Karyotype and DNA Content Patterns of the Genus Arachis in a Phylogenetic Context

SILVESTRI MARÍA CELESTE; ORTIZ, ALEJANDRA MARCELA; ROBLEDO, GERMÁN; SAMOLUK SEBASTÍAN; SEIJO, GUILLERMO; LAVIA, GRACIELA INÉS

Foz de Iguazú

Conferencia; 21st International Chromosome Conference (ICC); 2016

International Chromosome and Genome Society

Arachis is a South American genus that includes 82 autogamousand geocarpic species. Most species are diploids with x = 10,4 are diploids with x = 9, and 5 are tetraploids with x = 10. Basedon morphology and cross-compatibility, these species were arrangedin 9 sections and different genomes. Classical and molecularcytogenetics revealed large karyotype variability among speciesand has also been very important for the infrageneric arrangementof the genus. The objective of this research was to make inferencesabout the direction of changes in different chromosome markersand DNA content during the evolution of the genus. For this purpose,new cytogenetic (FISH with 45S and 5S rDNA and heterochromaticmarkers) and DNA content (flow cytometry estimated2C values) data, together with those available, were analyzed in aphylogenetic context based on (available and new data) ITS sequences.This analysis revealed that in the evolutionary history ofthe genus: (1) there is a general tendency of a genome size (Cx)increase, although independent reductions occurred more thanonce, (2) reduction of the basic chromosome number (from x = 10to x = 9) occurred twice, (3) polyploidization based on x = 10 occurredmore than once, (4) ?A chromosomes? originated only once,(5) different patterns of DAPI/CMA heterochromatic bands wereobserved in 2 (out of 3) of the main clades, and (6) the number of5S rDNA loci is generally 1 pair (exceptions are found in differentclades), while the number of 45S rDNA is more variable (1?5pairs). Most of the chromosome characters analyzed according tothe ITS phylogenetic hypothesis for genus Arachis did not show aunidirectional evolutionary history.