CYTOGENETICS CHARACTERIZATION OF CONYZA BONARIENSIS (L.) CRONQUIST POPULATIONS FROM BRAZIL

The species Conyza bonariensis, known as hairy fleabane, belongs to the Asteraceaefamily and has its origin in South America. It has an annual cycleof life, being prolific and able to produce up to 200,000 seeds per plant.It occurs in various climatic conditions, showing good adaptability, and isgenerally considered weed, but also used as medicinal. To help on the identificationof this species, the study aimed to perform cytogenetic characterization,starting from seeds collected of populations occurring in the higmediumplains region of Rio Grande do Sul. To determinate the numberof chromosomes, the seeds were germinated and the root-tips with 2-5 mmin length were collected and subjected to cold pretreatment (4°C) for 18h,fixed in ethanol: acetic acid (3:1) for 24h and kept in 70% ethanol underrefrigeration. For the preparation of slides, the root-tips were hydrolyzedin 2N HCl for 5 min and stained with acetic orcein (2%) by the squashingtechnique. The results were 2n = 36 chromosomes to populations of Juliode Castilhos, Tupancireta, Cruz Alta, Victor Graeff; and 2n = 5x = 45 for thepopulation of Nao-Me-Toque, morphologically corresponding to Conyza bonariensisvar. microcephala, except the population of Tupancireta, which it isConyza bonariensis var. bonariensis.