Lia Rosane Rodrigues

Origin of embryo-like structures in soybean anther culture investigated using SSR marker

The Satt418 microsatellite locus was examined in order to investigate the origin of embryo-like structures (ELS) obtained from soybean anther culture. Four heterozygous plants were used as anther donors. A total of 7000 anthers were placed on the induction medium under culture conditions known to trigger androgenic response. After 60 days of culture, upper portion of 216 ELS were carefully removed and transferred to a proliferation medium, in order to obtain sufficient tissue for DNA extraction. Callogenic masses originated from 114 ELS were screened for the Satt418 microsatellite locus. Heterozygous and homozygous ELS were identified, suggesting occurrence of somatic embryogenesis and androgenesis in the same system. This unexpected morphogenic response seems to be genotype-dependent.

Superação de dormência em sementes de Butia capitata

Aiming to identify efficient conditions to break dormancy in Butia capitata (Mart.) Becc. seeds sown in vitro and in an incubator tests were conducted with mechanical scarification in pre-sowing, by partial or total opening of the seed embryonic cavity, isolated of the endocarps. The embryonic cavity opening accelerated germination significantly, especially when there was total removal of the seed cap, allowing germination on average 90% of embryos, regardless of the provenance of the accessions. The seed dormancy of B. capitata seems to be related to the mechanical barrier imposed by the seed tissues that hamper the embryo development, suggesting mechanical exogenous dormancy.

Effects of light conditions and 2,4-D concentration in soybean anther culture

The morphogenic response of anther walls and connective tissue is the greatest obstacle to androgenesis in soybean anther culture. Whereas induction to microspore embryogenesis occurs in the dark in almost all plant species, soybean anthers have been cultured under light. In an attempt to establish culture conditions that simultaneously stimulate microspore embryogenesis and inhibit epidermal and connective cell proliferation, the effect of light and two 2,4-dichlorophenoxyacetic acid (2,4-D) concentrations (2 and 10 mg l−1) on the induction process was investigated. Higher 2,4-D concentration speeded up microspore plasmolysis and did not improve androgenesis. Callogenesis and embryogenesis induction from sporophytic cells were significantly lower in the dark, and some microspores showed major alterations in the sporoderm. Auxin 2,4-D and induction under light contributed to the morphogenic response of the anther walls and connective tissue under the conditions previously recommended to trigger microspore embryogenesis.

Histology of embryogenic responses in soybean anther culture

In order to clarify the embryogenic responses in soybean anther culture, anthers of four cultivars were cultured under known conditions to trigger androgenic response. A histological study was performed with anthers in vivo and with approximately 100 explants sampled after 9, 12, 15, 18, 21, 30 and 45 days of culture. In vitro culture triggered the frequent accumulation of phenolic compounds on the locular and anther surfaces, and also caused the destruction of cells and tissues in complex structure such as the tapetum, microspores and pollen grains. Somatic embryogenesis of unicellular origin was observed from the epidermis and the middle layer, and of multicellular origin from connective calluses. No androgenic response could be observed in the anthers of these four soybean genotypes, in the medium and conditions indicated. We point out to the need of changing the approach to the study of androgenesis in soybean, either by using culture conditions unfavourable to the proliferation of diploid tissues, or by culturing isolated microspores.

Qualidade fisiológica de sementes de guabijuzeiro (Myrcianthes pungens (Berg) Legrand - Myrtaceae) em armazenamento

Guabijuzeiro is a woody plant and occurs in Brazil, from the states of Sao Paulo until Rio Grande do Sul. Guabijuzeiro seeds are susceptible to dissection and present short longevity. The aim of this wotk was to evaluate the physiological quality of seeds throughout the course of eight months under cold chamber storage (5±1 oC and 80% RM). Seeds collected from six different plants, from Encruzilhada do Sul and Cachoeira do Sul districts in the state of Rio Grande do Sul, were evaluated in relation to moisture content, mass of 1000 seeds, germination, mean time to germination, emergence and mean time to emergence. Until the third month of storage, viability was higher than 50% and seeds from three progenies presented viability up to 75%. Low variation in moisture content (40 to 45%) was recorded during storage. The quality of the seeds from all origins decreased under storage, however after eight months, 56 to 61% of the seeds from two progenies remained viable. Thus, it is possible to extend longevity of guabijuzeiro seeds by means of cold chamber storage.

