New cytotaxonomical determinants recognized in six taxa of Agave in the sections Rigidae and Sisalanae

Abstract

New cytotaxonomical determinants are presented for the following taxa of Agave: (I) section Rigidae: Agave fourcroydes Lemaire (5x = 150), first karyotype; Agave angustifolia Haworth (sensu Gentry), new count (6x = 180), first karyotype; Agave angustifolia Haworth var. marginata Hort. (2x = 60); and Agave tequilana Weber, new count (2x = 60), first karyotype; (II) section Sisalanae: Agave sisalana Perrine (5x = 150), first karyotype; and (III) intersectional hybrid: Agave hybrid 11 648 new count (2x = 60), first karyotype. Chromosomes are classified and arm number, chromatin length, and variability are discussed. These results suggest (i) a speciation process via limited rearrangements and point mutations in the small chromosomes of the complement, within the euploidy level rather than karyotype diversification and (ii) a reconsideration to assign them to the 2C level of Stebbins karyotype classification. Key words: fiber agaves, karyotype analysis.