Yeasts in agricultural and managed soils

Abstract

All managed soils (agricultural soil, orchard soil, vineyard soil, pasture soil) are exposed to human intervention. These include regular tillage, crop or plant seeding, harvesting and the application of fertilizers, herbicides and pesticides. Yeasts are present in all types of managed soil; some of them are restricted to an individual season, soil horizon or locality, while others are present at all times in all soils. The abundance of yeasts depends on the availability of water, the type of soil and plant diversity. The composition and quantity of soil yeast communities are influenced by the yeasts originating from aerial parts of plants, which enter the soil during tillage or with decaying plant material. The size of the yeast population ranges from a few to several thousands of CFU per gram of soil. The diversity of ascomycetous yeasts present in agricultural soil includes fermentative species (e.g. Candida spp., Metschnikowia sp.), soil-related yeasts (e.g. Cyberlindnera saturnus and Lipomyces sp.), black yeasts (Exophiala sp., Aureobasidium sp.) and basidiomycetous yeasts, mainly species previously classified in the genera Cryptococcus and Trichosporon. Vineyard soils are inhabited by basidiomycetous yeasts (mainly Naganishia spp., Sollicoccozyma spp., Filobasidium sp.) and also by grape yeasts including Aureobasidium pullulans, Metschnikowia sp. and Hanseniaspora uvarum. In orchard soils, fruit-related yeasts H’spora uvarum and Metschnikowia pulcherrima are associated with the upper layer of soil. Species previously classified in the genera Cryptococcus and Trichosporon dominate the soil of citrus orchards. Grassland soils are mainly occupied by soil-related ascomycetous species Schwanniomyces capriotti, Barnettozyma vustinii and Cyberlindnera suaveolens.