Rufoboletus N.K. Zeng & Zhi Q. Liang, gen. nov.

Index Fungorum number: IF 559490; Mycobank number: MB 559490; Facesoffungi number: FoF 14856.

Etymology – Lain “rufo-”, meaning the hymenophore and context of the new genus turning red when injured.

Basidiomes stipitate-pileate with tubular hymenophore. Pileus hemispherical, convex to applanate, surface tomentose; context thick, white, changing blue quickly, then turning red and finally black when injured. Hymenophore thin, yellow, changing blue quickly, then turning red and finally black when injured. Stipe central, subcylindrical; surface without reticulations; context white, changing blue quickly, then turning red and finally black when injured. Basal mycelium white. Basidiospores subfusiform to ellipsoid, smooth. Pleuro- and cheilocystidia present. Pileipellis a trichoderm. Clamp connections absent.

Type species – Rufoboletus hainanensis (N.K. Zeng, Zhi Q. Liang & S. Jiang) N.K. Zeng & Zhi Q. Liang.

Notes – Rufoboletus is characterized by a large basidiome, a pileus with thick context and thin hymenophore, a blue-red–black color change of hymenophore and context when injured, a stipe without reticulations, and smooth basidiospores. In previous studies, species of Rufoboletus was placed into the genus Butyriboletus (Liang et al. 2016; Chai et al. 2019). However, species of Butyriboletus has a blue (without red) color change of hymenophore and context when injured, and a stipe with obvious reticulations. The thick context and thin hymenophore characterized by Rufoboletus are also reminiscent of the genus Baorangia; however, species of Baorangia has a blue (without red) color change of hymenophore and context when injured, and a stipe usually with reticulations (Wu et al. 2016b; Zhang et al. 2021b).

Phylogenetically, the type species of Rufoboletus, viz. B. hainanensis and Boletus sp. (KUN-HKAS 52525) formed an independent generic clade (Fig. 1), which was labeled as “hainanensis clade” by Biketova et al. (2022) and also supported by the phylogenetic analyses of Gelardi et al. (2015), Liang et al. (2016), Fu et al. (2022) and Wang et al. (2022a, b).

Figure 1 – Phylogenetic placement of Rufoboletus inferred from a four-locus (28S, ITS, TEF1, and RPB2) dataset using RAxML. BS≥50% and PP≥0.95 are indicated above or below the branches as RAxML BS/PP

Species