Karyotypic studies in wild germplasm of arachis

Genet Resour Crop Evol (2009) 56:755–764 DOI 10.1007/s10722-008-9399-6

RESEARCH ARTICLE

Karyotypic studies in wild germplasm of Arachis (Leguminosae)
Graciela I. Lavia Æ Alejandra M. Ortiz Æ ´ Aveliano Fernandez

Received: 8 July 2008 / Accepted: 1 December 2008 / Published online: 30 December 2008 Ó Springer Science+Business Media B.V. 2008

Abstract The karyomorphology for eightdiploid species of Arachis belonging to three sections has been described for the first time, Sect. Extranervosae: A. macedoi (2n = 20m) and A. retusa (2n = 14m ? 6sm); Sect. Heteranthae: A. sylvestris (2n = 16m ? 4sm); Sect. Procumbentes: A. chiquitana (2n = 18m ? 2sm); Sect. Arachis: A. cruziana (2n = 18m ? 2sm), A. herzogii (2n = 18m ? 2sm), A. simpsonii (2n = 20m) and A. williamsii (2n = 20m). Apair of satellited chromosomes was observed in all species. A chromosomes were found in A. chiquitana, A. herzogii and A. simpsonii. Karyotypic differences between sections were observed, but not enough to establish a characteristic karyotype pattern for each
´ G. I. Lavia Á A. Fernandez ´ Miembros de la Carrera del Investigador Cientıfico ´ (CONICET), Instituto de Botanica del Nordeste, C.C. 209,3400 Corrientes, Argentina G. I. Lavia (&) Facultad de Ciencias Agrarias (UNNE), Instituto ´ de Botanica del Nordeste, C.C. 209, 3400 Corrientes, Argentina e-mail: lavia@agr.unne.edu.ar A. M. Ortiz ´ Becaria de CONICET, Instituto de Botanica del Nordeste, C.C. 209, 3400 Corrientes, Argentina ´ A. Fernandez Facultad de Ciencias Exactas y Naturales y Agrimensura ´ (UNNE), Instituto de Botanica delNordeste, C.C. 209, 3400 Corrientes, Argentina

section. However, the species may be differentiated by the presence of A chromosomes, the type and position of satellites, and the karyotype formulae. These results are discussed with regard to karyotype evolution in Arachis to contribute to understanding the role of chromosome changes in the evolution of the genus. Keywords Arachis Á Chromosomes ÁKaryotype evolution Á Wild peanut

Introduction Arachis (Leguminosae) is an indigenous and economically important genus of South America. It comprises 80 annual and perennial species (Krapovickas and Gregory 1994; Valls and Simpson 2005), classified into nine sections based on morphological and chromosomal features, cross compatibility and hybrid fertility (Krapovickas and Gregory 1994). Peanut(A. hypogaea L.) is one of the most important sources of dietary protein in the world. However, considering their productivity, this crop remains underexploited because of its susceptibility to pests and diseases. The major constraint to the genetic improvement of peanut is the narrow genetic base of the extant crop. Wild Arachis species, by contrast, are diverse and have the genetic variability andagronomically useful characters needed to improve the peanut (Holbrook and Stalker 2003) and constitute valuable

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resources for the genetic upgrading of peanut. In this sense, information on the cytogenetics and phylogenetic relationships among wild species and between these species and the peanut is critical to the rational developmentof breeding programs and complete utilization of the wild materials. Chromosomal data have played a pivotal role in accelerating crop improvement (Jauhar 2006) and our comprehension of the phylogenetic relationships between wild and cultivated species (Cao 2003). On the other hand, cytogenetic studies are also relevant in the study of plant evolution and diversification (Stebbins 1971). Moreover,the analysis of karyotype characteristics has contributed valuable data for inferring evolutionary trends within particular plant groups and analyzing traits such as changes in chromosome numbers (Mercado-Ruaro and Delgado-Salinas 1998), in karyotype symmetry, and in chromosome length (Poggio et al. 2007). Karyotype analysis in Arachis began with studies by Husted (1933), who described the SAT...