Basidiomycota R.T. Moore (1980) constitute a large and diverse phylum of the kingdom Fungi consisting, as of December 2020, of 1948 genera, in four subphyla, 18 classes, 68 orders, 241 families and 41,270 species (He et al. 2019). The phylum is estimated to have diverged around 530 million years ago (Zhao et al. 2017). Basidiomycota include macrofungi such as mushrooms, puffballs, and bracket fungi as well as microfungi such as yeasts, smuts and rusts (Kurtzman et al. 2015; Zhao et al. 2017). Generally speaking, Basidiomycota reproduce sexually by forming exospores (basidiospores) on the outside of cells called basidia producing 2 to 8 basidiospores and they have walled, septate hyphae with specialized septal pores (dolipore septa), though there are numerous exceptions (Yang, 2011; He et al. 2019; Zhao et al. 2017). The phylum Basidiomycota was shown to be a monophyletic group sister to Ascomycota (James et al. 2006; Hibbett et al. 2007). A higher-level classification of Basidiomycota was published around ten years ago, based mainly on a series phylogenetic studies, such as the Deep Hypha and AFTOL projects (Blackwell et al. 2006; James et al. 2006; Hibbett et al. 2007; Lutzoni et al. 2004). However, there has been considerable advances since this time and the classification have been updated. For example, the class Entorrhizomycetes has been split from Basidiomycota and raised to phylum Entorrhizomycota. New classes (Malasseziomycetes, Moniliellomycetes, Spiculogloeomycetes, Tritirachiomycetes), and new orders (Holtermanniales, Trichosporonales, Golubeviales, Robbauerales, Unilacrymales, Amylocorticiales, Jaapiales, Stereopsidales and Lepidostromatales) have been introduced (Binder et al. 2010; Boekhout et al. 2011; Schell et al. 2011; Wuczkowski et al. 2011; Shirouzu et al. 2013; Hodkinson et al. 2014; Sjökvist et al. 2014; Weiss et al. 2014; Wang et al. 2014, 2015).
Currently, Basidiomycota includes three major clades—Agaricomycotina (mushrooms, jelly fungi, bracket fungi and others), Pucciniomycotina (rusts), and Ustilaginomycotina (smuts and others) (Hibbett et al. 2007)—as well as Wallemiomycotina (Zhao et al. 2017). Agaricomycotina (30,788 species) embrace most of the species in Basidiomycota and includes three classes, 29 orders, 150 families and 1514 genera. Russula, Cortinarius and Entoloma are the top three genera in species diversity in Agaricomycotina, and are estimated to have 3000, 2250 and 1800 species, respectively. Pucciniomycotina has a high diversity especially with respect to higher-level taxa which embraces more than half the classes in Basidiomycota (10 out of 18). The top three genera in species diversity are Puccinia, Uromyces and Aecidium with the estimated species numbers of 3300, 1500 and 800 respectively. Ustilaginomycotina is estimated to have 1805 species which includes four classes, 15 orders, 42 families and 128 genera. Ustilaginomycetes with 1185 species is the largest group in Ustilaginomycotina. Malasseziomycetes and Moniliellomycetes, the only two new classes recognized in the Basidiomycota since 2008, include an estimated 32 species. The top three genera in terms of species numbers are Sporisorium, Tilletia and Ustilago with 195, 179 and 170 species, respectively. Wallemiomycotina is a recently recognized subphylum (Zhao et al. 2017c) with 12 species estimated in a single class, two orders and two families. The divergence times of the subphyla in Basidiomycota are 406–430 Mya, classes are 211–383 Mya, and orders are 99–323 Mya (He et al. 2019). Families of Agaricomycotina diverged during 27–178 Mya, Pucciniomycotina diverged during 85–222 Mya and those from Ustilaginomycotina 79–177 Mya.