Nuclear genome size and cytotype analysis inAgave cupreataTrel. & Berger (Agavaceae)

Abstract

This study is a cytogenetic characterization by karyotyping and a determination of the DNA content by flow cytometry of wild populations of Agave cupreata from the Guerrero State, Mexico. Three of the studied populations were diploids (2n = 2x =60) and one population had tetraploid (2n = 4x = 120), pentaploid (2n = 5x = 150) and hexaploid (2n = 6x = 180) plants. Diploid populations had three different structural cytotypes. One population showed polyploid cytotypes. A. cupreata showed a bimodal karyotype of 10 large + 50 small chromosomes in diploids; 20 large + 100 small chromosomes in tetraploids and 25 large + 125 small chromosomes in pentaploids. In diploids, they had secondary constriction in one pair of the large chromosomes and, in the fourth or fifth large homologous chromosome groups, in polyploid plants. The arm ratio, the proportion of different types of large and small chromosomes, the mean of genome length and the asymmetry index of karyotypes clearly varied among diploid and polyploid cytotyp...