4.1. Hyperparasites of plant-parasitic microfungi
Plant-parasitic microfungi are frequently colonized by hyperparasitic
fungi that are able to penetrate the hyphae, the spores, and/or the
reproductive structures of their fungal hosts (Gams et al., 2004;
Lumsden, 1992; Zhan et al., 2014). Some of these parasites are
specific to certain groups of plant pathogens and have garnered interest
as biocontrol agents, such as Ampelomyces quisqualis(Dothideomycetes: Pleosporales) (Fig. 7), a naturally occurring
hyperparasite of powdery mildews (Faticov et al., 2022; Huth et al., 2021). The most common plant-parasitic hosts include
species of powdery mildews (Erysiphaceae), black mildews (Meliolales),
tropical tarspot fungi (Phyllachorales), rusts (Pucciniales), and smuts
(Ustilaginales and further orders) (Gams et al., 2004;
Hawksworth, 1981). Information about hyperparasitic fungi on
plant-parasitic microfungi is scattered through literature, and there is
no detailed treatment of biotrophic plant pathogens and their
hyperparasites, as most publications deal with individual groups of
fungi (Bermúdez-Cova et al., 2022). Therefore, the following
sections offer a summary of hyperparasites attacking these major groups
of plant pathogens.