Phylogenetic placement and reassessment of Asperisporium pongamiae as Pedrocrousiella pongamiae gen. et comb. nov. (Mycosphaerellaceae).

Abstract

The leaf spot disease of Pongamia pinnata caused by an asperisporium-like asexual morph, which is usually referred to as Asperisporium pongamiae, is quite common during monsoon seasons in India. Phylogenetic analyses, based on LSU and rpb2 sequence data, and blast searches using ITS sequence data, revealed that this ascomycete forms a lineage within Mycosphaerellaceae distant from all other generic lineages. Pedrocrousiella gen. nov., with P. pongamiae comb. nov., based on Fusicladium pongamiae (≡ A. pongamiae), as type species is introduced for this lineage. This species has been considered the asexual morph of Mycosphaerella pongamiae (≡ Stigmatea pongamiae). However, this connection is unproven and was just based on the occasional association of the two taxa in some collections. Several attempts to induce the formation of a sexual morph in culture failed, therefore the putative connection between these morphs could not be confirmed. Asperisporium pongamiae-pinnatae is reduced to synonymy with P. pongamiae. Asperisporium pongamiae-pinnatae was introduced because of the wrong assumption that F. pongamiae had been described on another host, Pongamia globosa. But Fusicladium pongamiae was actually described in India on Pongamia glabra, which is a synonym of P. pinnata, and hence on the same host as Asperisporium pongamiae-pinnatae. Pedrocrousiella pongamiae clusters in a clade containing Distocercospora, Clypeosphaerella, and "Pseudocercospora" nephrolepidicola, a species which is not congeneric with Pseudocercospora. Phylogenetically, Pedrocrousiella is distant from the Asperisporium s. str. clade (type species A. caricae), which is more closely related to Amycosphaerella, Pseudocercosporella, Distomycovellosiella and Nothopassalora. Citation: Rajeshkumar KC, Braun U, Groenewald JZ, Lad SS, Ashtekar N, Fatima S, Anand G (2021). Phylogenetic placement and reassessment of Asperisporium pongamiae as Pedrocrousiella pongamiae gen. et comb. nov. (Mycosphaerellaceae). Fungal Systematics and Evolution 7: 165-176. doi: 10.3114/fuse.2021.07.08.