Ascomycotasienissä

The Ascomycota, often referred to as sac fungi, constitute one of the largest phyla of the kingdom Fungi. They are characterised by the production of sexual spores, known as ascospores, within specialised sac-like structures called asci (singular: ascus). These asci are typically formed inside fruiting bodies called ascocarps, which can be diverse in shape, ranging from simple cup-like structures to complex perithecia and inoperculate cleistothecia. Ascomycota fungi exhibit a wide range of growth forms, including unicellular yeasts, filamentous molds, and macroscopic fruiting bodies.

Reproduction in Ascomycota occurs through both sexual and asexual means. Asexual spores, called conidia, are produced on hyphae that branch from the main mycelium. In many species, asexual and sexual cycles are integrated: the same strain can switch between producing conidia and asci depending on environmental cues. Hyphal cells often display septa containing pores called dolipores, facilitating cytoplasmic streaming and material transport. Many species are heterothallic, requiring compatible mating types for sexual recombination, though some are homothallic or even self-fertile.

Ecologically, Ascomycota occupy pivotal roles as decomposers, pathogens, rhizosphere symbionts, and bioindicators. They decompose lignocellulosic material, recycles nutrients, and some form mycorrhizal associations with plants, enhancing nutrient uptake. Notably, several important plant pathogens belong to this phylum, such as *Puccinia* (rusts) and *Alternaria*. Conversely, numerous commercially valuable species produce antibiotics, enzymes, and food products. Brewer’s yeast (*Saccharomyces cerevisiae*) exemplifies the biotechnological importance of yeasts, contributing to bread, beer, and bioethanol production.

Taxonomically, Ascomycota are divided into several classes, including Leotiomycetes, Saccharomycetes, Eurotiomycetes, Dothideomycetes, and Sordariomycetes. DNA-based phylogenetics has refined relationships within the phylum, revealing that morphological traits alone are insufficient for resolving deep evolutionary lineages. Furthermore, environmental sequencing has highlighted a vast "dark matter" of uncultured ascomycetes, expanding our perception of their diversity and ecological significance.