Prevalent weeds collected from cucurbit fields in Northeastern Brazil reveal new species diversity in the genus Monosporascus

Abstract

[EN] Fungal species belonging to the ascomycete genus Monosporascus have no known asexual morph and the ascocarp is a globose perithecium where asci develop, containing from 1 to 6 spherical ascospores, depending on the species. Monosporascus cannonballus is the most well-known species of the genus, and an important root pathogen associated with the vine decline of melon and watermelon crops worldwide. The aim of the present study was to characterise a collection of 35 Monosporascus-like isolates recovered from roots of two weed species prevalent in cucurbit growing fields in Northeastern Brazil: Boerhavia diffusa and Trianthema portulacastrum. These isolates were identified based on DNA sequences of the Internal Transcribed Spacer regions (ITS) of the nuclear rDNA, part of the translation elongation factor gene (tef-1), part of the -tubulin gene (tub), part of the nuclear small subunit (SSU) rDNA and part of the large subunit (LSU) rDNA. Five Monosporascus species, namely Monosporascus brasiliensis, Monosporascus caatinguensis, Monosporascus mossoroensis, Monosporascus nordestinus and Monosporascus semiaridus, are newly described. Monosporascus brasiliensis, M. nordestinus and M. semiaridus were isolated from both weed species, while M. caatinguensis only from T. portulacastrum and M. mossoroensis only from B. diffusa. The present study confirms that Monosporascus spp. can colonise roots of very diverse hosts, even without causing noticeable disease symptoms, and reveals that the diversity of species in the genus Monosporascus is potentially greater than previously expected.