulate systemic acquired resistance (SAR) providing broad-spectrum and long-lasting protection against various biotic stress factors. Our research focuses on the development of novel plant resistance inducers based on salicylic acid derivatives, which could serve as environmentally friendly alternatives to conventional pesticides in multiple crop species.

Salicylic acid (SA) is a well-known phytohormone involved in plant immunity, playing a crucial role in the activation of SAR. However, its direct application is often limited by low solubility, instability, and potential phytotoxicity at high concentrations. To overcome these limitations, we designed new SA derivatives in the form of ionic compounds, where the counterion is a naturally occurring, biodegradable ion with low toxicity. These newly synthesized compounds were evaluated for their ability to enhance plant defense responses against fungal and bacterial pathogens in multiple crop species, including wheat (Triticum aestivum), potato (Solanum tuberosum), and apple (Malus domestica).

Our field and laboratory trials demonstrated that salicylates effectively reduced the incidence of economically important diseases such as powdery mildew (Blumeria graminis), septoria leaf blotch (Zymoseptoria tritici), and late blight (Phytophthora infestans) in wheat and potato crops. In apples, these compounds significantly suppressed infections caused by Venturia inaequalis (apple scab) and Erwinia amylovora (fire blight), achieving disease control levels comparable to conventional fungicides.

An important advantage of these novel resistance inducers is their compatibility with integrated pest management (IPM) strategies. Unlike traditional fungicides and bactericides, which exert selective pressure on pathogens and contribute to the development of resistance, SAR inducers promote plant resilience without directly affecting microbial populations. This makes them suitable for long-term use in sustainable agriculture. Additionally, their application has been associated with increased chlorophyll content, improved photosynthetic efficiency, and enhanced nutrient uptake, leading to measurable yield improvements. For instance, in wheat trials, yield increases of 10.6–11.6% were recorded, while in potato, tuber production rose by 21.6% following treatment with salicylate-based inducers.

The European Union’s policies on pesticide reduction, including the Green Deal and the Farm to Fork strategy, further emphasize the need for alternatives that maintain agricultural productivity while minimizing environmental harm. Our findings suggest that tailored salicylates have the potential to become a key component of next-generation plant protection, helping to reduce pesticide dependency while ensuring effective disease control. The ability of these compounds to induce plant resistance across different crop species underscores their broad applicability and commercial potential.

In conclusion, plant resistance inducers based on modified salicylic acid derivatives present a promising alternative to conventional pesticides, offering effective, sustainable, and environmentally safe crop protection. By harnessing the plant’s own defense mechanisms, these compounds contribute to more resilient agricultural systems and align with global efforts to reduce the ecological footprint of modern farming. Future research will focus on optimizing formulations, understanding the molecular mechanisms of action, and scaling up field applications to facilitate their adoption in commercial agriculture.

The “Searching for new chemical compounds inducing resistance of apple to diseases and determination of the molecular mechanism of their action” project is carried out within the Sonata (UMO47/2022-/D/NZ02327/9) programme of the National Science Center, Poland