Food losses, defined as a reduction in the quantity and quality of food during production and storage, impact food safety and security. Losses caused by plant pathogens are among the most significant. Chemical pesticides have been extensively used to prevent microbial diseases. Their toxicity and reduced efficacy, however, have encouraged investigators to develop alternatives. Alternatives based on microbial biopesticides tend to be safer and more environmentally benign than conventional pesticides. In recent years, formulations based on biopesticides have progressively increased in number and diversity and have attracted commercial interest. Understanding the mechanisms by which biopesticides control the disease is fundamental to achieving optimal disease control. Biocontrol mechanisms can be divided into two main categories: those related to the ability to inhibit pathogens or their virulence factors, and those that enhance host plant fitness and induce disease resistance. Here, the first type of strategy is reviewed, which is directly mediated by physical contact between biocontrol agents and pathogens or indirectly by exposure of a pathogen to antimicrobial or microbial-inhibiting compounds produced by the microbial antagonist. Mechanisms involving physical contact include mycophagy, destruction of pathogenic bacteria by bacteriophages or predation, and disease inhibition by topical applications of specific dsRNA. Indirect mechanisms that do not involve direct contact with a pathogen include the production of antimicrobial compounds, competition, and virulence factor suppression by quorum quenching. These topics are reviewed and discussed.

The capacity of microorganisms from water kefir (WK) to control Aspergillus flavus growth during the aerobic phase of ensiled sorghum grains was determined. Sorghum inoculated with A. flavus was treated with filter-sterilized and non-sterilized water kefir, ensiled, and incubated 7 days at 25 °C. A. flavus growth was quantified by qPCR after incubation. Mold growth was inhibited in the presence of water kefir while no inhibition was observed when filter-sterilized water kefir was applied, demonstrating the relevant role of the microorganisms in the kefir water in the biocontrol process. Fungal and bacterial diversity in treated sorghum mini-silos was analyzed by high-throughput sequencing. Firmicutes was the predominant bacterial phyla and Lactobacillus represented the most abundant genus, while Ascomycota was the predominant fungal phyla with Saccharomyces and Pichia as the major genera. Bacterial and yeast counts before and after incubation indicated that the microbial community obtained from WK was able to grow in the sorghum mini-silos in the presence of A. flavus. Results of the present work indicate that the use of a mixed inoculum of microorganisms present in WK may represent an alternative management practice to avoid the growth of A. flavus in ensiled sorghum grains and the concomitant contamination with aflatoxins.

La fusariosis de la espiga (FE) es una enfermedad que causa grandes pérdidas de rendimiento y calidad en granos de trigo a nivel mundial. Es producida principalmente por hongos del complejo Fusarium graminearum, los cuales en su mayoría producen micotoxinas que contaminan los granos afectados. El inóculo primario de la enfermedad proviene de los rastrojos del cultivo del año anterior. En condiciones ambientales adecuadas ascosporas o conidias del patógeno infectan las flores que constituyen el órgano susceptible de la planta. Las medidas de control incluyen prácticas culturales y aplicación de fungicidas. Sin embargo, ninguna práctica es por sí sola totalmente efectiva. En este contexto el uso de control biológico surge como una medida complementaria. El objetivo de este trabajo consistió en aislar y seleccionar cepas nativas de Trichoderma spp. para el control del inóculo primario de FE en trigo. Se trabajó con 16 cepas de Trichoderma identif icadas a nivel de especie las cuales exhibieron una o varias actividades que podrían relacionarse con su potencial como agente de biocontrol. Una de las cepas identif icada como T. atroviride, fue seleccionada con base en su habilidad para inhibir la formación de peritecios por parte del patógeno sobre rastrojo de trigo y su capacidad de producción de enzimas asociadas a la degradación del rastrojo que sirve de soporte al patógeno.