Monitoramento da embriogênese somática de Carica papaya L. por técnicas citogenéticas e de citometria de fluxo

• Ano de defesa: 2010
• Autor(a) principal: Abreu, Isabella Santiago de
• Orientador(a): Carvalho, Carlos Roberto de
• Banca de defesa: Picoli, Edgard Augusto de Toledo , Caixeta, Eveline Teixeira
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Genética e Melhoramento
• Departamento: Genética animal; Genética molecular e de microrganismos; Genética quantitativa; Genética vegetal; Me
• País: BR
• Palavras-chave em Português: Carica papaya; Embriogênese somática; Mamão; Citogenética vegetal; Citometria de fluxo
• Palavras-chave em Inglês: Carica papaya; Somatic; Papaya; Plant cytogenetics; Flow cytometry
• Área do conhecimento CNPq: CNPQ::CIENCIAS BIOLOGICAS::GENETICA::GENETICA VEGETAL
• Link de acesso: http://locus.ufv.br/handle/123456789/4754

Somatic embryogenesis is an alternative technique of clonal micropropagation in Carica papaya, taking into account the problems generated by the conventional seed propagation and the absence of an effective method for early sex determination of this trioecious species. Considering the interest in large-scale seedlings production of papaya, liquid system and the use of immature zygotic embryos as explant source have proved to be more efficient for the somatic embryos generation in quickly way and in relatively high amount. However, tissue culture techniques are frequently associated with somaclonal variation ocorrence. Therefore, detection and selection of somaclones become necessary, and different methodologies have been employed for this purpose. In this perspective, this study adapted a protocol for mass production of somatic embryos in liquid medium and adopted cytometry and cytogenetics strategies for monitoring somaclonal variation in papaya. Firstly, immature zygotic embryos, which show a high embryogenic potential, were cultured in semi-solid médium, in the presence of 2,4-D, for friable embryogenic callus induction. The transfering of these callus to a liquid system, under the 2,4-D and BAP regulators action, allowed the increase of the cell aggregates proliferation. This auxin and cytokinin ratio was ideal for allowing only cell proliferation rather than differentiation of the suspensions in somatic embryos. These were converted and matured after inoculation of aggregates in liquid medium supplemented with ABA. In this condition, somatic embryos suspensions were obtained, in the early heart, torpedo, pre-cotyledonary and cotyledonary stages. Direct somatic embryogenesis, without callus formation, was also observed from the primary somatic embryos. Cotyledonary embryos were extracted and germinated on semi-solid medium containing GA3. About 80% of plantlets were regenerated and subjected to in vitro acclimatization. The potential of the flow cytometry technique could be demonstrated by verifying the ploidy level of regenerants and, thus, the evaluation of somaclonal variation occurrence. In this screening, diploid (88%), tetraploid (6%) and aneuploid (6%) seedlings were detected. For cytogenetic methodology, known diploid seedlings had their karyograms assembled, in which it did not observe any numerical or structural change. The association of flow cytometry and cytogenetics methodologies has proven effective for somaclonal variants characterization and the interest diploid seedlings selection for clonal propagation. Mainly, flow cytometry can be considered a viable technique for commercial purposes.