María Fernanda Paletti Rovey

Wheat (Triticum aestivum L.) is one of the most important cereals worldwide, but is affected by various bacterial diseases, including bacterial leaf blight caused by Pseudomonas syringae, that decrease productivity significantly. The indiscriminate use of synthetic pesticides for disease management has led to environmental contamination, development of resistance and health risks, highlighting the need for alternative and environmentally friendly solutions. In this study, phytopathogenic Pseudomonas were isolated from symptomatic wheat leaves collected in Córdoba province (Argentina). The isolates were phenotypically identified using biochemical tests and the LOPAT scheme, confirming their classification within Group I of P. syringae. Pathogenicity tests verified their ability to induce typical leaf blight symptoms, and nine isolates were positive for the production of syringomycin, a phytotoxin associated with host tissue necrosis. The antimicrobial activity of different phytochemical preparations obtained from Thymus vulgaris and Origanum vulgare (decoctions, alcoholic, hexanic, chloroformic and propanolic extracts, as well as essential oils (EOs)) against the isolated and reference strains of P. syringae was evaluated. Disk diffusion assays revealed that thyme and oregano EOs exhibited the strongest inhibitory effects compared to the other phytochemical preparations tested. Antimicrobial activity assays by broth microdilution technique confirmed the antibacterial potency of thyme EO (MIC = 1.43–22.99 mg/mL) and oregano EO (MIC = 2.89–23.13 mg/mL). These results demonstrated the efficacy of T. vulgaris and O. vulgare EOs as natural antimicrobial agents, suggesting their potential application as sustainable alternatives to synthetic pesticides for the control of bacterial leaf blight in wheat crops.

Dada su inmensa extensión geográfica, Argentina resguarda una sorprendente variedad de especies vegetales, y la provincia de Córdoba se destaca como una de las principales proveedoras de especies aromáticas y medicinales autóctonas al mercado nacional. Estas plantas, en su mayoría, provienen de los Departamentos del Oeste de la provincia, una región que alberga una gran diversidad de estas especies. En los últimos años, los colegios de nivel medio de esta región han estado trabajando arduamente en el aprendizaje y la preservación de la flora local. Estos esfuerzos incluyen el estudio de las diferentes variedades de plantas, sus métodos de cultivo, propiedades y usos populares. Simultáneamente, docentes e investigadores de la Universidad Nacional de Río Cuarto han llevado a cabo investigaciones exhaustivas sobre plantas medicinales, evaluando diversas propiedades biológicas, como su capacidad antimicrobiana, citotóxica, antiinflamatoria, entre otras. Como parte de un proyecto de divulgación científica, se llevaron a cabo una serie de actividades en colegios de nivel medio de la región de Córdoba con el propósito de transmitir las vastas experiencias acumuladas a lo largo de años de investigación por parte de docentes e investigadores a estudiantes y a la comunidad en general. Estas actividades comprendieron tanto aspectos teóricos como prácticos, y culminaron en la creación de un documento de divulgación científica titulado "Una Farmacia en el Monte". En este libro se profundiza en la relevancia de las plantas autóctonas y su potencial farmacológico, además de promover la conservación de estas especies para que los estudiantes de la región se conviertan en agentes multiplicadores de este conocimiento. Tanto los estudiantes de nivel medio como la sociedad en general se beneficiaron al ser receptores de los estudios científicos realizados hasta el momento, lo que aumentó la conciencia sobre la importancia de la vegetación autóctona en los ecosistemas y su preservación, con el fin de mantener el equilibrio ecológico y aprovechar al máximo sus propiedades medicinales.

Phytopathogenic bacteria not only affect crop yield and quality but also the environment. Understanding the mechanisms involved in their survival is essential to develop new strategies to control plant disease. One such mechanism is the formation of biofilms; i.e., microbial communities within a three-dimensional structure that offers adaptive advantages, such as protection against unfavorable environmental conditions. Biofilm-producing phytopathogenic bacteria are difficult to manage. They colonize the intercellular spaces and the vascular system of the host plants and cause a wide range of symptoms such as necrosis, wilting, leaf spots, blight, soft rot, and hyperplasia. This review summarizes up-to-date information about saline and drought stress in plants (abiotic stress) and then goes on to focus on the biotic stress produced by biofilm-forming phytopathogenic bacteria, which are responsible for serious disease in many crops. Their characteristics, pathogenesis, virulence factors, systems of cellular communication, and the molecules implicated in the regulation of these processes are all covered.

As a follow-up to previous studies, the effects of Thymus vulgaris essential oil on selected virulence factors (growth, sessile cell survival, swimming, swarming, and exopolysaccharide production) were evaluated in phytopathogenic Pseudomonas syringae strains isolated from soybean fields in Argentina; reference strains Pseudomonas savastanoi pv. glycinea B076 and Pseudomonas aeruginosa PAO1. P. syringae are responsible for bacterial blight, a disease that affects crops worldwide. Plant bacterioses are usually treated with antibiotics and copper compounds, which may contribute to the development of resistance in pathogens and damage the environment. For these reasons, eco-friendly alternatives are necessary. Although aromatic plants are a natural source of antimicrobial substances, the effects of these substances on phytopathogenic bacteria remain largely unexplored. Subinhibitory concentrations of the oil significantly reduced the slope and rate of bacterial growth. In addition, biofilm and exopolysaccharide (EPS) production were inhibited, with swimming and swarming motility patterns being affected at all of the oil concentrations tested. Therefore, TEO could potentially be a highly efficient antipseudomonal agent for treating plant infections caused by P. syringae.

Introduction: Paenibacillus larvae is a spore-forming bacillus, the most important bacterial pathogen of honeybee larvae and the causative agent of American foulbrood (AFB). Control measures are limited and represent a challenge for both beekeepers and researchers. For this reason, many studies focus on the search for alternative treatments based on natural products. Aim: The objective of this study was to determine the antimicrobial activity of the hexanic extract (HE) of Achyrocline satureioides on P. larvae and the inhibitory activity on some mechanisms related to pathogenicity. Material and methods: The Minimum Inhibitory Concentration (MIC) of the HE was determined by the broth microdilution technique and the Minimum Bactericidal Concentration (MBC) by the microdrop technique. Swimming and swarming motility was evaluated in plates with 0.3 and 0.5% agar, respectively. Biofilm formation was evaluated and quantified by the Congo red and crystal violet method. The protease activity was evaluated by the qualitative technique on skim milk agar plates. Results: It was determined that the MIC of the HE on four strains of P. larvae ranged between 0.3 and 9.37 µg/ml and the MBC between 1.17 and 150 µg/ml. On the other hand, sub-inhibitory concentrations of the HE were able to decrease swimming motility, biofilm formation and the proteases production of P. larvae.