Studies On Phylogenetic Relationships Of Pleurotus Based On Nuclear Large Subunit Ribosomal DNA And Its Sequences

As the food and pharmaceutical macro fungi,Pleurotus has an important economic value,which is closely related with the human.Pleurotus species are so many that the origin and evolution is more complex and that the classification is more confusion, Pleurotus phylogenetic relations have been in dispute.With the rapid developing of modern biological science and technology,more and more new methods and technologies are emerging and applied to the Pleurotus phylogeny and classification research.On the base of the traditional morphologic identification,27 species of Pleurotus or subspecies of 48 strains of the large subunit ribosomal DNA(LSU rDNA) and internal transcription space(ITS) were sequenced by PCR products clone or direct sequencing.The phylogenetic tree of Pleurotus was assembled by the software MAGA and PHYLIP with Neighbour-Joining(N-J) and Maximums Parsimary(MP) method with the out-group of Hohenbuehelia serotina,Agaricus bisporus and Lentinula calories.It was expected to clarifying its phylogenetic renationship and providing reference for scientific research and production usage.According to mycelium morphological analysis,48 Pleurotus strains can be divided into five major groups:the fast group is Pleurotus dryinus;the second group includes Pleurotus australis,Pleurotus abalonus,Pleurotus cystidiosus,Pleurotus cystidiosus var. formosensis and Pleurotus smithii;The third group includes Pleurotus djamor and Pleurotus salmoneostramineus;the fourth group is Pleurotus lampas;the fifth group includes all other strains tested.According to the result of fruit body morphology observed of Pleurotus,the tested strains can be identified into species except Pleurotus abieticola,Pleurotus euosmus,Pleurotus incarnates,Pleurotus lampas,Pleurotus rattenburyi,Pleurotus columbinus and Pleurotus tuberregium which were not fruiting so that the fruit body can not be observed.Based on LSU rDNA sequence analysis,the phylogenetic tree of Pleurotus was assembled and showed that Pleurotus strains were divided into six main branches.The first branch includes Pleurotus rattenburyi alone;the second branch includes Pleurotus djamor,Pleurotus salmoneostramineus,Pleurotus flabellatus,Pleurotus calyptratus, Pleurotus citrinopileatus and Pleurotus euosmus;the third branch includes Pleurotus dryinus and Pleurotus tuberregium;the forth branch is Coremiopleurotus group, including Pleurotus abalonus,Pleurotus smithii,Pleurotus cystidiosus and its variants; the fifth branch is only Pleurotus australis;the sixth branch includes Pleurotus eryngii complex,Pleurotus ostreatus complex,Pleurotus pulmonarius and Pleurotus abieticola. Pleurotus ostreatus complex includes Pleurotus ostreatus,Pleurotus spodoleuces, Pleurotus columbinus,Pleurotus sapidus and Pleurotus floridanus.Phylogenetic tree also showed that Coremiopleurotus group,including Pleurotus australis,Pleurotus abalomus, Pleurotus cystidiosus,Pleurotus smithii,may be polyphyletic.Based on ITS sequence analysis,the phylogenetic tree of Pleurotus was assembled and showed that it gradually extended to six main branches from the roots of the tree, representing the six major groups of Pleurotus.Branchâ… is Pleurotus rattenburyi and Hohenbuehelia serotina;Branchâ…¡is only Pleurotus tuberregium;Branchâ…¢includes Pleurotus dryinus,Pleurotus citrinopileatus and Pleurotus euosmus;Branchâ…£is Pleurotus australis,Pleurotus abalonus,Pleurotus smithii,Pleurotus cystidiosus and its variants;Branchâ…¤includes Pleurotus djamor,Pleurotus salmoneostramineus,Pleurotus flabellatus,Pleurotus incarnates and Pleurotus calyptratus;Branchâ…¥includes Pleurotus pulmonarius,Pleurotus arbieticola,Pleurotus eryngii,Pleurotus nebrodensis,Pleurotus ostreatus,Pleurotus floridanus,Pleurotus columbinus,Pleurotus spodoleucus,Pleurotus conucopiae and Pleurotus sapidus.In these groups,different strains of the same Pleurotus species can be together well.At theâ…¥branch,Pleurotus strains were divided into five groups evidently.Group A is Pleurotus pulmonarius;Group B is P.arbieticola; Group C is Pleurotus eryngii complex;Group D is Pleurotus nebrodensis;Group E is Pleurotus ostreatus complex.Compare with LSU sequences,ITS sequences showed prominent advantage on species identification and classification.The phylogenetic tree also showed that Coremiopleurotus group,including Pleurotus australis,Pleurotus abalomus,Pleurotus cystidiosus and Pleurotus smithii,may be monophyletic.It can be speculated that Pleurotus fuscus vat.ferulae is probably Pleurotus ferulae.The phylogenetic tree of Pleurotus was assembled respectively by the LSU and ITS sequence,they all showed that the monomitic and dimitic hyphal systems of Pleurotus were probably polyphyletic,respectively.P.calyptratus had close relationship with P. djamor,Pleurotus salmoneostramineus and Pleurotus flabellatus.Pleurotus citrinopileatus and Pleurotus conucopiae were different species.P.lampas had a far relationship with other members of the Pleurotus,Its systematic location should be re-established.Two gene trees can reflect the phylogenetic relationship belong the strains of Pleurotus exactly,and Pleurotus groups represented by the two different gene tree were basically the same,which reflected the origin and evolution relations were also the same.Compared to LSU sequences,ITS sequences have prominent advantages on the identification of different species or strains.