The ascomycetes include fungi that cause many common moulds and mildews, as well as plant pathogens, and a genus called Saccharomyces that contains the yeasts used in baking and brewing. Ascomycetes are also the fungal partner for 98% of all lichens.
This order shows much variation in appearance as it contains the morels, truffles, and cup fungi. Fruiting bodies range from dull to bright colours, are edible or poisonous, and live as saprobes, parasites, or as mycorrhizal symbionts. Three genera in this group, Ascobolus, Saccobolus, and Lasiobolus, occur in the High Arctic and are coprophilous decomposers, which play a pivotal role in the recycling of herbivore dung. Members of the family Tuberaceae live underground and include the truffles, considered a culinary delight to some. Their fruiting body, which is solid so to aid spore dispersal, is the edible part and releases an odour that attracts animals. Animals will then unearth the fungal ball, consume it, and deposit the spores elsewhere in their dung. Many members of this group also form ectomycorrhizal relationships with dwarf trees in the Arctic. The Inuit, who rarely eat other fungi, have eaten the truffle, Geopora arenosa, for many years.
This group of fungi are decomposers, feeding on dung or decaying plant remains. Species in the genera Sordaria and Podospora fruit on herbivore dung, and shoot their spores toward sunlight using a phototropic neck. Species found in the Arctic include Gelasinospora tetrasperma, Podospora tetraspora, and Sordaria fimicola.
Species in this group are obligate parasites on the leaves of flowering plants, and are collectively known as the powdery mildews. Infected plants develop a dry, white, powdery coating on their leaves, shoot tips and flowers. Powdery mildews often cause stunted or distorted growth of the host plant and decrease flowering. Most powdery mildews are very host specific. Many members of the Erysiphales are found in the Arctic, including species in the genera Podospharea, Microsphaera, and Erysiphe.