Abstract
Background Epicoccum nigrum Link (syn. E. purpurascens Ehrenb. ex Schlecht) is a saprophytic ascomycete distributed worldwide which colonizes a myriad of substrates. This fungus has been known as a biological control agent for plant pathogens and produces a variety of secondary metabolites with important biological activities as well as biotechnological application. E. nigrum produces darkly pigmented muriform conidia on short conidiophores on sporodochia and is a genotypically and phenotypically highly variable species. Since different isolates identified as E. nigrum have been evaluated as biological control agents and used for biocompound production, it is highly desirable that this species name refers to only one lineage. However, according to morphological and genetic variation, E. nigrum present two genotypes that may comprise more than one species.Methodology/Principal FindingsWe report the application of combined molecular (ITS and β-tubulin gene sequence analysis, PCR-RFLP and AFLP techniques), morphometric, physiological, genetic compatibility and recombination analysis to study the taxonomic relationships within an endophytic population that has been identified as E. nigrum. This combined analysis established two genotypes showing morphological, physiological and genetic divergence as well as genetic incompatibility characterized by colony inhibition, strongly indicating that these genotypes correspond to different species. Genotype 1 corresponds to E. nigrum while genotype 2 represents a new species, referred to in this study as Epicoccum sp.Conclusions/SignificanceThis research contributes to the knowledge of the Epicoccum genus and asserts that the classification of E. nigrum as a single variable species should be reassessed. In fact, based on the polyphasic approach we suggest the occurrence of cryptic species within E. nigrum and also that many of the sequences deposited as E. nigrum in GenBank and culture collection of microbial strains should be reclassified, including the reference strain CBS 161.73 sequenced in this work. In addition, this study provides valuable tools for differentiation of Epicoccum species.
Highlights
Based on the polyphasic approach we suggest the occurrence of cryptic species within E. nigrum and that many of the sequences deposited as E. nigrum in GenBank and culture collection of microbial strains should be reclassified, including the reference strain CBS 161.73 sequenced in this work
E. nigrum is mainly associated with the primary decomposition of plant tissues [1] and, it has been described as a weak plant pathogen of some plants including Cucumis melo [2], this species is considered a saprotrophic fungus
We report on the application of combined molecular (ITS and b-tubulin gene sequence analysis, PCR-RFLP and AFLP techniques), morphometric, physiological and genetic compatibility approaches to study E. nigrum variability
Summary
Ex Schlecht.) is an anamorphic ascomycete worldwide distributed which colonizes different types of soils and hosts plants. Similar to other ubiquitous mould genera, this fungus can display an endophytic lifestyle and is commonly isolated from the inner tissues of several plant species [3,4] including sugarcane [5,6], one of the most important crops in Brazil because of biofuel production (http://english.unica.com.br). Ex Schlecht) is a saprophytic ascomycete distributed worldwide which colonizes a myriad of substrates. This fungus has been known as a biological control agent for plant pathogens and produces a variety of secondary metabolites with important biological activities as well as biotechnological application. Since different isolates identified as E. nigrum have been evaluated as biological control agents and used for biocompound production, it is highly desirable that this species name refers to only one lineage. According to morphological and genetic variation, E. nigrum present two genotypes that may comprise more than one species
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