Morphological and molecular characterization of Leptomelanconium allescheri associated with necrotic lesions on Pinus mugo needles in the Polish Tatra Mountains

Leptomelanconium allescheri was identified for the first time in Poland in 2016 in the Tatra Mts. on Pinus mugo needles. It produced numerous conidiomata on necrotic lesions on live needles. In our study, we provide detailed characteristics of disease symptoms and describe morphology of the structures of the fungus. The shape and size of macroconidia are proven to be more variable in vitro than in situ. The malt extract agar colonies of the fungus obtained from germinating macroconidia are described for the first time. Our observations prove also that, apart from macroconidia, L. allescheri produces in vitro unicellular, hyaline microconidia, 3.5–10 × 1.8–5.0 μm in size, the previously unknown aspect in the development cycle of this species. The BLAST search with ITS and LSU sequences of L. allescheri resulted in the closest match with Cenangium acuum accessions (94%–95% and 99%, respectively). Two gene based, LSU plus ITS, phylogenetic positioning of L. allescheri proves that it belongs to Pezizomycotina, Helotiales. Further, on family level, placement of L. allescheri, as well as its two closest species C. acuum and Piceomphale bulgarioides, remains undefined. The L. allescheri barcode sequences (accession numbers: ITS— MF573935 , LSU— MF573936 , IGS— MF573937 ) and cultures were submitted to NCBI GenBank and CBS Utrecht, The Netherlands culture collection.