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Filho A.C.,Federal University of Santa Maria | Guadagnin J.P.,Fundacao Estadual de Pesquisa Agropecuaria FEPAGRO
Ciencia Rural | Year: 2011

The objective of this research was to evaluate the clustering pattern consistency obtained from the combination of the two dissimilarity measures and four clustering methods, in scenarios consist of combinations number of cultivars and number of variables, with real data in corn cultivars (Zea mays L.) and simulated data. We used real data from five variables measured in 69 trials involving corn cultivars, the number of cultivars ranged between 9 and 40. In order to investigate the results with more cultivars and variables, were simulated under the standard normal distribution, 1,000 experiments for each of the 54 scenarios formed by the combination among the number of cultivars (20, 30, 40, 50, 60, 70, 80, 90 and 100) and the number of variables (5, 6, 7, 8, 9 and 10). Analyses of correlation, diagnoses of multicollinearity ans cluster were carried out. Clustering pattern consistency was evaluated by the cophenetic correlation coefficient. There is a decrease of clustering pattern consistency with the increase in the number of cultivars and variable. The euclidean distance provides greater clustering pattern consistency in relation to Manhattan distance. The clustering pattern consistency among the methods increases as follows: Ward's, complete linkage, single linkage and average linkage between groups. Source


Filho A.C.,Federal University of Santa Maria | Storck L.,Federal University of Santa Maria | Guadagnin J.P.,Fundacao Estadual de Pesquisa Agropecuaria FEPAGRO
Ciencia Rural | Year: 2010

The aim of this research was to determine how many evaluations (replications) were necessary to predict the performance of corn (Zea mays L.) cultivars. Grain yield data were used, from 286 cultivar competition trials of corn, carried out in the Rio Grande do Sul State, Brazil, in the crop years of 2002/2003, 2003/2004, 2004/2005, 2005/2006, 2006/2007, 2007/2008 and 2008/2009. For each assay was carried out the analysis of variance, estimated the repeatability coefficient and calculated the number of replications needed to predict the real value of the cultivars, based on genotypic determination coefficient of 0.80 and 0.90. Assays with three and four replications are sufficient to identify superior cultivars of the corn, in relation to the grains yield, with respectively 72.40 and 81% accuracy of its real value. Source


Ambrosini A.,Federal University of Rio Grande do Sul | Beneduzi A.,Federal University of Rio Grande do Sul | Stefanski T.,Federal University of Rio Grande do Sul | Pinheiro F.G.,Federal University of Rio Grande do Sul | And 2 more authors.
Plant and Soil | Year: 2012

Background and Aims: This study was aimed at assessing the diversity of putatively diazotrophic rhizobacteria associated with sunflower (Helianthus annuus L.) cropped in the south of Brazil, and to examine key plant growth promotion (PGP) characteristics of the isolates for the purposes of increasing plant productivity. Methods: 299 strains were isolated from the roots and rhizosphere of sunflower cultivated in five different areas using N-free media. 16S rDNA PCR-RFLP and 16S rRNA partial sequencing were used for identification and the Shannon index was used to evaluate bacterial diversity. Production of siderophores and indolic compounds (ICs), as well phosphate solubilization activities of each isolate were also evaluated in vitro. On the basis of multiple PGP activities, eight isolates were selected and tested for their N-fixation ability, and their capacity as potential PGPR on sunflower plants was also assessed. Results: All except three Gram-positive strains (phylum Actinobacteria) belonged to the Gram-negative Proteobacteria subgroups [Gamma (167), Beta (78), and Alpha (50)] and the family Flavobacteriaceae (1)]. Shannon indexes ranged from 0.96 to 2.13 between the five sampling sites. Enterobacter and Burkholderia were the predominant genera isolated from roots and rhizosphere, respectively. Producers of siderophores and ICs were widely found amongst the isolates, but only 19.8% of them solubilized phosphate. About 8% of the isolates exhibited all three PGP traits, and these mostly belonged to the genus Burkholderia. Four isolates were able to stimulate the growth of sunflower plants under gnotobiotic conditions. Conclusions: Enterobacter and Burkholderia were the dominant rhizospheric bacterial genera associated with sunflower plants. Inoculation with isolates belonging to the genera Achromobacter, Chryseobacterium, Azospirillum, and Burkholderia had a stimulatory effect on plant growth. © 2012 Springer Science+Business Media B.V. Source


Filho A.C.,Federal University of Santa Maria | Guadagnin J.P.,Fundacao Estadual de Pesquisa Agropecuaria FEPAGRO
Revista Ciencia Agronomica | Year: 2011

It is important to know the number of replications to evaluate characters of corn cultivars with desired accuracy. The objective of this work was to determine how many evaluations (replications) necessary to evaluate characters of corn (Zea mays L.) cultivars. Data were collected from 16 cultivar competition trials of corn, carried out in the Rio Grande do Sul State, Brazil, in the crop years of 2002/2003, 2003/2004 and 2004/2005. In each experiment, it was used a randomized blocks design with three blocks or replications. The following characters were measured: number of days from sowing to 50% flowering male, plant and ear heights at harvest and the number of ears at harvest. Assumptions of the mathematical model were examined, analysis of variance was performed, the repeatability coefficient was estimated and the number of repetitions was calculated. Experiments with four replications are adequate to evaluate the characters number of days from sowing to 50% flowering male, plant height, ear height and the number of ears, with respectively 88.7; 75.1; 74.5 and 69.4% of accuracy. Source


Granada C.E.,Federal University of Rio Grande do Sul | Arruda L.,Fundacao Estadual de Pesquisa Agropecuaria FEPAGRO | Lisboa B.B.,Fundacao Estadual de Pesquisa Agropecuaria FEPAGRO | Passaglia L.M.P.,Federal University of Rio Grande do Sul | Vargas L.K.,Fundacao Estadual de Pesquisa Agropecuaria FEPAGRO
Biology and Fertility of Soils | Year: 2014

In this study, rhizobia strains isolated from white clover (Trifolium repens) root nodules were evaluated in an effort to identify an efficient nitrogen-fixing rhizobia strain that can also improve the growth of rice plants (Oryza sativa). White clover plants were collected from seven sites in south Brazil, and 78 native rhizobia isolates were obtained. The genetic diversity analysis of those isolates was carried out by BOX-polymerase chain reaction. Overall, the native rhizobia isolated showed a high genetic diversity, but when the bacterial isolates from the same site were compared, the diversity was lower. One native rhizobia, POA3 (isolated from the Porto Alegre locality), was able to promote the growth of both plants and is therefore a good candidate for new inoculant formulation. Finally, we can conclude that the community of native rhizobia symbiont of white clover plants in southern Brazil is highly diverse and the growth promotion effect of rhizobia inoculation on rice plants was more pronounced in a poor nutrient substrate condition than in a rich nutrient substrate condition. © 2013 Springer-Verlag Berlin Heidelberg. Source

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