Meiotic behaviour and B chromosomes in Argentine populations of Chrysolaena verbascifolia (Vernonieae: Asteraceae)

Abstract

Four populations of Chrysolaena verbascifolia (Vernonieae: Asteraceae) from localities in Argentina were cytologically analysed for meiotic behaviour and pollen viability. This is the first meiotic analysis in the species. All were diploids with 2n = 2x = 20 and all showed quite regular meiotic behaviour. We also report the occurrence of accessory chromosomes in all the populations of the species. The majority of the populations displayed regular bivalent formation during late prophase stages and metaphase I, and chromosome segregation at anaphase. However, some chromosomal irregularities were recorded, mainly during meiosis I, including univalents, out-of-plate chromosomes and precocious segregation in metaphase, and laggards and chromatin bridges in anaphase. The B chromosomes and abnormal behaviours of the chromosomes during meiosis observed did not affect pollen development in these taxa, as viability was always high.