Hyalokamalomyces: a novel Septoria-like genus in Mycosphaerellaceae based on polyphasic evidences

During a survey of foliicolous fungi in India, an interesting anamorphic fungal specimen was collected and isolated from diseased leaves of Cassia fistula . The fungus produced globose to subglobose, or acervular conidiomata, rarely pycnidial, that released creamy-white to light yellowish-brown conidial mass in creamy cirrhi on the host. Morphologically, the specimen resembles Cylindrosporium cassiae , previously placed in the family Ploettnerulaceae . However, its true generic affinity remained uncertain for a long time due to the absence of molecular sequence data and ultrastructural studies, and was therefore classified solely on morphological features. A polyphasic approach, incorporating morphological and cultural observations together with multi-locus phylogenetic analyses (LSU- RPB2 -ITS) and genealogical concordance phylogenetic species recognition, clarified its placement within the family Mycosphaerellaceae . Phylogenetic analyses confirmed that this specimen represents a distinct lineage or DNA sequence counterparts. Consequently, a new genus, Hyalokamalomyces , is proposed, with H. cassiae comb. nov. designated as the type species. Additionally, Cylindrosporium cassiae is recognized as a new synonym. Morphologically, Hyalokamalomyces closely resembled with Septoria and Septoria -like taxa; however, it can be readily distinguished by the ultrastructure of its conidiogenous loci and hila. In Hyalokamalomyces , the conidiogenous loci are flat or truncated and bear a small central conical depression, while the conidial base is truncated or occasionally slightly rounded, with hila showing a slight depression and a small conical structure corresponding to that of the loci. These unique ultrastructural features have not been reported in any genera within the Mycosphaerellaceae , nor in Septoria or Septoria -like species.