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Dive into the research topics where Valdir Marcos Stefenon is active.

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Featured researches published by Valdir Marcos Stefenon.


Biodiversity and Conservation | 2009

Integrating approaches towards the conservation of forest genetic resources: a case study of Araucaria angustifolia.

Valdir Marcos Stefenon; Neusa Steiner; Miguel Pedro Guerra; Rubens Onofre Nodari

In the past years the conservation of forest genetic resources has been widely recognized because of the risk of adverse effects associated with global changes in the environment. Since little effort has been made towards conservation of these resources, the assessment and the integration of information and knowledge so far generated are valuable tools in order to promote their conservation. In the present work the Brazilian conifer Araucaria angustifolia was used as a case study, integrating information, published between 1980 and 2007, about genetics, biotechnology, palaeobotany, and archeology. These studies were interpreted towards the conservation needs and strategies of the species germplasm. The main conclusions for the conservation of A. angustifolia genetic resources are: (1) despite the reduction of genetic diversity by unsustainable forest exploitation, the genetic system of A. angustifolia seems to be efficient to protect this species against rapid losses of its genetic diversity; (2) conservation measures starting now may be efficient, since the genetic structures of existing populations is more largely influenced by the past evolutionary process than by human disturbance occurred in the last century; (3) there are opportunities to save the genetic resources of the species, if simple measures are taken to safeguard the continued existence of the few remaining araucaria forests. Emerged as a general conclusion that the use of sound scientific arguments supported by different areas of the science could be a very powerful instrument in persuading decision-makers, also by governments, taking into account forest genetic resources as a primary issue for the future.


Tree Genetics & Genomes | 2015

Genetic structure and internal gene flow in populations of Schinus molle (Anacardiaceae) in the Brazilian Pampa

Rafael Plá Matielo Lemos; Cristiane Barbosa D Oliveira; Valdir Marcos Stefenon

One of the most important aspects for population ecology and evolution is to understand the connectivity between individuals and their groups. In this study, amplified fragment length polymorphism (AFLP) markers were employed aiming to examine genetic diversity, spatial genetic structure, and internal gene flow of nine populations of Schinus molle across the Brazilian Pampa. The dispersal capacity of S. molle in the Brazilian Pampa, the implications of the forest fragmentation to species genetic structure, and the impact of the actual genetic structure of the species to its conservation and management were investigated. AFLP markers revealed low genetic diversity and clear genetic structure among populations. Significant fine-scale spatial genetic structure at short distances was observed in all populations. Estimates of gene dispersal distance suggest that the dispersion capacity of this species is larger than the area covered by the studied populations. However, fragmentation hampers the gene flow among populations. The management of S. molle natural occurrence in this biome seems to be simple considering the species plasticity. The conservation of the species genetic resource depends on maintaining the extant forest patches and promoting their connectivity.


Genetica | 2015

Historical gene flow within and among populations of Luehea divaricata in the Brazilian Pampa

Jordana Nagel; Denise Ester Ceconi; Igor Poletto; Valdir Marcos Stefenon

Within and among population gene flow is a central aspect of the evolutionary history of ecosystems and essential for the potential for adaptive evolution of populations. We employed nuclear microsatellite markers to assess inter- and intra-population gene flow in five natural populations of Luehea divaricata growing in the Pampa biome, in southern Brazil. This species occurs in practically all secondary forests of the Pampa and has recognized ecological significance for these formations. The genetic structuring of the studied populations suggests limited gene dispersal among forest fragments, despite a homogeneous level of migration among populations. Notwithstanding the gene flow among populations, significant SGS is still found in some fragments. Significant spatial genetic structure within population was also found likely as result of limited seed and/or pollen dispersal. The scattered distribution of the populations and their relatively high density seem to limit pollen dispersal. Also seed dispersal by wind is not efficient due to large distances among forest formations. As conservationist actions towards preserving the genetic resources of L. divaricata and the Brazilian Pampa, we suggest the protection of the existing forest formations and the maintenance of the natural expansion of the forests over the grasslands in the biome.


Anais Da Academia Brasileira De Ciencias | 2015

Conservation of Forest Biodiversity: how sample size affects the estimation of genetic parameters

Leonardo Severo da Costa; Nathana Da Silva Corneleo; Valdir Marcos Stefenon

Efficient designs are crucial for population genetic studies on forest species. In this study we employed individual based simulations aiming to evaluate what fraction of a population should be sampled to obtain confident estimations of allelic richness and of inbreeding coefficient in population genetic surveys. The simulations suggest that at least 10% of the total population has to be sampled to ensure reliable estimations of allelic richness and inbreeding coefficient. This approach will allow the confidence of the genetic parameters estimations of a larger number of populations, based on a minimal sample within each one.


Anais Da Academia Brasileira De Ciencias | 2009

Monoicy in A. angustifolia (Bert.) O. Kuntze (Araucariaceae): I. Morphological aspects of the reproductive structures

Valdir Marcos Stefenon; Clarissa Alves Caprestano

Araucaria angustifolia (Bert.) O. Kuntze is a dioecious conifer species native of Brazil. The rare occurrence of monoiceous specimens have been attributed to pathogenic infections or other injuries in adult trees. Here, the morphological characteristics of male and female cones and pollen grains of a monoiceous A. angustifolia are described. Male and female cones and pollen grains presented normal morphology, lacking any sort of injuries or infection and suggesting the existence of further grounds for the occurrence of monoicy in this conifer species.


