Multigene-based establishment of a novel Pleosporales family (Leandriaceae) and neotypification of Leandria momordicae Rangel.

Abstract

Leandria momordicae Rangel is the etiological agent of net spot, which is a very important disease of cucumber (Cucumis sativus), chayote (Sicyos edule), and in other Cucurbitaceae species. Although this pathogen was described more than a century ago infecting Momordica charantia, its taxonomic positioning has not yet been clarified. Moreover, a standard isolate of this fungus is not available in any reference mycological collection. In this context, the aims of the present work were (i) to clarify the taxonomic position of the fungus via morphological and phylogenetic analyses; (ii) to deposit a neotype of L. momordicae in a public mycological collection; (iii) to provide the first DNA sequences of the pathogen in GenBank. The morphometrical characteristics of distinct L. momordicae isolates were similar to those originally described. The phylogenetic analyses were carried out using information of five genomic regions. Using the BLASTn algorithm, it was observed that the L. momordicae-derived sequences displayed higher identity levels to fungal sequences of the order Pleosporales, which were subsequently included in the analyses. All sequences from the nine isolates of L. momordicae grouped within a single phylogenetic clade distinct from the other taxa in Pleosporales. Therefore, it is suggested the establishment of a new family of Pleosporales to include L. momordicae to which the name Leandriaceae is proposed. In addition, an ex-neotype and a neotype were illustrated and deposited in the Herbarium of the Federal University of Viçosa (VIC4754) and in the culture collection "Octávio Almeida Drummond" (COAD3403). The present study reinforces the view that many "hidden" fungal taxa are yet to be discovery under Neotropical conditions.