The forma specialis concept has been a cornerstone in Fusarium phytopathology for 85 years, classifying pathogens based on host specificity. However, its validity as a natural and practical framework has been increasingly questioned. In this study, we critically re-evaluate the forma specialis concept through an extensive survey of Fusarium wilt diseases across 37 crop hosts from 23 provinces of China. Through multi-locus phylogenetic analyses, morphological assessments, and pathogenicity tests on 659 strains isolated from 171 diseased samples, we identified 46 Fusarium species, including seven newly described taxa, and uncovered extensive cross-host pathogenicity, with up to 21 species associated with the same wilt disease. In addition, 57% of samples exhibited multiple species co-infections, revealing significant inconsistencies with the forma specialis framework. These findings challenge the long-standing paradigm of host specificity in Fusarium pathogens and advocate for a shift of perspective to a “pathobiome” framework, where disease dynamics are largely driven by community-level interactions rather than single-pathogen relationships. Applying these conceptual advances to Fusarium wilt research could fundamentally transform our comprehension of host-pathogen relationships and facilitate the development of more ecologically sustainable disease management approaches.

Rust fungi in the order Pucciniales represent one of the largest groups of phytopathogens, which occur on mosses, ferns to advanced monocots and dicots. Seven suborders and 18 families have been reported so far, however recent phylogenetic studies have revealed para- or polyphyly of several morphologically defined suborders and families, particularly in Melampsorineae. In this study, a comprehensive phylogenetic framework was constructed based on a molecular phylogeny inferred from rDNA sequences of 160 species belonging to 16 genera in Melampsorineae (i.e. Chrysomyxa, Cerospora, Coleopuccinia, Coleosporium, Cronartium, Hylospora, Melampsora, Melampsorella, Melampsoridium, Milesina, Naohidemyces, Pucciniastrum, Quasipucciniastrum, Rossmanomyces, Thekopsora, Uredinopsis). Our phylogenetic inference indicated that 13 genera are monophyletic with strong supports, while Pucciniastrum is apparently polyphyletic. A new genus, Nothopucciniastrum was therefore established and segregated from Pucciniastrum, with ten new combinations proposed. At the family level, this study further demonstrates the importance of applying morphologies of spore-producing structures (basidia, spermogonia, aecia, uredinia and telia) in higher rank taxonomy, while those traditionally applied spore morphologies (basidiospores, spermatia, aeciospores, urediniospores and teliospores) represent later diverged characters that are more suitable for the taxonomy at generic and species levels. Three new families, Hyalopsoraceae, Nothopucciniastraceae and Thekopsoraceae were proposed based on phylogenetic and morphological distinctions, towards a further revision of Pucciniales in line with the phylogenetic relationships.

A new rust genus, Quasipucciniastrum, typified by Q. agrimoniae sp. nov., is proposed based on distinct morphological characters and phylogenetic placement. This genus is characterised by its uredinial ostiolar peridial cells with rough surface and sessile, multicellular teliospores with apparently thickened apical wall. Molecular phylogenetic analyses using internal transcribed spacer regions and intervening 5.8S nrRNA gene (ITS) and the large subunit (LSU) rDNA revealed that this genus is sister to the genus Cronartium (Cronartiaceae), but morphologically it is distinct from Cronartium in the sessile teliospores that are divided by vertical septa. Morphologically, Quasipucciniastrum should be compared to Pucciniastrum (Pucciniastraceae) in its multicellular teliospores, but they were phylogenetically distant.

The generic concept of Phyllosticta has undergone substantial changes since its establishment in 1818. The existence of conidia with a mucilaginous sheath and an apical appendage is synapomorphic for Phyllosticta species, which has been shown in recent molecular phylogenetic studies. Thus a natural classification of Phyllosticta species should emphasize above morphological characters. Many names in Phyllosticta, both published in the scientific literatures and in publically accessible databases, need updating. In China, more than 200 species names in Phyllosticta have been recorded, of which, 158 species names are reviewed here based on their morphological descriptions and molecular data. Only 20 species of Phyllosticta are accepted from China. Other records of Phyllosticta refer to Phoma (89 records), Asteromella (14 records), Boeremia (9 records), Phomopsis (7 records) and Microsphaeropsis (1 record), with 19 names of uncertain generic classification. This work demonstrates an urgent need for the re-assessment of records of Phyllosticta worldwide.