ResumoA realização de metodologias cruzamentos é uma importante atividade no desenvolvimento programas melhoramento florestal, em razão da necessidade do incremento das características genéticas e qualidade na produção espécies frutíferas. Diante disso, considerando o potencial frutífero espécie Psidium cattleyanum (Araçá-Amarelo), esta pesquisa teve como objetivo estabelecimento técnicas nesta...

Hybridization between tetraploids and their related diploids is generally unsuccessful in Centaurea, hence natural formation of triploid hybrids is rare. In contrast, the diploid Centaurea aspera and the allotetraploid C. seridis coexist in several contact zones where a high frequency of triploid hybrids is found. We analyzed the floral biology of the three taxa to identify reproductive isolati...

BACKGROUND Epipactis helleborine is an Eurasian orchid species which prefers woodland environments but it may also spontaneously and successfully colonise human-made artificial and disturbed habitats such as roadsides, town parks and gardens. It is suggested that orchids colonising anthropogenic habitats are characterised by a specific set of features (e.g., large plant size, fast flower produc...

After treatment with nitrosoguanidine a mutation to temperature sensitivity was obtained in Tetrahymena pyriformis, syngen 1. The trait is controlled by a recessive allele, ts, at a locus linked to serotype locus T. I S is completely recessive, unlike any other allele studied in this organism, and the heterozygotes do not show vegetative assortment. The cross which revealed the linkage of ts an...

Whereas each of the two c9mplementary mating types, 0 and E, of Paramecium tetraulrelia normally shows cytoplasmic inheritance, an abnormal heredity of mating type was observed in the progeny of crosses between two stocks of different geographical origin of Paramecium tetraurelia (stock 51 and stock 32). The modified pattern of mating-type inheritance was shown to result from the interaction of...

REVIOUS evidence has shown (KIMBALL, GAITHER and PERDUE 1957,1961; 'KIMBALL, GAITHER and WILSON 1959) that most of the X-ray induced mutations detected by inviability and slow growth after autogamy in Paramecium aurelia originate from reparable premutational lesions. These lesions are subject to repair until the chromosomes duplicate, and only then are they fixed as final mutation. Chromosomal ...

yield is estimated between 4000 and 5000 kg/ha (Gepts, 1993). Low yields can be attributed in part to the poor The diversity, structure, genetic flow, and evolutive relationships knowledge and limited use of the genetic diversity of within and among three wild–weedy–domesticated complexes and a wild populations of this species (Gepts and Debouck, wild population isolated from crops of common be...

ATING type inheritance in Paramecium aurelia is an important example of permanent nuclear differentiation. The relevance of nuclear differentiation to the general problem of gene action and development has often been noted (e.g., see SONNEBORN 1960). Briefly, the study of mating type determination in P. aurelia (and other ciliates) has provided models of the limitation of genic potentiality and...

Trichomonades from the mouth were studied by Steinberg who proposed to group them into three distinct types; namely, Trichomonas elongata, Trichomonas caudata, and Trichomonas flagellata. Doflein (3) regards them as probably identical with Trichomonas hominis. Opinions differ as to whether or not Trichomonas vaginalis Donné and Trichomonas hominis Grassi are the same species. Lynch, for instanc...

a radically different answer to the specificity problem. Epigenetic phenomena are widespread among widely The d48 Paradigm: A Maternally Inherited divergent eukaryotes. They have most often been reSomatic Mutation vealed by their effects on gene expression, and indicate The first evidence of an epigenetic regulation of rethat identical genomic sequences can be stably mainarrangement patterns ca...