Discussion

The present study describes three novel species of Penicillium section Lanata-Divaricata—P. longyangense, P. longlingense, and P. zhenyuanense—from agricultural soils in mountainous areas of Yunnan Province, China. Section Lanata-Divaricata is a species-rich lineage within Penicillium subgenus Aspergilloides. Recent taxonomic revisions have refined the circumscription of this section and established a series-level infrasectional framework based primarily on multilocus phylogenetic relationships (Houbraken et al. 2020; Visagie et al. 2024). Species delimitation in this group generally requires an integrative approach because morphological characters may overlap among closely related taxa. Accordingly, the taxonomic conclusions of this study were based on congruent evidence from multilocus phylogenetic analyses and cultural and micromorphological characters.

Southwestern China, particularly Yunnan and adjacent areas, represents a hotspot for the discovery of new Penicillium species, yet Yunnan itself remains substantially undersampled, indicating that considerable Penicillium diversity remains to be uncovered in its soil ecosystems (Rong et al. 2016; Diao et al. 2019; Doilom et al. 2020; Xu et al. 2022; Wang et al. 2023; Song et al. 2024; Liang et al. 2024, 2025). Against this regional background, the three taxa described here help fill an important gap in knowledge of the diversity of section Lanata-Divaricata in Yunnan and warrant rigorous evaluation of their taxonomic distinctness.

To assess this taxonomic distinctness, multilocus phylogenetic analyses based on the ITS, BenA, CaM and RPB2 loci provided robust topological support for delimiting the eight isolates as three phylogenetically distinct species. Because ITS often provides limited resolution among closely related Penicillium species, protein-coding loci such as BenA, CaM and RPB2 are commonly used in combination, and species boundaries are not generally defined by a fixed level of sequence divergence at a single locus (Schoch et al. 2012; Visagie et al. 2014; Houbraken et al. 2020). In the present study, sequence similarities between the proposed species and their closest relatives remained high at some individual loci, ranging from 96.65% to 99.75% across the four loci (Table 2). Nevertheless, the concatenated four-locus dataset resolved all eight isolates into three independent monophyletic lineages, each represented by at least two isolates and receiving full support under both maximum likelihood and Bayesian inference (MLBS/BPP = 100%/1.00; Fig. 1). Penicillium longyangense, P. longlingense and P. zhenyuanense were clearly separated from their respective closest relatives, P. koreense, P. daleae and P. bissettii, and all three sister-group relationships were also fully supported (MLBS/BPP = 100%/1.00; Fig. 1). These phylogenetic relationships were congruent with diagnostic cultural and micromorphological differences. Penicillium longyangense differs from P. koreense KACC 47721T mainly in its slower growth on CYA and MEA, paler and more sparsely sporulating colonies, and generally shorter conidiophores and narrower phialides. P. longlingense differs from P. daleae CBS 211.28T principally in its slower growth on CYA and MEA, absence of exudates and soluble pigments, and globose to subglobose conidia. P. zhenyuanense differs from P. bissettii CBS 140972T mainly in its markedly slower growth, sparse sporulation, predominantly monoverticillate penicilli and shorter, smooth-walled conidiophores. Therefore, the recognition of P. longyangense, P. longlingense and P. zhenyuanense is not based on sequence divergence percentages alone, but on combined evidence from multilocus phylogenetic placement, representation by multiple isolates and diagnostic phenotypic differences. This taxonomic strategy is consistent with recent systematic studies of section Lanata-Divaricata, in which morphological characters and multilocus molecular data are jointly used as the principal criteria for species delimitation (Xu et al. 2022; Nóbrega et al. 2024; Liang et al. 2025; Supapongsri et al. 2025).

Species of Penicillium section Lanata-Divaricata have been recovered from diverse habitats, including acidic soils, coastal tidal flats, freshwater sediments, cave substrates, mangrove ecosystems, plant rhizospheres and bulk soils (Diao et al. 2019; Xu et al. 2022; Torres-Garcia et al. 2022; Nóbrega et al. 2024; Liang et al. 2025; Supapongsri et al. 2025). In the present study, the three novel taxa were isolated from agricultural soils in Baoshan and Pu’er, Yunnan Province. Although regional surveys have reported acidic or variable soil pH conditions in Longling, Longyang and Pu’er (Baoshan Agriculture and Rural Affairs Bureau 2021; Hu et al. 2022; Zhou et al. 2024), these regional data do not represent direct measurements at the sampling sites. Because soil pH, organic matter content, nutrient availability and other physicochemical properties were not measured in situ, any proposed associations of the new species with acidic or organic matter-rich soils, as well as any inferences regarding niche differentiation, remain speculative and require verification.

Some Penicillium strains have been associated with nutrient mobilization, plant–fungus interactions, tolerance to acidic or metal-stressed soil conditions, and the production of diverse secondary metabolites (Doilom et al. 2020; El Hajj Assaf et al. 2020; Suraby et al. 2023; Dhandapani et al. 2024). However, no functional assays were conducted for the three new species in the present study. Consequently, their potential roles in phosphate solubilisation, acid tolerance, secondary metabolite production and plant-associated interactions remain unverified. Future studies should expand sampling across cultivated, semi-natural and natural habitats, integrate site-specific analyses of soil pH, organic matter content, nutrient availability, moisture and texture, and conduct controlled functional assays, including assays of pH tolerance, phosphate solubilization and plant–fungus interactions, together with extrolite profiling. These approaches will help clarify the habitat distributions, environmental adaptability and potential ecological functions of P. longyangense, P. longlingense and P. zhenyuanense.

In conclusion, P. longyangense, P. longlingense and P. zhenyuanense are formally established as three novel species of Penicillium section Lanata-Divaricata. The present work highlights cultivated soils in Yunnan as a largely underexplored reservoir of soil-borne Penicillium diversity, and further systematic surveys across the region are likely to reveal additional undescribed Penicillium taxa and improve our understanding of the biogeography of this genus in southwestern China.