How well do ITS rDNA sequences differentiate species of true morels (Morchella)?

Abstract

Arguably more mycophiles hunt true morels (Morchella) during their brief fruiting season each spring in the northern hemisphere than any other wild edible fungus. Concerns about overharvesting by individual collectors and commercial enterprises make it essential that science-based management practices and conservation policies are developed to ensure the sustainability of commercial harvests and to protect and preserve morel species diversity. Therefore, the primary objectives of the present study were to: (i) investigate the utility of the ITS rDNA locus for identifying Morchella species, using phylogenetic species previously inferred from multilocus DNA sequence data as a reference; and (ii) clarify insufficiently identified sequences and determine whether the named sequences in GenBank were identified correctly. To this end, we generated 553 Morchella ITS rDNA sequences and downloaded 312 additional ones generated by other researchers from GenBank using emerencia and analyzed them phylogenetically. Three major findings emerged: (i) ITS rDNA sequences were useful in identifying 48/62 (77.4%) of the known phylospecies; however, they failed to identify 12 of the 22 species within the species-rich Elata Subclade and two closely related species in the Esculenta Clade; (ii) at least 66% of the named Morchella sequences in GenBank are misidentified; and (iii) ITS rDNA sequences of up to six putatively novel Morchella species were represented in GenBank. Recognizing the need for a dedicated Web-accessible reference database to facilitate the rapid identification of known and novel species, we constructed Morchella MLST (http://www.cbs.knaw.nl/morchella/), which can be queried with ITS rDNA sequences and those of the four other genes used in our prior multilocus molecular systematic studies of this charismatic genus.

A review on research advances, issues, and perspectives of morels

“…Sequences generated in recent studies (Taşkın et al 2010, 2012; O’Donnell et al 2011; Du et al 2012a, 2012b) have been recorded in this site. The scientific community not only can freely download these sequences and access information for voucher specimens and/or cultures from this website, but also can contribute their validated sequences and information to the site.…”

“…Du et al (2012b) observed that the ITS- ef1-a-rpb1-rpb2 combined-gene data could successfully identify all the phylospecies in Morchella , with the ITS gene alone identifying 77.4% of them. Unfortunately, at least two-thirds of ITS sequences of Morchella in GenBank were found to be misidentified, a problem noted for other groups of fungi (Vilgalys 2003; Ryberg et al 2008).…”

“…To minimize potential problems created by poorly annotated sequences in GenBank, and accurately identify known and novel species, the Morchella MLST database (multilocus sequence typing, http://www.cbs.knaw.nl/ Morchella /) was constructed (Du et al 2012b). Sequences generated in recent studies (Taşkın et al 2010, 2012; O’Donnell et al 2011; Du et al 2012a, 2012b) have been recorded in this site.…”

“…In this section, the results reported in Taşkın et al (2010, 2012), O’Donnell et al (2011), Du et al (2012a, 2012b), Voitk et al (2014), Elliott et al (2014), Pildain et al (2014), Beug and O’Donnell (2014) and Richard et al (2014) have been integrated to provide a comprehensive picture of the species distribution and ecological diversity of Morchella .…”

Two species of true morels (the genus Morchella, Ascomycota) recorded in the Ojców National Park (south Poland)

“…The uncertainty described above is an example of problems arising from attempts to accommodate morphologically defined species names to molecularly defined monophyletic groups. The inaccuracy in using of morphologically defined binomial species names to describe genetic diversity detected with molecular methods resulted in adoption of provisional system of species designations (see [7,24,[33][34][35][36]), where M. deliciosa is referred to as Mel-26 and M. esculenta as Mes-8. According to the newest data provided by Richard et al [12], the name Morchella conica is illegitimate at the species rank, while the Morchella elata status needs further study to be definitively resolved.…”