Phylogenetic relationships in genus Arachis based on ITS and 5.8S rDNA sequences

Abstract

BackgroundThe genus Arachis comprises 80 species and it is subdivided into nine taxonomic sections (Arachis, Caulorrhizae, Erectoides, Extranervosae, Heteranthae, Procumbentes, Rhizomatosae, Trierectoides, and Triseminatae). This genus is naturally confined to South America and most of its species are native to Brazil. In order to provide a better understanding of the evolution of the genus, we reconstructed the phylogeny of 45 species using the variation observed on nucleotide sequences in internal transcribed spacer regions (ITS1 and ITS2) and 5.8 S of nuclear ribosomal DNA.ResultsIntraspecific variation was detected, but in general it was not enough to place accessions of the same species in different clades. Our data support the view that Arachis is a monophyletic group and suggested Heteranthae as the most primitive section of genus Arachis. The results confirmed the circumscriptions of some sections (Caulorrhizae, Extranervosae), but raised questions about others. Sections Erectoides, Trierectoides and Procumbentes were not well defined, while sections Arachis and Rhizomatosae seem to include species that could be moved to different sections. The division of section Arachis into A and B genome species was also observed in the phylogenetic tree and these two groups of species may not have a monophyletic origin. The 2n = 2x = 18 species of section Arachis (A. praecox, A. palustris and A. decora) were all placed in the same clade, indicating they are closely related to each other, and their genomes are more related to B genome than to the A genome. Data also allowed insights on the origin of tetraploid A. glabrata, suggesting rhizome appeared twice within the genus and raising questions about the placement of that species in section Rhizomatosae.ConclusionThe main clades established in this study in general agreed with many other studies that have used other types of evidences and sets of species, being some of them included in our study and some not. Thus, the relationships established can be a useful framework for future systematic reviews of genus Arachis and for the selection of species to pre-breeding programs.

New hybrids from peanut (Arachis hypogaea L.) and synthetic amphidiploid crosses show promise in increasing pest and disease tolerance

“…& W.C. Gregory (Robledo and Seijo, 2010). This new classification is supported by systematic molecular studies on the genus Arachis (Bechara et al, 2010;Friend et al, 2010;Wang et al, 2010).…”

“…A. batizocoi was for many years considered a B genome, but was recently re-classified as a K genome species (Robledo and Seijo, 2010). Based on phylogenetic data, A. batizocoi is more distantly related to A. hypogaea than A. magna, while A. cardenasii and A. helodes, both A genome species, form a monophyletic group (Bechara et al, 2010). Therefore, we expected to observe more polymorphisms between IAC 503 and Di 07T than between IAC 503 and An 8.…”

Research Article Coupled transcript and metabolite identification: insights on induction and synthesis of resveratrol in peanut, wild relatives and synthetic allotetraploid.

“…Section Arachis is one of the nine taxonomic sections of genus Arachis and it comprises 31 species (Krapovickas and Gregory, 2007;Valls et al, 2013) that are phylogenetically very close to peanut (Bechara et al, 2010). Section Arachis species are found in different environments and because of that they may harbor resistant genes related to abiotic and biotic stress that are not found in cultivated peanut (Pande and Rao, 2001).…”

Research Article Morphological, cytogenetic, and molecular characterization of Arachis kuhlmannii Krapov. & W.C. Greg. (Leguminosae).

“…Thus, we believe that accessions in groups 1 and 2 may belong to the same species. Bechara et al (2010) using ITS and 5.8S markers also noted the similarity among accessions of A. kuhlmannii and accessions of A. simpsonii and A. helodes. Group 2 included accessions collected in the region of Cáceres and Cuiabá identified as members of the species A. kuhlmannii, A.…”