Journal of Advances in Microbiology | 2017

Soil Bioremediation in Heavy Metal Contaminated Mining Areas: A Microbiological/Biotechnological Point of View

Jéssica Dutra Vieira; Valdir Marcos Stefenon

Bioremediation concerns the use of plants and microorganisms or their parts, for the decontamination and recuperation of polluted areas. The improvement of the bioremediation techniques is possible due to the last decade advances of the microbiological and biotechnological knowledge and methods. This study aimed to shortly review and discuss the bioremediation of mining areas contaminated with heavy metals focusing in some microbiological and biotechnological techniques. Strategies considered to be important on further studies are also presented. Mini-review Article Vieira and Stefenon; JAMB, 4(1): 1-10, 2017; Article no.JAMB.33782 2


Pesquisa Agropecuaria Brasileira | 2015

Germination and development of pecan cultivar seedlings by seed stratification

Igor Poletto; Marlove Fátima Brião Muniz; Tales Poletto; Valdir Marcos Stefenon; Carine Baggiotto; Denise Ester Ceconi

The objective of this work was to evaluate the effect of seed stratification on germination rate, germination speed, and initial development of seedlings of six pecan ( Carya illinoinensis ) cultivars under subtropical climatic conditions in southern Brazil. For stratification, the seeds were placed in boxes with moist sand, in a cold chamber at 4°C, for 90 days. In the fourteenth week after sowing, the emergence speed index, total emergence, plant height, stem diameter, and number of leaves were evaluated. Seed stratification significantly improves the germination potential and morphological traits of the evaluated cultivars.


Revista Monografias Ambientais | 2012

A EDUCAÇÃO AMBIENTAL NO AMBIENTE ESCOLAR COMO AUXILIADORA NA FORMAÇÃO DE EDUCANDOS CIDADÃOS

Julianne Marçal Munhoz; Gisele Lángaro Soares; Ana Claudia Silveira Ribeiro; Ticiana Fagundes da Porciuncula de Vilhena; Valdir Marcos Stefenon

The article discusses aspects of education perceived by researchers in a school in elementary school about the quality of life in the school environment and relevance of these aspects in the formation and construction of citizen learners. To this end, activities were primarily developed as survey questionnaires and games. Later, emphasizing the areas of Natural Sciences, actions have been addressed, demonstrating a lack of issues of Environmental Education, by the students, weakening the construction of critical and active citizens in the middle where they live.


Tropical Conservation Science | 2018

Genetic Diversity and Structure of Syagrus romanzoffiana (Cham.) Glassman (Arecaceae) in Southern Brazil

Bruna Lucia Laindorf; Karine de Freitas; Fabiola Lucini; Valdir Marcos Stefenon; Mariele Cristine Tesche Küster; Adriano Luis Schünemann; Jair Putzke; Filipe de Carvalho Victoria; Antonio Batista Pereira

The species Syagrus romanzoffiana is a monocot belonging to the family Arecaceae; it is a palm endemic to South America and is widely distributed throughout the southeast and south of Brazil, including the State of Rio Grande do Sul. To estimate the genetic diversity and structure of the species in the watersheds of Rio Grande do Sul, five simple sequence repeat markers were used to analyze 90 individuals, representing three populations. The genetic structure of S. romanzoffiana groups was evaluated through the analysis of molecular variance and a multivariate analysis based on Nei’s genetic distance. The evaluated populations showed significant intrapopulation molecular variation (FST = 0.11). The observed heterozygosity (HO = 0.17) was lower than the expected heterozygosity (HE = 0.75). These data indicate that although the number of individuals is high, the diversity is low for some indices. Our findings suggest that further studies are needed, particularly on the genetics of natural populations of S. romanzoffiana in Rio Grande do Sul State, to fully characterize their genetic diversity and structure and determine strategies and priority areas for species conservation.


International Journal of Legal Medicine | 2018

13-loci STR multiplex system for Brazilian seized samples of marijuana: individualization and origin differentiation

Mauro Sander Fett; Roberta Fogliatto Mariot; Eduardo Avila; Clarice Sampaio Alho; Valdir Marcos Stefenon; Flávio Anastácio de Oliveira Camargo

It is known that Cannabis in Brazil could either originate from Paraguay or be cultivated in Brazil. While consumer markets in the North and Northeast regions are maintained by national production, the rest of the country is supplied with Cannabis from Paraguay. However, the Brazilian Federal Police (BFP) has exponentially increased the seizure number of Cannabis seeds sent by mail. For this reason, the aim of the study was to assess the 13-loci short tandem repeat (STR) multiplex system proposed by Houston et al. (2015) to evaluate the power of such markers in individualization and origin differentiation of Cannabis sativa samples seized in Brazil by the BFP. To do so, 72 Cannabis samples seized in Brazil by BFP were analyzed. The principal coordinate analysis (PCoA) and probability identity (PI) analysis were computed. Additionally, the Cannabis samples’ genotypes were subjected to comparison by Kruskal-Wallis H, followed by a multiple discriminant analysis (MDA). All samples analyzed revealed a distinct genetic profile. PCoA clearly discriminated the seizure sets based on their geographic origin. A combination of seven loci was enough to differentiate samples’ genotypes, and the PI for a random sample is approximately one in 50 billion. The Cannabis samples were 100% correct as classified by Kruskal-Wallis H, followed by an MDA. The results of this study demonstrate that the 13-loci STR multiplex system successfully achieved the aim of sample individualization and origin differentiation and suggest that it could be a useful tool to help BFP intelligence in tracing back-trade routes.

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Rayssa Garay Medina

Universidade Federal do Pampa

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Jéssica Dutra Vieira

Universidade Federal do Pampa

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Rafael Tresbach

Universidade Federal do Pampa

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Deise Schroder Sarzi

Universidade Federal do Pampa

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