ascomycetes

Ascomycetes, also known as sac fungi, form one of the largest phyla of fungi and include a wide range of forms from single-celled yeasts to large cup- or truffle-like structures. They are characterized by the production of sexual spores inside sac-like cells called asci, which are typically housed within a fruiting body called an ascocarp. Most asci contain eight ascospores, produced after meiosis and a brief mitotic division following karyogamy. Many ascomycetes also reproduce asexually by producing conidia, enabling rapid dispersal.

Sexual reproduction in ascomycetes involves hyphal fusion (plasmogamy) followed by the formation of asci within various types of ascocarps. Ascocarps come in several forms, including apothecia (open cup-shaped), perithecia (closed, flask-shaped), and pseudothecia (embedded sacs). Some species have a dominant asexual stage and are known only from their anamorphs. Hyphae are typically septate and may form a wide range of structures, from yeast-like cells to elaborate fruiting bodies.

Ecology and importance: ascomycetes are ubiquitous in soils, on plant surfaces, and in decaying material. They are major decomposers and include many plant pathogens, endophytes, and mutualists. They also play a prominent role in biotechnology and food production; Saccharomyces cerevisiae is central to baking and brewing, while Aspergillus and Penicillium species contribute to food production and enzyme synthesis. Many ascomycetes form associations with plants as endophytes or as members of lichens. Taxonomically, Ascomycota represents a major fungal lineage alongside Basidiomycota, together encompassing the majority of described fungi.