Taxonomic relationships amongArachissect.Arachisspecies as revealed by AFLP markers

Abstract

Cultivated peanut, Arachis hypogaea L., is a tetraploid (2n = 4x = 40) species thought to be of allopolyploid origin. Its closest relatives are the diploid (2n = 2x = 20) annual and perennial species included with it in Arachis sect. Arachis. Species in section Arachis represent an important source of novel alleles for improvement of cultivated peanut. A better understanding of the level of speciation and taxonomic relationships between taxa within section Arachis is a prerequisite to the effective use of this secondary gene pool in peanut breeding programs. The AFLP technique was used to determine intra- and interspecific relationships among and within 108 accessions of 26 species of this section. A total of 1328 fragments were generated with 8 primer combinations. From those, 239 bands ranging in size from 65 to 760 bp were scored as binary data. Genetic distances among accessions ranged from 0 to 0.50. Average distances among diploid species (0.30) were much higher than that detected between tetraploid species (0.05). Cluster analysis using different methods and principal component analysis were performed. The resulting grouping of accessions and species supports previous taxonomic classifications and genome designations. Based on genetic distances and cluster analysis, A-genome accessions KG 30029 (Arachis helodes) and KSSc 36009 (Arachis simpsonii) and B-genome accession KGBSPSc 30076 (A. ipaensis) were the most closely related to both Arachis hypogaea and Arachis monticola. This finding suggests their involvement in the evolution of the tetraploid peanut species.

Cloning and polymorphism analysis of the 2-methyl-6-phytyl-1,4-benzoquinol methyltransferase gene (VTE3) in Arachis hypogaea, A. duranensis, and A. ipaënsis

“…The 0.1% difference can be accounted for by subtle differences in the intron repeat sequence between the various samples. Different molecular markers were used by Raina et al (2001) and Milla et al (2005), confirming the conclusions that the genetic base of cultivated peanuts is narrow and that polymorphisms occur only at low levels. Different peanut VTE3 cultivars have been demonstrated to be highly homologous, with the 2 subspecies A. hypogaea ssp fastigiata and A. hypogaea ssp hypogaea being the most likely to share the same diploid wild ancestral species, although validation through further study, including larger cohorts and examination of additional molecular markers is needed to validate these results.…”

“…Studies using amplified fragment length polymorphism (Milla et al, 2005) and fluorescence in situ hybridization (Seijo et al, 2004) methods confirmed that A. hypogaea variant cultivars share the same ancestral origin, and the present study concluded that A. duranensis and A. ipaënsis are likely to be the ancestors of contemporary cultivated species. Singh (1988) synthesized amphidiploid peanuts, hybridized them with different cultivars, and studied the cell morphology and chromosome synapsis.…”

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

“…Several authors have shown A. magna to be very similar to A. ipaënsis (Krapovickas and Gregory, 1994;Milla et al, 2005;Moretzsohn et al, 2009), which is the donor of the B genome to the cultivated peanut (Kochert et al, 1996). A. batizocoi was for many years considered a B genome, but was recently re-classified as a K genome species (Robledo and Seijo, 2010).…”

The Value of Diploid Peanut Relatives for Breeding and Genomics

“…Based on rDNA loci and chromosomes with centromeric heterochromatin, Robledo et al (2009) described three karyotypic subgroups within the A genome and grouped the cultivated peanut with A. duranensis, A. villosa, A. schininii, and A. correntina. Other studies support placing A. hypogaea closely with A. duranensis (Moretzsohn et al, 2004;Milla et al, 2005a;Bravo et al, 2006;Koppolu et al, 2010;Calbrix et al, 2012). The chromosomes of B genome species are karyologically more diverse than those with an A genome (Fernandez and Krapovickas, 1994;Seijo et al, 2004).…”