A Combination of the "Squash" and "Splash" Techniques to Obtain the Karyotype and Assess Meiotic Behavior of Prosopis laevigata L. (Fabaceae: Mimosoideae).

Abstract

A combination of modified squash and splash techniques was used for a cytogenetic study of mitotic and meiotic cells of Prosopis laevigata. The mitotic karyotype was obtained for the species, and meiotic behavior was monitored from prophase I through the synaptonemal complex (SC). Analysis using light microscopy showed 2n=28, with chromosomes that, depending on the technique employed, varied in length from 0.84 to 1.84 μm in squashed specimens and from 1.0 to 1.82 μm in splashed specimens. These values are larger than those previously recorded for other South American species of the genus. The karyotype was studied by the splash method. The frequency of tetraploid cells was about 11% of 2052 metaphase cells examined. Meiosis was normal, because 14 bivalents were seen at metaphase I. The SC in pachytene showed regular features and an asynchronous pairing pattern with some short segments of lateral elements apically or interstitially unpaired, and occasional partner exchanges between three lateral elements. A constant association of the telomeric end of a bivalent with the nucleolus in mid-and late-prophase suggests the location of an active nucleolus organizer region (NOR) and its relation with a unique pair of mitotic chromosomes with satellites. The techniques employed here are recommended for species not amenable to cytogenetic studies with conventional techniques.