Karyotype studies in cultivars of Agave tequilana Weber

Abstract

Abstract Agave tequilana cultivars “Lineño”, “Azul Listado”, “Moraleño”, “Azul”, “Sigüin”and “Pata de Mula” were diploids with 2n=2x=60; cult. “Bermejo” were triploid with 2n=3x=90, and cult. “Chato” tetraploid with 2n=4x=120 (x= 30). A. tequilana cultivars show a bimodal karyotype consisting of 10 large + 50 small chromosomes in diploids; 15 large + 75 small chromosomes in triploids and 20 large + 100 small chromosomes in tetraploids. In diploids they had secondary constriction in one pair of large chromosome and in the third or fourth largest homologous chromosome groups in triploids and tetraploids, respectively. The variation among cultivars was clearly evident in the arm ratio, proportion of different types of large and small chromosomes, mean of genome length and asymmetry index of karyotypes. The variation observed among Agave tequilana cultivars is possible due to rearrangements in the large and small chromosomes of the complement. These results support the separation of diploid cultivars “Azul”, “Azul Listado”, “Moraleño” and “Sigüin” from diploid “Pata de Mula” and polyploids “Bermejo” (3x) and “Chato” (4x).