RESUMO -(Germinabilidade de sementes de espécies endêmicas de Encholirium Mart. ex Schult. & Schult. f. e Dyckia Schult. & Schult. f. (Bromeliaceae) após dessecação, armazenamento e criopreservação). O armazenamento de sementes requer a determinação prévia das condições ótimas de temperatura e luz para a germinação, assim como da tolerância à dessecação e a baixas temperaturas. O objetivo deste trabalho foi o estudo do efeito da dessecação, armazenamento a baixa temperatura e criopreservação de seis espécies de Encholirium e duas de Dyckia, selecionadas de acordo com critérios de vulnerabilidade. A germinabilidade de sementes recém-coletadas variou entre 35 e 95%. As sementes apresentaram comportamento fotoblástico, uma vez que a presença de luz foi necessária para induzir a germinação ou aumentar sua eficiência. A dessecação não afetou significativamente a germinabilidade das sementes testadas, com exceção de E. heloisae e E. scrutor. Sementes dessecadas e armazenadas durante um ano a 4 e -20 °C não apresentaram alterações na germinabilidade, exceto em E. pedicellatum. A germinabilidade após congelamento em nitrogênio líquido foi maior que ou similar à obtida no controle, em todas as espécies estudadas. Entretanto, em E. pedicellatum a tolerância ao congelamento só foi obtida após dessecação das sementes a um conteúdo hídrico de 2,5%. Considerando a tolerância à dessecação e ao armazenamento em baixas temperaturas, as sementes estudadas podem ser classificadas como ortodoxas e conservadas ex situ. Palavras-chave: Cadeia do Espinhaço, conservação de sementes, criopreservação, germinação, sementes ortodoxasABSTRACT -(Germinability after desiccation, storage and cryopreservation of seeds from endemic Encholirium Mart. ex Schult. & Schult. f. and Dyckia Schult. & Schult. f. species (Bromeliaceae)). Seed storage procedures require previous determination of optimal temperature and light conditions for germination, as well as of tolerance to desiccation and low temperatures. The aim of this paper was to study the effects of desiccation, storage at low temperatures and cryopreservation on the germinability of seeds of six Encholirium and two Dyckia species, which were selected according to vulnerability criteria. Initial germinability of newly harvested seeds varied from 35 to 95%. Seeds presented photoblastic behaviour since light was necessary to induce or increase germination. Except for E. heloisae and E. scrutor, desiccation did not affect significantly the germinability of tested seeds. Storage for one year at 4 and -20 °C did not affect the germinability of desiccated seeds, except for E. pedicellatum. Germinability after freezing in liquid nitrogen was higher than or similar to control seeds for all species. However, freezing tolerance of E. pedicellatum seeds was only achieved after desiccation to 2.5% moisture content. As regards tolerance to desiccation and to storage at low temperatures, the seeds studied here can be classified as orthodox and conserved ex situ.
Arachis retusaKrapov. et W. C. Gregory et Valls is endemic in the West-central region of Brazil, occurring in areas endangered by human actions. The establishment of in vitro preservation methods for wild species of Arachis is an alternative to seed banks for germplasm storage, multiplication and distribution. The risk of genetic changes induced by tissue culture and the monitoring of the genetic stability of the biological material before, during and after storage must be considered in the context of conservation. Random amplified polymorphic DNA (RAPD) and amplified fragment length polymorphism (AFLP) fingerprinting were used to evaluate the genetic stability of in vitro plants originated from cotyledons and embryo axes of A. retusa. Cotyledons originated shoots through direct organogenesis and embryo axes displayed multishoot formation induced by 110 mmol/L and 8.8 mmol/L BAP, respectively. Ninety genomic regions (loci) generated from RAPD and 372 from AFLP analyses were evaluated. All amplified fragments detected by both techniques in plants derived from the two explant types were monomorphic. The results indicate that the recovered shoots are genetically stable at the assessed genomic regions. Key words: amplified fragment length polymorphism; Arachis retusa; in vitro preservation; micropropagation; random amplified polymorphic DNA; somaclonal variation. Gagliardi RF, Hanai LR, Pacheco G, Oliveira CA, Carneiro LA, Valls JFM, Mansur E, Vieira MLC (2007). Assessment of genetic stability among in vitro plants of Arachis retusa using RAPD and AFLP markers for germplasm preservation.
Somatic embryogenesis was induced from seed explants of Arachis archeri, A. porphyrocalix (Section Erectoides) and A. appressipila (Section Procumbentes) in response to 6-benzylaminopurine (BAP). Embryo axes first developed into single shoots in response to 4.4 lM BAP. Friable embryogenic calluses were produced from the hypocotyl region of these explants in response to different BAP concentrations. Embryonic leaflets also gave rise to friable calluses, but somatic embryos were only observed in explants of A. archeri and A. appressipila. Histological analyses revealed the presence of heart-shaped, torpedo and cotyledonary stages embryos, both as isolated and fused structures. A low frequency of embryo-to-plant conversion was achieved by inducing shoot development on medium solidified with 0.5% phytagel and supplemented with 1.5% or 3% sucrose. Rooting was induced on MS supplemented with indole-3-acetic acid (IAA).
Seed explants of A. stenosperma were cultured on MS medium supplemented with 6-benzylaminopurine with the aim of rescuing nonviable accessions stored in seed bank conditions. The regeneration potential of leaf explants from in vitro plants derived from embryonic axes was studied by using whole leaflets and leaflet segments. Explants were cultured on Murashige and Skoog (MS) medium supplemented with different concentrations of 6-benzylaminopurine and naphthalene acetic acid. Indirect organogenesis was observed in response to 6-benzylaminopurine, either alone or in association with naphthalene acetic acid, in both explant types. Media supplemented with naphthalene acetic acid as the sole growth regulator induced rhizogenesis in whole leaflets and leaflet segments, with subsequent shoot production directly from the roots.
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