Distinguishing individual Russula species has been difficult due to extensive phenotypic plasticity and obscure morphological and anatomical discontinuities. Due to highly similar macroscopic features, such as the presence of a red-cap, species identification within the Russula subgenus Amoenula is particularly difficult. Three species of the subgenus Amoneula have been reported in Korea. We used a combination of morphology and three molecular markers, the internal transcribed spacer (ITS), 28S nuclear ribosomal large subunit (LSU), and RNA polymerase II gene (RPB2), for identification and study of the genetic diversity of Russula subgenus Amoenula in Korea. We identified only two species in Korea (R. mariae and R. violeipes); these two species were indistinguishable according to morphology and LSU, but were found to be reciprocally monophyletic species using ITS and RPB2. The markers, ITS, LSU, and RPB2, have been tested in the past for use as DNA barcoding markers, and findings of our study suggest that ITS and RPB2 had the best performance for the Russula subgenus Amoneula.

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Distinguishing individual Russula species can be very difficult due to extensive phenotypic plasticity and obscure morphological and anatomical discontinuities. In this study, we use the internal transcribed spacer (ITS) and 28S nuclear ribosomal large subunit (LSU) markers to identify and study the genetic diversity of species in the Russula subgenus Compacta in Korea. We focus on two morphologically similar species that are often misidentified for each other: R. nigricans and R. subnigricans. Based on molecular phylogenetic analyses, we identify three subgroups of R. nigricans, with two from Asia and one from Europe/North America. Surprisingly, we find Korean R. subnigricans are more closely related to R. eccentrica from North America than the type specimen of R. subnigricans from Japan. These molecular data, along with habitat data, reveal that Korean R. subnigricans had previously been misclassified and should now be recognized as R. eccentrica. Both ITS and LSU exhibit high interspecific and low intraspecific variation for R. eccentrica, R. nigricans, and R. subnigricans. These markers provide enough resolutional power to differentiate these species and uncover phylogeographic structure, and will be powerful tools for future ecological studies of Russula.

White-rot fungi of the genus Bjerkandera are cosmopolitan and have shown potential for industrial application and bioremediation. When distinguishing morphological characters are no longer present (e.g., cultures or dried specimen fragments), characterizing true sequences of Bjerkandera is crucial for accurate identification and application of the species. To build a framework for molecular identification of Bjerkandera, we carefully identified specimens of B. adusta and B. fumosa from Korea based on morphological characters, followed by sequencing the internal transcribed spacer region and 28S nuclear ribosomal large subunit. The phylogenetic analysis of Korean Bjerkandera specimens showed clear genetic differentiation between the two species. Using this phylogeny as a framework, we examined the identification accuracy of sequences available in GenBank. Analyses revealed that many Bjerkandera sequences in the database are either misidentified or unidentified. This study provides robust reference sequences for sequence-based identification of Bjerkandera, and further demonstrates the presence and dangers of incorrect sequences in GenBank.

A new species belonging to Lactarius subg. Plinthogalus was discovered during a long-term project on the diversity of Korean Lactarius. This species is proposed here as Lactarius cucurbitoides. The status of L. cucurbitoides as a new species is supported by molecular data and morphological features. Phylogenetic analysis based on internal transcribed spacer (ITS) sequences shows that L. cucurbitoides is closely related to L. subplinthogalus, L. friabilis, and L. oomsisiensis, with pairwise distances of 2.8-4.3%. Morphological characters of L. cucurbitoides that distinguish it from these closely related species are a pale yellow to pale orange colored pileus and non-discoloration of white latex. The new species is described and illustrated in the present paper.