Biocontrol of tomato Verticillium wilt disease by plant growth-promoting bacteria encapsulated in alginate extracted from brown seaweed.

The use of beneficial microorganisms and polysaccharides for the biocontrol of plant diseases currently represents a promising tool for the management of soil-borne pathogens. Despite advancements, enhancing the efficacy and sustainability of these biocontrol methods, particularly in complex soil environments, remains a challenge. Thus, we investigated the potential of four PGPR strains encapsulated in natural alginate extracted from a brown seaweed Bifurcaria bifurcata to evaluate its biocontrol capacities against Verticillium wilt of tomato, ensuring optimal performance through a synergistic effect and innovative bacterial release. Our research demonstrated that the application of PGPR and alginate reduced disease severity and mortality rate and increased the natural defenses of tomato. Results showed that supplying alginate or the PGPR consortium at the root level s stimulates phenylalanine ammonia-lyase activity (the key enzyme of the phenylpropanoid metabolism) and the accumulation of phenolic compounds and lignin in leaves and roots. Treatment with PGPR encapsulated in alginate beads showed the best biocontrol efficiency and was accompanied by a synergistic effect reflecting a rapid, intense, and systemic induction of defense mechanisms known for their effectiveness in inducing resistance in tomato. These promising results suggest that such bioformulations could lead to innovative agricultural practices for sustainable plant protection against pathogens.

Preparation of bioactive film based on chitosan and essential oils mixture for enhanced preservation of food products.

Recently, the concept of biodegradable and bioactive packaging and surface coating has become a trend. In this work, the bioactive films of chitosan were elaborated following the casting method. Contrary to the films containing the Cinnamomum zeylanicum Blume, Thymus satureioides Cosson, and Syzygium aromaticum essential oils (EOs) mixtures, the control film was thin, colorless, and showed high moisture content, swelling degree, and elongation at break. Concerning the physicochemical parameters, the incorporation of the EOs mixtures minimized the hydrophobicity of the material (θw < 65°) and modified randomly its surface free energy components (γ-; γ+; γLW). The theoretical prediction of Aspergillus sp. and Rhizopus sp. adherence to the chitosan-based films was relatively correlated to the experimental results (r = -0.601). The latter showed that 6.80 % and 19.02 % of the control film surface was covered by Aspergillus sp. and Rhizopus sp. spores, respectively. In contrast, no fungal adherence was noticed in the case of the film incorporating the triple EOs mixture. These promising results revealed that chitosan film containing C. zeylanicum, T. satureioides, and S. aromaticum EOs mixtures could be utilized as a surface coating or bioactive packaging in the food industry.