Abstract
Oyster mushrooms (genus Pleurotus) are widespread and comprise the most commonly cultivated edible mushrooms in the world. Species identification of oyster mushroom spawn based on cultural, morphological, and cultivated characteristics is time consuming and can be extraordinarily difficult, which has impeded mushroom breeding and caused economic loss for mushroom growers. To explore a precise and concise approach for species identification, the nuclear ribosomal internal transcribed spacer (ITS), 28S rDNA, and the widely used protein-coding marker translation elongation factor 1α (EF-1α) gene were evaluated as candidate DNA barcode markers to investigate their feasibility in identifying 13 oyster mushroom species. A total of 160 sequences of the candidate loci were analyzed. Intra- and interspecific divergences and the ease of nucleotide sequence acquisition were the criteria used to evaluate the candidate genes. EF-1α showed the best intra- and interspecific variation among the candidate markers and discriminated 84.6% of the species tested, only being unable to distinguish two closely related species Pleurotus citrinopileatus and Pleurotus cornucopiae. Furthermore, EF-1α was more likely to be acquired than ITS or 28S rDNA, with an 84% success rate of PCR amplification and sequencing. For ITS and 28S rDNA, the intraspecific differences of several species were distinctly larger than the interspecific differences, and the species identification efficiency of the two candidate markers was worse (61.5 and 46.2%, respectively). In addition, these markers had some sequencing problems, with 55 and 76% success rates of sequencing, respectively. Hence, we propose EF-1α as a possible DNA barcode marker for oyster mushroom spawn.
Highlights
The pleurotoid fungi (Pleurotaceae, Agaricales, Basidiomycota), commonly known as oyster mushrooms, are widespread and comprise the most commonly cultivated edible mushrooms in the world
The intra- and interspecific sequence variations of the candidate DNA barcode regions for each of the 13 species of Pleurotus mushroom spawn are shown visually in Figure 1, with the analyzed data in Supplementary Table 2. This result indicates that the elongation factor 1α (EF-1α) gene provided the best intra- and interspecific variation and the most species resolution power compared with the other markers (Figure 1)
The intra- and interspecific variations of internal transcribed spacer (ITS) and 28S rDNA in the investigated oyster mushroom spawn were not appropriate because the intraspecific differences of several species were distinctly larger than the interspecific differences for both regions, which may lead to misidentification
Summary
The pleurotoid fungi (Pleurotaceae, Agaricales, Basidiomycota), commonly known as oyster mushrooms, are widespread and comprise the most commonly cultivated edible mushrooms in the world. In the majority of cases, due to the similarity of morphological traits, phenotypic plasticity under different cultivation substrates and environmental conditions, sometimes ambiguous and inconclusive mating tests (Bresinsky et al, 1976; Sánchez, 2004; Avin et al, 2012; Shnyreva and Shnyreva, 2015), and the lack of differential hyphal and mycelial characteristics, species identification of oyster mushroom spawn is time consuming and extraordinarily difficult, which has been an obstacle to mushroom breeding and caused economic loss for mushroom growers (Li et al, 2017) To address this issue, diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and molecular biology techniques have been employed (Yang et al, 2007; Huerta et al, 2010; Pawlik et al, 2012; Zervakis et al, 2012), but these techniques require much effort and can be inefficient. Selecting an appropriate DNA barcode marker for the reliable and efficient species identification of oyster mushroom spawn is essential
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