BIOPROTECTIVE POTENTIAL OF RHAMNOLIPID NANOEMULSIONS CONTAINING ESSENTIAL OILS AGAINST PATHOGENIC MICROORGANISMS AFFECTING CROPS OF AGRO-INDUSTRIAL INTEREST

KOURDOVA, LUCILLE TIHOMIROVA; HARO, NICOLÁS; MOTTOLA, MILAGRO; FANANI, MARÍA LAURA; MENEGUZZI, NATALIA; FABRO, GEORGINA

Córdoba

Congreso; LX Congreso SAIB 2024; 2024

Sociedad Argentina de Bioquímica y Biología Molecular

Common bean (Phaseolus vulgaris) is the third most consumed legume worldwide, and Argentina is its main exporter. Yield losses of this crop are due to climatic factors and diseases caused by fungi, viruses, and bacteria. Bacterial bean blight, caused by species of the genus Xanthomonas and Pseudomonas, manifests as yellow-green halo lesions on leaves, pods, stems, or petioles. This disease leads to significant crop losses globally and is challenging to control, as no curative, only preventive treatments are available. To combat plant diseases, one effective strategy is to enhance plants´ innate defense mechanisms, a process known as priming, which induces a broad-spectrum immunological memory state. Rhamnolipids (RLs), compounds produced by various microorganisms, are known for their direct antibacterial and antifungal properties. They also stimulate the innate immune system of plants and are considered promising for agricultural use due to their biodegradability and low ecotoxicity. Additionally, RLs function as excellent emulsion stabilizers, enabling the formation of vesicles that can encapsulate hydrophobic antimicrobial molecules, such as essential oils (EOs). This encapsulation enhances the efficacy of these compounds by optimizing their stability and delivery, thereby improving their overall protective effects on plants. We developed nanoemulsions (NEs) of RLs containing EOs from rue, thyme, and tea tree. Their application by spraying over leaves of the model plant Arabidopsis thaliana improved its immune response against the phytopathogenic bacteria Pseudomonas syringae pv tomato DC3000. In addition, the NEs did not show a detrimental effect on the native soil microbiota and beneficial microorganisms that are commonly used as seed bioinoculants. Thus, to test the effect of NEs over pathogens of crops of agro-industrial significance, we evaluated their impact on the growth “in planta” of. Xanthomonas spp., isolated from common bean seeds (fields) by Dr. Natalia Meneguzzi. None of the foliar pre-treatments performed with NEs/RLs caused visible damage to the leaves, nor visibly reduced the symptoms of infection, suggesting that these treatments, at the applied doses, were not effective in combating this bacterial disease, at least in leaves. However, RLs demonstrated a direct inhibitory effect on the growth of Xanthomonas in vitro. The use of certified, disinfected, and pathogen-free seeds is one of the most widely used preventive strategies. Considering that RLs exerted a direct effect on the growth of Xanthomonas in vitro, we continue exploring the potential of NEs as a seed treatment and will present our most recent results.