Determination Of Agave Angustifolia Haw. Cytotypes By Flow Cytometry
G Palomino, J Martínez and I MéndezJardín Botánico, Instituto de Biología e Instituto de Matemáticas Aplicadas y Sistemas, Universidad Nacional Autónoma de México, D. F. 04510, México
Flow cytometric analysis of nuclear DNA content of Agave angustifolia using nuclei isolated from leaf tissue showed one population with a diploid cytotype (2n = 2x = 60) and other with a triploid one (2n = 3x = 90). Genome size in diploids was 2C = 8.477 pg, whereas in triploids it was 12.420 pg. The 1Cx value in diploids (Mbp = 4139) was significantly higher than in triploids (Mbp = 4057). Karyotypes in diploid (2n = 42m+8sm+2st+8t) and in triploid plants (2n = 60m+12sm+6st+12t) showed different proportions of chromosome types, probably caused by heterozygosis for chromosome exchange. Diploid plants had GL = 161.53 µm, a value significantly lower than in triploids (181.06 µm). GL in the monoploid chromosome set of diploids (1Cx = 80.76 µm) was higher than in that of triploids (60.35 µm), showing that the genome size of triploid plants had a lower proportion of DNA sequences than diploid ones, sequences that might have been eliminated during the polyploidization process(1). Vegetative reproduction, common in this species, has been the way of maintaining the triploid clones that have been selected by mescal beverage producers.
1. Palomino G, Dolezel J, Méndez I, Rubluo A (2003). Caryologia 56: 37-46.