Embryonic dormancy in seeds of Bactris gasipaes Kunth (peach-palm)

Bactris gasipaes is a domesticated palm whose fruits are of great importance for the Amazonian people and whose heart of palm is also receiving economic interest in other brazilian and Latin America regions. The aim of this study was verify embryonic dormancy and its correlation with first cataphyll emergence in B. gasipaes seeds collected from four plants at Manaus city and four others at Coari city, both in the Amazonas state, Brazil. After extraction and cleaning, some of the seeds (4 replications of 25 per plant) were sown in a seedbed with a sawdust and sand mixture as substrate, and embryos (4 replications of 10 per plant), after extraction, were inoculated into half strength Murashige and Skoog cultures. Were used 100 seeds and 40 embryo per treatment. Whole seed and embryo germination varied between the different source plants and locations, with the greatest difference observed for the emergence of first cataphyll from seeds in the seedbed. For the most part of variables, results of seed and embryo were positively associated, namely, as one went up the other also, and vice versa. These results suggesting that, at least in part, seed dormancy in Bactris gasipaes is associated with embryonic dormancy. © 2017, Associacao Brasileira de Tecnologia de Sementes. All rights reserved

Isozyme characterization of Eucalyptus urophylla (S.T. Blake) and E-grandis (Hill ex Maiden) populations in Brazil

Seedling taken from 2 species of Eucalyptus growing in Brazil were electrophoretically analysed at 14 isozyme loci representing 6 enzyme systems: alpha-EST, beta-EST, SKDH, IDH, MDH, and LAP. Genetic variability measures were determined using 11 putative isozyme loci. on average, 81.8% and 54.5% of the loci were found to be polymorphic by the criterion of 95% in E. urophylla and E. grandis, respectively. The mean number of alleles per loci was 3.0 in E. urophylla and 2.5 in E. grandis. Observed mean heterozygosity was 0.283 in E. urophylla and 0.166 in E. grandis. Levels of genetic diversity in these species were similar to those in other Eucalyptus species which have widespread distributions. The possible hybridization of E. urophylla with E. alba is also discussed

Genetic diversity of three size classes of seeds of Eucalyptus globulus ssp. globulus

Variation in seed size is often observed in samples of eucalypt seeds and this leads to heterogeneous populations of plants, principally through variation in the early stages of plant development. It follows that samples of seeds more uniform in size could produce more uniform populations of plants. In studies of Eucalyptus globulus ssp. globulus it was of interest to determine whether or not the genetic diversity within a population, through the use of isozyme markers, was altered in the subpopulations developed from seeds of different size classes. A commercial sample of seed was separated by seed size into three subpopulations and the percentage germination and mean fresh weight of the seedlings were determined. Proteins extracted from leaves of the seedlings were separated by electrophoresis and tested for activity of eight different enzymes. These eight enzymes showed activity at 20 loci and mean genetic diversity and fixation index were determined using 13 of these loci. The subpopulation of the smallest seeds contained a greater proportion of abnormal seeds and had a lower percentage germination and plant weight compared to the other subpopulations. No significant differences were found in the number of alleles per locus, percentage of polymorphic loci, mean heterozygosity. The major part of the endogamy, indicated by F statistic, was found within the subpopulations: F-(IS) = 0.518; F-(ST) = 0.010 and F(IT) = 0.523. We conclude that the use of seeds of uniform size will lead to more uniform germination and plant growth without alteration in overall genetic diversity

Variabilidade genetica em populacoes de algaroba (Prosopis juliflora (SW). DC.) na regiao semi-arida do Nordeste.

O genero Prosopis (Leguminosaea, Mimosoideae) compreende em torno 44 especies e sua ocorrencia natural abrange principalmente a America do Norte, e America do Sul mas tambem, ha relatos da ocorrencia de algumas especies na Africa e na Asia. Sao especies, que tem habito de crescimento que variam desde arbustos a arvores e tambem na forma de ervas lenhosas. Em geral, crescem em regioes subtropicais com regimes de precipitacao que variam de 200 - 800 mm com um pronunciado periodo de seca.Na regiao semi-arida do Nordeste, uma das especies, a Prosopis juliflora (SW). DC. introduzida na decada de 40, tem se destacado por sua importancia economica tendo em vista, seu uso multiplo (lenha, carvao, sombreamento, alimentacao animal). No entanto, faltam estudos mais detalhados que possibilitem estimar a variabilidade genetica das populacoes existentes para a conducao de programas de melhoramento genetico. Para estimar a variabilidade genetica, foram utilizados marcadores bioquimicos (isoenzimas). Os materiais geneticos estudados, representam cinco populacoes de algaroba de diferentes procedencias cuja amostragem, envolveu 20-30 matrizes por populacao. A partir da coleta dos frutos e extracao das sementes, produziram-se plantulas das quais foram utilizadas flhas cotiledonares com 10 dias de idade, nas analises eletroforeticas. Foram testados 17 sistemas isoenzimaticos em diferentes sistemas tampao gel-eletrodo: Tris-Citrato, pH 7,5, Tris-Citrato Borato, pH 8,3 e Citrato de Morfolina, pH 6,1 tendo como meio suporte, gel de (...