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Fig. 3 | IMA Fungus

Fig. 3

From: Unambiguous identification of fungi: where do we stand and how accurate and precise is fungal DNA barcoding?

Fig. 3

Comparison of BLAST-based (pairwise alignment) vs. tree-based (multiple alignment) identification of a target fungal ITS sequence (DB42771, Vietnam; see Lücking et al. 2020). BLAST (both blastn and megablast) initially suggested Trametes cubensis or Leiotrametes lactinea to be the most likely identification: the label ‘cf. cubensis’ had the three highest named BLAST hits and appeared six times among the top ten named hits. Yet, multiple alignment-based phylogenetic analysis placed the target sequence in a clade corresponding to T. menziesii, described from Indonesia. Apart from demonstrating the shortcomings of BLAST identifications, this example illustrates numerous problems with reference sequence labeling, including wrongly identified sequences and confusion about species and even genus concepts and nomenclature (Lücking et al. 2020). A user not aware of such issues would not be able to obtain a reliable identification using BLAST only, whereas the alignment-based phylogenetic approach followed by a verification process provided an accurate result in this case. Notably, two remedies would substantially improve BLAST identification results: (1) correct labeling of the reference sequences through third-party annotations (middle column), plus (2) sorting BLAST results by percentage identity (highlighted values)

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