In vitro propagation of Limonium latifolium Kuntze (Plümbaginaceae)

Limonium latifolium Kuntze is a cut flower commercialy propagated in vitro. To develop and improve the micropropagation protocol, a sequence of assays was developed to evaluate performance of node explants; effect of cytokinins concentration (kinetin-KlN and 6-benzyl-aminopurin-BA) on the regeneration rate; the presence of BA during the multiplication phase; concentration of naphthaleneacetic acid-NAA and indole3-butyric acid-IBA on the rooting phase and procederes for the acciimatiwtion in vitro. The micropropagation was done at commercial levei using inflorescence nades explants. By the regeneration phase the best results were obtained with BA at 0.7mg/l for 35 days in MS medium. The multiplication phase takes 35 days and shows satisfactory results with BA at 0.2mg/l , with the rate of 4 plantiets/explant. The rooting phase is takes 30 days in MS medium with IBA at 1mg/l , with good survival scores after transfer to in vivo. The acciimatiwtion has made under plastic covering, inside greenhouse with room temperature and intermitent mist, using flats with 242 cells of 10cm3 each, filled with sterilized carbonized rice hulis. Every two weeks the plants were fertigated with commercial fertilizer (15:5:15 + micronutrients) at 0.5g/l . The in vitro process takes 100 - 120 days and one explant originates 15 - 30 plants.

Poliembrionia e número de sementes por fruto de quatro cultivares de tangerineira

Four mandarin cultivars were characterized for seed number per fruit and polyembryony, three of them are used as parents in the Departamento de Horticultura e Silvicultura - Universidade Federal do Rio Grande do Sul citrus breeding program. Mandarin fruits were sampled from the Experimental Station citrus collection, in Eldorado do Sul, RS, and their seeds were extracted and counted. In esterile chamber, the embryos were excised from seeds and cultured in vitro on MT medium (Murashige & Tucker, 1962), at 26±3°C with a 16h photoperiod. The mandarin cultivars Cai, Montenegrina (Citrus deliciosa Tenore), Ponca (C. reticulata Blanco) and King (C. nobilis Loureiro) had an average of 16, 14, 8 and 24 viable seeds per fruit, respectively, and 5.7, 5.7, 7.7 and 3.2 embryos per seed. Monoembryonyc seed production was low, except in King cultivar, which had 20.4% of monoembryonic seeds. Albine embryos were also detected, which were part or total content of some seeds. In general, the species showed significant differences in relation to the studied traits. The similarities between the C. deliciosa cultivars are strong evidences for the hipotesis that Montenegrina is originated from Cai.

Isolation and culture of soybean (Glycine max L. Merrill) microspores and pollen grains

In the last three decades, research on soybean microspore embryogenesis was restricted to anther culture, which presents limitations such as the small number of responsive microspores and the high embryogenic potential of sporophytic tissues. Therefore, a sequence of studies was performed to establish appropriate conditions for the isolation and culture of soybean microspores and pollen grains as an alternative to anther culture. First, a pollen and microspore isolation technique was developed using floral buds from four soybean cultivars (Bragg, IAS 5, MG/BR-46 Conquista and BRSMT Uirapuru). This technique allowed the establishment of cultures with satisfactory density and characteristics. Subsequently, different culture conditions were tested. Although B5 and MS media have been currently recommended for soybean anther culture, the best result was obtained in PTA-15 modified medium, with the formation of enlarged microspores and 0.4% of multicellular pollen grains in the cultivar BRSMT Uirapuru.