155 resultados para Explant


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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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A cagaiteira é uma espécie nativa do Cerrado com elevado potencial frutífero. Como suas sementes apresentam elevada variabilidade, sendo ainda recalcitrantes e dormentes, a germinação in vitro apresenta-se como uma alternativa para a propagação da espécie, além de permitir a obtenção de explantes juvenis para a micropropagação. Com presente trabalho, objetivou-se avaliar o efeito da escarificação e da luminosidade na germinação in vitro de sementes de cagaiteira. Sementes desprovidas do tegumento e sementes intactas foram inoculadas em meio MS e mantidas na ausência e presença de luz. Sementes desprovidas de tegumento germinadas tanto na presença quanto na ausência de luz apresentaram 86,25% e 88,25% de germinação aos 31 e 71 dias da inoculação, respectivamente. Após 150 dias de inoculação, plântulas provenientes de sementes desprovidas de tegumento, germinadas na presença e ausência de luminosidade, apresentaram 10% e 12% de anomalias, respectivamente.

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Byrsonima intermedia A. Juss. é uma planta medicinal e frutífera do Cerrado, cuja propagação convencional é difícil, devido à presença do endocarpo extremamente lignificado. Embora o hipoclorito de sódio (NaOCl) seja amplamente utilizado para a desinfestação superficial, existem poucos relatos de seus efeitos sobre o crescimento do explante. Neste trabalho, o objetivo foi estudar o efeito de diferentes pHs e períodos de exposição de sementes de B. intermedia em uma solução de NaOCl. As sementes foram submetidas a diferentes tempos de exposição (1, 5 e 10 minutos) numa solução de NaOCl com diferentes pHs (5, 7, 10 e 12) e, após o tratamento com hipoclorito de sódio, os embriões foram inoculados em meio WPM com a concentração de 50% de sais sem sacarose, ágar a 0,5% e pH 5,8 e, depois de 75 dias de cultivo, o crescimento das plântulas foi avaliado. A utilização de NaOCl é eficaz na desinfestação de sementes de B. intermedia, independente da variação do pH ou dos períodos de exposição. A porcentagem de plântulas normais, o comprimento da parte aérea e o número de folhas são positivamente afetados pela utilização de solução de NaOCl a pH de 8,5-8,9 ou pelo aumento do período de exposição, enquanto o número de raízes é afetado apenas pelo aumento do período de exposição na solução NaOCl.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Agronomia - FEIS

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Pós-graduação em Pesquisa e Desenvolvimento (Biotecnologia Médica) - FMB

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Dendrobium is a large genus in the family Orchidaceae that exhibits vast diversity in floral characteristics, which is of considerable importance to orchid breeders, biotechnologists and collectors. Native species have high value as a result of their medicinal properties, while their hybrids are important as ornamental commodities, either as cut flowers or potted plants and are thus veritable industrial crops. Thus, preservation of Dendrobium germplasm is valuable for species conservation, breeding programs and the floriculture industry. Cryopreservation represents the only safe, efficient and cost-effective long-term storage option to facilitate the conservation of genetic resources of plant species. This review highlights 16 years of literature related to the preservation of Dendrobium germplasm and comprises the most comprehensive assessment of thorough studies performed to date, which shows reliable and reproducible results. Air-drying, encapsulation-dehydration, encapsulation-vitrification, vitrification and droplet-vitrification are the current cryopreservation methodologies that have been used to cryopreserve Dendrobium germplasm. Mature seeds, pollen, protoplasts, shoot primordia, protocorms and somatic embryos or protocorm-like bodies (PLBs) have been cryopreserved with different levels of success. Encapsulation-vitrification and encapsulation-dehydration are the most used protocol, while PLBs represent the main explant explored.

