ABSTRACT
Crop diseases caused by fungi or oomycetes are responsible for significant losses in food production worldwide, and are increasingly recognized as a global threat to food security. This crisis derives from concurring factors, which include agricultural practices, global trade and climate change, all of which synergistically impact plants’ fitness, critical to the maintenance of function and services of agro-ecosystems. Yeasts are part of the plant holobiont, in the phytosphere, rhizosphere and adjacent soil, where they play mostly unknown roles, which do not include damage or disease to plants. In other respects, yeasts have beneficial potential for the biological control of fungal diseases and as promoters of plant health and growth. Their roles as endophytes, mutualists and as part of roots and soils microbiome are presented and discussed in this chapter , as are the ways by which yeasts kill fungi. These include the secretion of Killer toxins, hydrolytic enzymes, small peptides, siderophores and/or VOCs. Some species also act as necrotrophic mycoparasites. Yeasts’ resilience in face of environmental stress, specificity of action and amenability towards plants and humans, together with their fast proliferation, make them significant candidates for utilization in sustainable agriculture practices, both as BCAs and PGPs, urging research in this regard.
