Cytogenetics Characterization of Conyza Bonariensis (L.) Cronquist Populations From Brazil)

Abstract

ResumoA espécie Conyza bonariensis (L.) Cronquist, conhecida por buva, pertence à família Asteraceae e é originária da América do Sul. Apresenta ciclo de desenvolvimento anual e é prolífica, podendo produzir até 200.000 sementes por planta, estabelece-se em diversas condições climáticas, apresenta boa adaptabilidade, sendo, geralmente, considerada planta daninha, mas também usada como medicinal. Para auxiliar na identificação precisa dessa espécie, este trabalho teve como objetivo realizar a caracterização citogenética, partindo de sementes coletadas em populações ocorrentes na região do planalto médio do Rio Grande do Sul. Para determinação do número de cromossomos, as sementes foram colocadas para germinar em placas de Petri com papel filtro duplo no germinador a 20 o C. As radículas com 2 a 5 mm de comprimento foram coletadas e submetidas ao pré-tratamento a frio (4 o C) por 18h, fixação em etanol: ácido acético (3:1) por 24h a temperatura ambiente e conservação em álcool 70% sob refrigeração até o uso. Para o preparo das lâminas, as radículas foram hidrolisadas em HCl 2N por 5 min, lavadas em água destilada e coradas com orceína acética (2%) pela técnica de esmagamento. As lâminas foram analisadas em microscópio ótico com auxí-lio da objetiva de 40x e 100x. Os resultados obtidos para as populações oriundas [39][40][41][42][43][44][45][46][47][48] 2012 40 de diferentes locais do RS foram 2n=4x=36 cromossomos para as populações de Júlio de Castilhos, Tupanciretã, Cruz Alta, Victor Graeff; e 2n= 5x= 45 para a população de Não-Me-Toque, correspondendo morfologicamente a Conyza bonariensis var. microcephala (Cabrera) Cabrera, com exceção da população de Tupanciretã, a qual se trata de Conyza bonariensis var. bonariensis. Palavras-chave: Asteraceae, buva, número de cromossomos, planta daninha. AbstractThe species Conyza bonariensis, known as hairy fleabane, belongs to the Asteraceae family and has its origin in South America. It has an annual cycle of life, being prolific and able to produce up to 200,000 seeds per plant. It occurs in various climatic conditions, showing good adaptability, and is generally considered weed, but also used as medicinal. To help on the identification of this species, the study aimed to perform cytogenetic characterization, starting from seeds collected of populations occurring in the higmedium plains region of Rio Grande do Sul. To determinate the number of chromosomes, the seeds were germinated and the root-tips with 2-5 mm in 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 under refrigeration. For the preparation of slides, the root-tips were hydrolyzed in 2N HCl for 5 min and stained with acetic orcein (2%) by the squashing technique. The results were 2n = 36 chromosomes to populations of Julio de Castilhos, Tupanciretã, Cruz Alta, Victor Graeff; and 2n = 5x = 45 for the population of Nao-Me-Toque, morphologically corresponding to Conyza bonariensis var. microcephala, except the populatio...

Molecular Characterization of Hairy Fleabane Using Rapd

“…Studies with the intention to identify glyphosate resistant Conyza species in Rio Grande do Sul also verified the occurrence of Conyza bonariensis, bonariensis and microcephala varieties (Guareschi et al, 2012). These authors, analyzing the cytogenetic characterization of the populations, verified the occurrence of tetraploid and pentaploid species.…”

“…(Schneider and Irgang, 2005;Santos et al, 2014). Guareschi et al (2012) verified the presence of the microcephala varieties of (Ritter and Baptista, 2005).…”

Technique to Obtain Mitotic Chromosomes of <i>Conyza bonariensis</i> L. Cronquist (Asteraceae)

“…The use of 8-hydroxyquinoline as an antimitotic agent has been reported for Conyza species, usually at concentrations close to 0.002 M and incubation times ranging from 2 to 24 h [5] [16] [33]. In addition, there are reports of the use of 0.005% colchicine for 2 h [34] and cold water at 4˚C for 18 h [20].…”

“…Researchers that have used acid hydrolysis with HCl 1 N at 60˚C for 10 min and HCl 2 N for 5 min, respectively, in Conyza; however, they do not mention the incubation temperature used in the process [16] [20].…”

“…A protocol that could enhance cytogenetical observations of Conyza plants is necessary because, in addition to chromosome size and number, polyploid sets have been reported for some species. Tetraploidy, 2n = 4x = 36 [17]- [20], pentaploidy, 2n = 5x = 45 [20], and hexaploidy, 2n = 6x = 54 [5] [11]- [16] [21]- [23] have previously been reported for C. bonariensis. In the mentioned studies above, only one [20] has reported the karyotype of C. bonariensis, whereas solely two [18] [16] have reported its cariogram and/or idiogram.…”