Scientific Publications
In search of Metschnikowia yeasts for use as biocontrol agents
Antonie van Leeuwenhoek
Different yeast species have been used as effective biological control agents (BCA) against a variety of plant pathogens. Biocontrol yeasts inhibit the growth of targeted pathogens by various ways and mechanisms. Competition for nutrients and space, secretion of specific lytic enzymes, secretion of inhibitory metabolites as well as stress tolerance are the main modes of their action. To search for new BCAs, researchers often focus on epiphytic yeasts isolated from natural environments. Such yeasts are especially useful as their occurrence in a specific habitat is often as a result of successful competition against other microorganisms. In this study, we have isolated Metschnikowia spp. strains from flowers and fruits collected in Poland. The plant material was collected between April to September 2017 from two small orchards where traditional organic management is employed. Yeast screening was carried out using YPD agar supplemented with chloramphenicol and Fe(III) ions. Taxonomic classification was determined by sequence analysis of the D1/D2 domains of the large subunit (LSU) rRNA gene, and the isolates were identified as Metschnikowia andauensis and M. sinensis. Yeast isolates were further characterized based on their enzymatic and assimilation profiles as well as their growth under various stress conditions. In addition, the hydrophobicity and adhesive abilities of the Metschnikowia isolates were determined using a MATH test and luminometry. The antagonistic action against molds representing typical crop spoiling microflora was also evaluated. The assimilation profiles of the wild isolates were similar to those displayed by collection strains of M. pulcherrima. However, some isolates displayed more beneficial phenotypic properties, especially good growth under stress conditions. Some epiphytes grew well over a wider range of temperatures (8 – 30 °C), pH level (3 – 9), showed elevated tolerance to ethanol (8%), glucose (30%) and peroxides (50 mM). Hydrophobicity and adhesion of yeast cells were strain- and surface-dependent. Tested yeasts showed interesting features as potential BCAs, with some isolates exhibiting strong antagonism against molds belonging to the genera Alternaria, Botrytis, Fusarium, Rhizopus, Verticillium, as well as against yeasts isolated as food spoilage microbiota.
Antonie van Leeuwenhoek
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