Morphological and molecular characterization of two graminicolous &lt;i&gt;Exserohilum&lt;/i&gt; species associated with cultivated rice and early barnyard grass from Sri Lanka

H S Ferdinandez,D Udayanga,N Deshappriya,M L A M S Munasinghe,D S Manamgoda

doi:10.4038/cjs.v49i5.7805

Morphological and molecular characterization of two graminicolous <i>Exserohilum</i> species associated with cultivated rice and early barnyard grass from Sri Lanka

H S Ferdinandez, D Udayanga + Show 3 more

Open Access

https://doi.org/10.4038/cjs.v49i5.7805

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Abstract

The genus Exserohilum (Order Pleosporales, Class Dothideomycetes) comprises plant pathogenic hyphomycetous fungi, associated with poaceous hosts. Although numerous pathogenic species of Exserohilum are known globally, only E. turcicum and E. rostratum have been reported from Sri Lanka. In the present study, samples showing the symptoms of leaf blight of Oryza sativa (cultivated rice) and sheath blight of Echinochloa oryzoides (early barnyard grass) were collected and causal agents were primarily identified as Exserohilum spp. based on morphological characters. Molecular phylogenetic analyses based on three loci namely, nuclear ribosomal internal transcribed spacer (ITS), partial glyceraldehyde 3-phosphate dehydrogenase (GPDH) and translational elongation factor (TEF-1α) were used to infer evolutionary relationships and accurate identification. These isolates from O. sativa and Echinochloa oryzoides were identified as Exserohilum rostratum and E. oryzicola respectively. Both records are novel plant-fungal associations from Sri Lanka based on available data. This study suggests the need for morphological and molecular reassessments of emerging and poorly known species of fungi associated with cereals, their wild relatives and other economically important hosts in Sri Lanka.

Highlights

The hyphomycetous fungi associated with grass hosts, previously known as “graminicolous Helmonthosporium species”, include six genera belonging to order Pleosporales namely Curvularia, Bipolaris, Exserohilum, Drechslera, Johnalcornia and Porocercospora (Manamgoda et al, 2012; Amaradasa et al, 2014; Tan et al, 2014; HernandezRestrepo et al, 2018)
This study suggests the need for morphological and molecular reassessments of emerging and poorly known species of fungi associated with cereals, their wild relatives and other economically important hosts in Sri Lanka
Species of this genus are frequently encountered as asexual morphs in nature, the sexual morphs were often obtained by mating compatible strains (Hernandez-Restrepo et al, 2018)

Summary

Introduction

The hyphomycetous fungi associated with grass hosts, previously known as “graminicolous Helmonthosporium species”, include six genera belonging to order Pleosporales namely Curvularia, Bipolaris, Exserohilum, Drechslera, Johnalcornia and Porocercospora (Manamgoda et al, 2012; Amaradasa et al, 2014; Tan et al, 2014; HernandezRestrepo et al, 2018). The sexual morph of Exserohilum was previously characterized under Setosphaeria (Leonard and Suggs, 1974). Species of this genus are frequently encountered as asexual morphs in nature, the sexual morphs were often obtained by mating compatible strains (Hernandez-Restrepo et al, 2018). Recent molecular phylogenetic assessments have resulted in considerable taxonomic refinements of numerous species in the genus Exserohilum. Based on molecular phylogenetic analysis, six formerly known taxa namely E. antillanum, E. gedarefense, E. leptochloae, E. longirostratum, E. macginnisii and E. prolatum were found to be conspecific with commonly encountered taxon E. rostratum (Hernandez-Restrepo et al, 2018). E. curvatum was synonymized with E. holmii, and E. fusiforme with E. oryzicola (Hernandez-Restrepo et al, 2018)

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