Taxonomic investigation and re-assessment of some Cercosporoid fungi from India
Raghvendra Singh1* and Shambhu Kumar2
1Centre of Advanced Study in Botany, Institute of Science, Banaras Hindu University, Varanasi, U.P., India 221005
2Forest Pathology Department, KSCSTE-Kerala Forest Research Institute, Peechi, Thrissur, Kerala, India 680653
*Email: firstname.lastname@example.org, email@example.com
Clypeosphaerella indica was discovered on living leaves of Mallotus philippensis (Euphorbiaceae). Clypeosphaerella is morphologically similar to species of Mycosphaerella s.lat., differs by having the thicker upper wall of the ascomata, resembling a pseudoclypeus. Additionally, this genus is phylogenetically distinct from other mycosphaerella-like fungi. The isolate’s morphology has similar diagnostic characters to those of Passalora and the phylogenetic analysis based on ITS placed the species in a single-strain lineage closely related to Pseudocercospora. In the present study, based on a multigene analysis (LSU-RPB2-ITS), this strain clusters among the species of Clypeosphaerella, which is closely related to Pseudocercospora. The main issue is that the previously described species in this genus, C. sticheri and C. quasiparki, are only known by their sexual morph and C. calotropidis is only known from its asexual morph. Based on the molecular and morphological data, we propose a new species in Clypeosphaerella as C. indica.
Another new hyaline cercosporoid fungus was discovered on living leaves of Tinospora cordifolia (Menispermaceae). Based on multigenes (LSU-RPB2-ITS) phylogenetical analysis, this strain represents a new lineage within Neocercosporella. Hence, a new species N. indica is proposed. Superficially, the colourless nature with thickened and darkened loci and hila make it closer to Cercosporella, but differs in having terminal and intercalary conidiogenous cells and weak catenation in conidia. Phylogenetically, Neocercosporella is distant from the Cercosporellas. str. clade (type species C. virgaureae). Phylogenetic examinations and ultrastructure of conidiogenous loci and hila of conidia of both N. indica andN. peristrophes indicate that both are congeneric. Neocercosporella can be easily distinguished from closely related members of ramularioid complex namely Cercosporella, Pseudocercosporella and Ramularia, based on the ultrastructure of their conidiogenous loci. Neocercosporella has conical loci with very small rim-like depressions on the top encircling a small, flat and protuberant-like structure. Neocercosporella produces terminal and intercalary conidiogenous cells and weak catenation of conidia.
Other two undescribed species of Zasmidium were discovered on Cassia fistula (Fabaceae) and Meyna laxiflora (Rubiaceae). These are characterized by having planate conidial scars, verruculose superficial hyphae, and solitary to rarely catenate and usually rough-walled conidia. Verruculose superficial hyphae and rough-walled conidia are characters shared by both Stenella and Zasmidium. Both these genera can be easily distinguished from each other only based on molecular analyses. The genus Stenella clusters within the Teratosphaeriaceae and characterized by pileate conidiogenous loci, while Zasmidium is distinguished by having planate Cercospora-like conidiogenous loci and belongs to the Mycosphaerellaceae.
KEYWORDS: Anamorph; Ascomycota; Dothideomycetes; New taxa; Nomenclature; Phylogeny