Universidade Estadual de Londrina

About: Universidade Estadual de Londrina is a education organization based out in Londrina, Brazil. It is known for research contribution in the topics: Population & Context (language use). The organization has 13052 authors who have published 19291 publications receiving 212123 citations.

Método do Perfil Cultural para avaliação do estado físico de solos em condições tropicais

Abstract: A new approach is discussed for adoption of criteria in the application of the cultural profile methodology for tropical soil conditions. The evolution of this methodology has been analyzed since its beginning in France in the 1960s, until its proposal for tropical soil management studies. The cultural profile approach can be used to make qualitative diagnosis of the physical state of soil in the field, as well as to help with soil sampling, to study the effect of agricultural machinery, to visualize the physical, chemical and biological soil interactions, and to help with the studies of contraction, expansion, and shearing in the field and in the structural organization of soils and root system analyses.

Holocentromeres in Rhynchospora are associated with genome-wide centromere-specific repeat arrays interspersed among euchromatin

Abstract: Holocentric chromosomes lack a primary constriction, in contrast to monocentrics. They form kinetochores distributed along almost the entire poleward surface of the chromatids, to which spindle fibers attach. No centromere-specific DNA sequence has been found for any holocentric organism studied so far. It was proposed that centromeric repeats, typical for many monocentric species, could not occur in holocentrics, most likely because of differences in the centromere organization. Here we show that the holokinetic centromeres of the Cyperaceae Rhynchospora pubera are highly enriched by a centromeric histone H3 variant-interacting centromere-specific satellite family designated “Tyba” and by centromeric retrotransposons (i.e., CRRh) occurring as genome-wide interspersed arrays. Centromeric arrays vary in length from 3 to 16 kb and are intermingled with gene-coding sequences and transposable elements. We show that holocentromeres of metaphase chromosomes are composed of multiple centromeric units rather than possessing a diffuse organization, thus favoring the polycentric model. A cell-cycle–dependent shuffling of multiple centromeric units results in the formation of functional (poly)centromeres during mitosis. The genome-wide distribution of centromeric repeat arrays interspersing the euchromatin provides a previously unidentified type of centromeric chromatin organization among eukaryotes. Thus, different types of holocentromeres exist in different species, namely with and without centromeric repetitive sequences.

Effects of Maytenus ilicifolia Mart. and Bauhinia candicans Benth infusions on onion root-tip and rat bone-marrow cells

Abstract: Medicinal plants are widely used to treat various diseases, and in Brazil the plants Maytenus ilicifolia Mart. and Bauhinia candicans Benth are commonly used in popular medicine. However, there are a large number of compounds in plants which can produce alterations in genetic material, and this study was conducted to investigate any possible mutagenic and cytotoxic effects that M. ilicifolia and B. candicans infusions may have on the cell cycle and chromosomes. Infusions were prepared with in natura leaves to give two concentrations of infusions, one at the concentration normally used by the population in general and the other at 10 times this value (i.e. 3.5 and 35 mg/mL for M. ilicifolia and 0.465 and 4.65 mg/mL for B. candicans). Onion (Allium cepa L.) root-tip cells (RTC) and Wistar rat bone-marrow cells (BMC) were used as test systems in in vivo assays. The M. ilicifolia infusions at both concentrations, and the B. candicans infusion at the lower concentration, had no statistically significant depressive mitotic effect on RTC. A statistically significant depressive mitotic effect on RTC was found with the more concentrated (4.65 mg/mL) B. candicans infusion as compared with a negative control. In BMC, infusions of B. candicans and M. ilicifolia produced no statistically significant increase in the number of chromosome alterations or rates of cell division as compared to controls. The significance of these findings are discussed in the light of the use of these plants as therapeutic agents.

Genotypic diversity among brazilian isolates of Macrophomina phaseolina revealed by RAPD

Abstract: Macrophomina phaseolina has been considered one of the most prevalent soybean (Glycine max) pathogens in Brazil. No genetic resistance has been determined in soybean and very little is known about the genetic diversity of this pathogen in tropical and sub-tropical regions. Fifty-five isolates from soybean roots were collected in different regions and analyzed through RAPD for genetic diversity. The UPGMA cluster analysis for 74 loci scored permitted identification of three divergent groups with an average similarity of 99%, 92% and 88%, respectively. The three groups corresponded to 5.45%, 59.95% and 34.6%, respectively of all isolates used. A single plant had three different haplotypes, while 10.9% of the analyzed plants had two different haplotypes. In another study the genetic similarity was evaluated among isolates from different hosts [soybean, sorghum (Sorghum bicolor), sunflower (Helianthus annuus), cowpea (Vigna unguiculata), corn (Zea mays) and wheat (Triticum aestivum)] as well as two soil samples from native areas. Results showed that more divergent isolates originated from areas with a single crop. Isolates from areas with crop rotation were less divergent, showing high similarity values and consequently formed the largest group. Amplification of the ITS region using primers ITS1 and ITS4 produced only one DNA fragment of 620 bp. None of the isolates were differentiated through PCR-RFLP. Our results demonstrated genetic variability among Brazilian isolates of M. phaseolina and showed that one single root can harbor more than one haplotype. Moreover, cultivation with crop rotation tends to induce less specialization of the pathogen isolates. Knowledge of this variation may be useful in screening soybean genotypes for resistance to charcoal rot.