Phomopsis stem canker is economically important sunflower disease that caused by multiple Diaporthe species. Recent investigations resulted in the resolution that there are at least 13 Diaporthe species that can infect sunflower. A comprehensive analysis of the biodiversity and geographic distribution of Diaporthe species in Russia, particularly those that infect sunflower, has not been undertaken. For this study, 16 Diaporthe isolates were obtained from samples of stem canker and visually healthy seeds of Helianthus annuus from northwestern, central European, southern European Russia, North Caucasus, and the Urals in 2016–2019. The aim of this study was to identify these Diaporthe isolates based on morphology and sequence analyses of the nuclear ribosomal internal transcribed spacer (ITS) region, partial calmodulin (cal), DNA-lyase (apn2), histone H3 (his3), translation elongation factor-1α gene (tef1), and ß-tubulin (tub2) genes. The phylogenetic reconstruction revealed well-supported monophyletic clades corresponding to six Diaporthe species: D. eres, D. gulyae, D. helianthi, and D. phaseolorum. Two new species were described: Diaporthe monetii sp. nov. and Diaporthe vangoghii sp. nov. The isolates of D. gulyae and D. phaseolorum collected represent the first records of these species in Russia.

A Fusarium species associated with sunflower based on multilocus genealogy, morphological, physiological, ecological, mating type, and mycotoxin production data is formally described as the newly discovered species Fusarium bilaiae. The F. bilaiae strains formed a genealogically exclusive lineage within the African clade of the F. fujikuroi species complex. Comparison of morphological characteristics of F. bilaiae strains with those of the closely related F. phyllophilum strain NRRL 13617 revealed similarities in the main micromorphology of both species: production of numerous one-celled microconidia in false heads and short chains on monophialides and polyphialides and the absence of macroconidia and sporodochia. There was a slight but significant distinction between the two species when the strains were grown on different agar media, as well as in the shape and width of microconidia. Fusarium bilaiae strains isolated from symptomatic sunflower were not pathogenic to members of the Asteraceae tested; apparently, they live as saprophytes or endophytes in sunflower tissues. A difference between the strains of the two species in the production of mycotoxins was demonstrated with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) analysis. On autoclaved rice, F. bilaiae did not produce fumonisins and beauvericin but produced moniliformin, whereas F. phyllophilum produced all these mycotoxins. A polymerase chain reaction (PCR) assay specific for mating type alleles identified F. bilaiae as a putative heterothallic species with MAT1-1 and MAT1-2 idiomorphs, but laboratory crosses were unsuccessful. Determining the area and host range of the new endophytic species F. bilaiae is a priority for future research.

Prunus mandshurica is a rare species of the Russian Far East; it is cultivated for fruits and as an ornamental tree. The objective was to determine the fungi associated with young shoots of the Manchurian apricot, which is an important biotic factor for plant viability and productivity. Fungi were isolated by incubation of shoot fragments (unsterilized or surface-sterilized) on a growth medium and identified according to their cultural and morphological characteristics. Diaporthe eres and Nothophoma quercina isolates were identified by multilocus phylogenetic analysis (apn2, cal, tef1-α, tub2 for D. eres, and ITS, rpb2, tub2 for N. quercina). In total, 12 species (Alternaria alternata, A. tenuissima, Aureobasidium pullulans, Cladosporium cladosporioides, C. herbarum, D. eres, Epicoccum nigrum, Fusarium graminearum, F. oxysporum, N. quercina, Sarocladium strictum, and Tripospermum myrti) and one genus (Gliocladium sp.) were found. Alternaria alternata, N. quercina, and D. eres were the most frequent species of the shoots. Alternaria tenuissima and F. oxysporum were also frequent in some collections, while all other species were rare or occasional in occurrence. Molecular analysis of D. eres and N. quercina revealed redundancy of some species within the D. eres species complex and the genus Nothophoma. This is the first report on the fungal inhabitants of asymptomatic shoots of P. mandshurica. Nothophoma quercina was identified in Russia for the first time.

Alternaria is a large genus within Pleosporaceae and consists of fungi that have up to recently been considered to be 15 separate genera, including Ulocladium. The majority of Ulocladium species after incorporation into Alternaria were placed in three sections: Ulocladioides, Pseudoulocladium, and Ulocladium. In this study, phylogeny of 26 reference strains of 22 species and 20 Russian Ulocladium-like isolates was recovered. The partial actin gene (act), Alternaria major allergen (alta1), calmodulin (cal), glyceraldehyde-3-phosphate dehydrogenase (gapdh), RNA polymerase II second largest subunit (rpb2), and translation elongation factor 1-α (tef1) were sequenced for Russian isolates. All these fungi were examined using multilocus phylogenetic analysis according to the genealogical concordance phylogenetic species recognition (GCPSR) principle and the coalescent-based model Poisson tree processes (PTP, mPTP) and evaluated for the presence of recombination. All strains were combined into two clades that corresponded to the Pseudoulocladium and Ulocladioides sections. The Pseudoulocladium clade included four reference strains and nine local isolates and considered to be a single species, whereas the Ulocladioides section comprises 11 species, instead of 17 names previously adopted. Nine species were abolished by joining four other species. Species A. atra and A. multiformis were combined into the single species A. atra. Five species, A. brassicae-pekinensis, A. consortialis, A. cucurbitae, A. obovoidea, and A. terricola, were united in the species A. consortialis. Alternaria heterospora and A. subcucurbitae were combined into one species, A. subcucurbitae. Alternaria aspera, A. chartarum, A. concatenata, and A. septospora were combined into a single species, A. chartarum. Also, amplification with two different primer sets was performed to define mating-type locus 1 (MAT1) idiomorph. All studied isolates were heterothallic, contradicting some prior studies. Twenty Russian Ulocladium-like isolates were assigned to five species of two sections, A. atra, A. cantlous, A. chartarum, A. consortialis, and A. subcucurbitae. Species A. cantlous and A. subcucurbitae were found in Russia for the first time.