Genotype-Dependent Interactions Between Biostimulants and Defense Inducers in Durum Wheat: Implications for Sustainable Crop Management

The intensive use of synthetic pesticides and fertilizers has raised environmental concerns. Sustainable alternatives, such as plant biostimulants and plant resistance inducers, offer promising solutions by enhancing growth, yield, and stress tolerance or by activating defense responses against pathogens. However, the physiological impacts and combined effects of these products remain poorly understood, limiting evidence-based application strategies. Here, we evaluated the effects of a biostimulant and a plant defense inducer on durum wheat (Triticum turgidum ssp. durum), a key cereal crop in the Mediterranean Basin. Using controlled experiments, we assessed plant growth, chlorophyll content, defense gene expression and resistance to Zymoseptoria tritici, while considering potential trade-offs between growth promotion and defense activation. As expected, our results indicate that the biostimulant improved photosynthetic performance (19 to 45%), whereas the plant resistance inducer enhanced protection against Z. tritici (25% reduction in pycnidia). However, the combination of these two treatments can induce moderated interaction effects influenced by the varietal genetic background. This study provides novel insights into the interactions between plant growth promotion and defense induction in durum wheat. Understanding these multifactorial effects (in particular genotype effect) enables the identification of optimal treatment strategies, supporting the development of sustainable crop management practices that reduce chemical inputs while maintaining productivity and resilience under biotic stress.