Characterization of Brazilian accessions of wild Arachis species of section Arachis (Fabaceae) using heterochromatin detection and fluorescence in situ hybridization (FISH)

Abstract

The cytogenetic characterization of Arachis species is useful for assessing the genomes present in this genus, for establishing the relationship among their representatives and for understanding the variability in the available germplasm. In this study, we used fluorescence in situ hybridization (FISH) to examine the distribution patterns of heterochromatin and rDNA genes in 12 Brazilian accessions of five species of the taxonomic section Arachis. The heterochromatic pattern varied considerably among the species: complements with centromeric bands in all of the chromosomes (A. hoehnei) and complements completely devoid of heterochromatin (A. gregoryi, A. magna) were observed. The number of 45S rDNA loci ranged from two (A. gregoryi) to eight (A. glandulifera), while the number of 5S rDNA loci was more conserved and varied from two (in most species) to four (A. hoehnei). In some species one pair of 5S rDNA loci was observed adjacent to 45S rDNA loci. The chromosomal markers revealed polymorphism in the three species with more than one accession (A. gregoryi, A. magna and A. valida) that were tested. The previous genome assignment for each of the species studied was confirmed, except for A. hoehnei. The intraspecific variability observed here suggests that an exhaustive cytogenetic and taxonomic analysis is still needed for some Arachis species.

Crossability of Arachis valida and B genome Arachis species

“…By analysis of morphological characteristics and the low pollen viability estimates for the hybrids were confirmed. These data support the theory that the higher pollen viability indicates a higher probability for affinities between species and accessions (Fernández and Krapovickas, 1994;Custodio et al, 2013). The accession V 13514 of A. valida used in this study has high resistance to early and late leaf spot (Fávero et al, 2009), which are economically, important diseases in Brazil (Santos et al, 2013).…”

“…These species are cytologically similar to A. ipaënsis because their chromosomes do not have heterochromatic bands . By cytogenetic and molecular analyses and crosses, A. valida has been found to be close to A. ipaënsis (Custodio, 2009;Custodio et al, 2013;Moretzsohn et al, 2013). A. valida has a higher number of accessions compared to the only one available accession of A. ipaënsis, needed to expand the genetic basis for the B genome in peanut-breeding programs.…”

Organography of greenhouse and field accessions of wild Arachisspecies (section Arachis)

“…Similarly, A. ipaënsis was close to A. valida. This result supports molecular marker studies that show that A. valida is close to A. ipaënsis and has B genome (Robledo and Seijo, 2010;Custodio et al 2013).…”

Brazilian Kayabi Indian accessions of peanut, Arachis hypogaea (Fabales, Fabaceae): origin, diversity and evolution

“…The 45S rDNA loci in the three Xingu accessions were similar to the sum of those present in A. duranensis (A2, A10) and A. ipaënsis (B3, B7 and B10), distinctive from those in A. stenosperma (A2, A10 and A7) (Robledo et al, 2009) and A. magna (B3, B7, B10 and B4) (Robledo and Seijo, 2010). Interestingly, the cytogenetic analysis of five Brazilian accessions of A. magna (V 13748, V 13765, V 14724, V 14727 and V 14750) (Custódio et al, 2013) identified polymorphisms of the 45S rDNA loci among themselves, and these various patterns also differed from the K 30097. Most importantly is that all of the patterns observed in these accessions were different from that in the Xingu accessions and conclusively, it is assumed that none of these accessions may had participate in the genome origin of the Xingu accessions.…”