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

Guillermo Seijo,José Francisco Montenegro Valls,Adriana Regina Custódio

doi:10.1590/s1415-47572013000300011

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.

Highlights

Arachis L. is a South American legume genus found in Argentina, Bolivia, Brazil, Paraguay and Uruguay
Twelve Brazilian accessions of five Arachis species maintained in the Wild Arachis Genebank at Embrapa Genetic Resources and Biotechnology in Brasília, Brazil, were analyzed (Table 1)
Two large distal 5S rDNA loci were detected in the long arms of one submetacentric pair of chromosomes

Summary

Introduction

Arachis L. is a South American legume genus found in Argentina, Bolivia, Brazil, Paraguay and Uruguay. This genus consists of 80 species arranged in nine taxonomic sections (Krapovickas and Gregory, 1994; Lavia et al, 2009; Valls and Simpson, 2005). Section Arachis is the most numerous (33 species) and important since it contains the cultivated peanut, A. hypogaea L., and its closest wild relatives (Moretzsohn et al, 2013). = 40) have been reported for species included in the section Arachis (Fernández and Krapovickas, 1994; Lavia, 1996, 1998, 2000; Lavia et al, 2008; Peñaloza and Valls, 2005).

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Conclusion