Morphology and phylogeny reveal two new species of pestalotioid fungi associated with hawthorn in Northeast China

Hawthorn (Crataegus pinnatifida), a valuable fruit tree with significant economic and ecological importance, is cultivated across numerous regions in China. In this study, we describe two novel saprobic fungi Sporocadus changchunensis and S. crataegicola. The novelty of these species is supported by both morphological characteristics and analyses using maximum likelihood (ML) and Bayesian inference (BI).

Sporocadus crataegicola formed a distinct clade from S. changchunensis and S. rotundatus with 98 % ML and 1.00 BPP statistical support, and the morphological character of S. crataegicola is remarkable in its distinguishable shape of ascospores and fewer septa. Sporocadus changchunensis differs from S. italicus, which was also found on Crataegus, by its narrower ostiolar canal, wider hamathecium, and smaller asci. The internal transcribed spacer (ITS) region, the large subunit (LSU) of ribosomal DNA, the RNA polymerase II subunit (rpb 2), the translation elongation factor 1 - alpha (tef 1 - α), and β-tubulin (tub 2) genes were used for the phylogenetic analyses.

An inoculation experiment was also performed to determine the possibility of latent pathogens on C. pinnatifida. The inoculation experiment showed that the species caused black spots on the mature leaves of hawthorn. We hypothesize that saprobes possess potential pathogenic ability that may lead to the occurrence of plant diseases under various circumstances.

This study also extends the knowledge of the host range and geographic distribution of Sporocadus species in China.