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Amino acids play fundamental roles in plant morphogenesis. Among sources of organic nitrogen (N), glutamine has frequently been used during the establishment and maintenance of cell and tissue cultures. The aim of this study was analyse endogenous levels of glutamine during somatic and zygotic embryogenesis of Acca sellowiana (Feijoa or pineapple guava). The in vitro absorption of H-3-labelled glutamine was investigated. Zygotic embryos and embryogenic cultures (EC) were evaluated at 30 d and 70 d after explant inoculation onto the medium. Endogenous levels of glutamine were similar during zygotic and somatic embryogenesis, and showed a gradual decline until day-24 in culture. The highest rates of H-3-labelled glutamine uptake were observed during the first 2 h of incubation, resulting in values of 6.29 mu mol g(-1) fresh weight (FW) for zygotic embryos, 14.43 mu mol g(-1) FW for EC after 30 d, and 13.85 mu mol g(-1) FW for EC after 70 d. These results showed that the decreased levels of glutamine observed during the initial phase of development may be related to de novo protein synthesis and mobilisation during embryo maturation. The absorption of glutamine in the first 2 h of incubation also emphasises its involvement as an important source of N during morphogenesis of somatic and zygotic embryos.

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This study aimed to characterize the anatomical events and ultrastructural aspects of direct and indirect in vitro organogenesis in Passiflora edulis. Root explants were cultured on induction medium, supplemented with 4.44 mu M 6-benzyladenine. Roots at different stages of development were collected and processed for observation by light microscopy and scanning and transmission electron microscopy. Patterns of direct and indirect regeneration were observed in the explants. During direct organogenesis, the organogenic buds and nodules, formed from meristemoids, originated from the pericycle regions distant from the cut surface. Completely differentiated buds were observed after 20 days of culture. During indirect organogenesis, bud formation occurred via meristemoids at the periphery of the calli, which differentiated from the cortical region of the initial explant. Regardless of the regeneration pattern, the meristemoids had similar ultrastructural characteristics; however, differences were reported in the nuclear shape of the cells of the meristemoids formed directly and indirectly. This study provides important information for enhancing the understanding and characterization of the organogenic process in non-meristematic explants and provides information on the use of roots as explants in genetic transformation protocols for this important tropical species.

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The difficulty in adult tissue genetic transformation in woody species is still an obstacle to be overcome, including in most sweet orange cultivars of the Brazilian citrus industry. This work reports that, after in vitro culture adjustments, transgenic adventitious buds of 'Hamlin', 'Pra', and 'Valencia' sweet oranges (Citrus sinensis L. Osbeck) were recovered using adult material as explant source, in genetic transformation experiments via Agrobacterium tumefaciens. The transgenic buds were identified by the GUS histochemical analysis and confirmed by PCR analysis, which indicated the presence of an amplified fragment of 817 bp corresponding to the uidA gene sequence. The efficiencies of genetic transformation for 'Hamlin', 'Pra', and 'Valencia' sweet orange cultivars were 2.5, 1.4, and 3.7%, respectively. Media supplemented with auxins and cytokinins during co-culture, and media with high concentrations of cytokinins (3 mg L-1) during transgenic selection led to the transformation and, consequently, the regeneration of adequate number of adventitious buds for the three cultivars. The use of sonication during the explant disinfection was not effective to reduce endophytic contamination and reduced transformation efficiency.

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Rangpur lime (Citrus limonia Osbeck) in vitro organogenesis was studied based on explant type and cytokinin culture media supplementation. Four explants types collected from epicotyl or hypocotyl regions of in vitro germinated seedlings were evaluated. The epicotyl-derived explants consisted of epicotyl segments and the hypocotyl-derived explants consisted of the entire hypocotyl segment, the hypocotyl segment attached to a cotyledon fragment, and the hypocotyl segment divided longitudinally. The explants were cultured on EME culture medium supplemented with benzylaminopurine (0, 0.5, 1.0, or 1.5 mg L-1). The evaluation was performed after 6 weeks. Best results considering both the explant responsiveness and number of shoots developed per explants were obtained when epicotyl segments-derived explants were evaluated. Considering the explant responsiveness of hypocotyl segments-derived explants no difference was detected between the entire hypocotyl segment and the hypocotyl segment attached to a cotyledon fragment. Moreover, the percentage of responsive explants decreased when hypocotyl segments divided longitudinally were tested. No difference was detected for the number of shoots developed per explant considering the three types of hypocotyl-derived explants. Culture media supplementation with BAP was not essential for Rangpur lime in vitro organogenesis. However, adventitious shoot development was stimulated in concentrations between 0.5 - 1.0 mg L-1.