| Sumari: | Background and Aims: Flaveria is an American genus with 23 species; in Argentina it is represented by two of them both native and annual: F. bidentis (which is cited as a weed of agroecosystems) and F. haumanii. The genus is mentioned with a base chromosome number of x=18 and cytogenetic backgrounds for F. bidentis are know, but not so for F. haumanii. The aim of this work was to cytogenetically characterize F. bidentis and F. haumanii through the analysis of mitosis, meiotic behavior and estimation of pollen grain viability.
Methods: The material was collected in the province of Santiago del Estero (Argentina). The root tips were pretreated with 8-hydroxyquinoline 0.002 M for eight hours. Inflorescences and root tips were fixed in Farmer and preserved in cold 70% ethyl alcohol. To stain chromosomes 2% propionic hematoxylin was used. The viability of pollen grains was estimated with the Mützing and DAF stain solutions.
Key results: Flaveria bidentis and F. haumanii have a sporophytic chromosome number of 2n=36, with a symmetric unimodal karyotype. The meiotic behavior was regular, in diakinesis n=18 bivalent was observed and the estimated viability of the pollen grains was greater than 90%.
Conclusions: The sporophytic and gametophytic chromosomal numbers of F. haumanii are mentioned for the first time; in addition, through meiotic analysis the cytogenetic information is completed for F. bidentis. These are the first data related to pollen grain viability.
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