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Search Results: 1 - 10 of 601580 matches for " R.A.;Lamego "
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Resistência ao glyphosate em biótipos de Conyza bonariensis e Conyza canadensis no Estado do Rio Grande do Sul, Brasil
Lamego, F.P.;Vidal, R.A.;
Planta Daninha , 2008, DOI: 10.1590/S0100-83582008000200024
Abstract: dose-response experiments were conducted to evaluate the occurrence of resistance to glyphosate in conyza canadensis and conyza bonariensis biotypes originated from rio grande do sul counties. for each species, one experiment was conducted with two biotypes, one susceptible and one suspected of resistance. glyphosate rates of 0, 100, 200, 300, 400, 800 and 1200 g ha-1 were sprayed on the plants after reaching the 8-10 leaf growth stage. sigmoidal curves were adjusted to each biotype tested. resistance to glyphosate was confirmed for biotypes of both species with resistance factor of 2.3.
Competitiveness of ALS inhibitors resistant and susceptible biotypes of Greater Beggarticks (Bidens subalternans)
Lamego, F.P.;Vidal, R.A.;Burgos, N.R.;
Planta Daninha , 2011, DOI: 10.1590/S0100-83582011000200024
Abstract: the continuous use of als-inhibiting herbicides has led to the evolution of herbicide-resistant weeds worldwide. greater beggarticks is one of the most troublesome weeds found in the soybean production system in brazil. recently, a greater beggarticks biotype that is resistant (r) to als inhibitors due to trp574leu mutation in the als gene was identified. also, the adaptive traits between susceptible (s) and r to als inhibitors biotypes of greater beggarticks were compared. specifically, we aimed to: (1) evaluate and compare the relative growth rates (rgr) between the biotypes; (2) analyze the seed germination characteristics of r and s biotypes under different temperature conditions; and (3) evaluate their competitive ability in a replacement series study. the experiments were conducted at the university of arkansas, usa, in 2007 and at universidade federal do rio grande do sul (federal university of rio grande do sul), brazil, in 2008. plant proportions for replacement series studies were respectively 100:0, 75:25, 50:50, 25:75 and 0:100, with a total population of 150 plants m-2. there was no difference in rgr between r and s biotypes. the r-biotype germination rate was lower than that of the s biotype. however, at low temperature conditions (15 oc), the reverse was observed. in general, there is no difference in the competitive ability between r and s greater beggarticks biotypes.
Tolerancia à interferência de plantas competidoras e habilidade de supress?o por cultivares de soja: I. Resposta de variáveis de crescimento
Lamego, F.P.;Fleck, N.G.;Bianchi, M.A.;Vidal, R.A.;
Planta Daninha , 2005, DOI: 10.1590/S0100-83582005000300003
Abstract: differential morphological plant characteristics may influence competition relations between crop and weeds. the aim of this study was to evaluate the influence of plants of four soybean cultivars and two other soybean cultivars, mimicking dicotyledonous weed species, on their relationships during the vegetative growth period. thus, two experiments were carried out: one in pots, to provide data for initial soybean plant growth; and the other in the field, to monitor plant growth characteristics. the following factors and treatments were tested in the field: three competition conditions (absence of competing plants or presence of the soybean cultivars brs 205 or cobb), and four soybean cultivars reagent to competition (ias 5, br-16, cd 205, and fepagro rs-10). soybean cultivars showed varied emergence speed and initial plant growth. the presence of the concurrent plants, regardless of their plant characteristics, affected soybean branching. fepagro rs-10 and br-16 cultivars had a fast growth during the initial development period; cd 205, on the contrary, showed slow growth during this phase. early maturity soybean cultivars cover the soil more rapidly than late maturity cultivars, during the first 45 days of growth.
Diagnóstico da resistência aos herbicidas em plantas daninhas
Vidal, R.A.;Lamego, F.P.;Trezzi, M.M.;
Planta Daninha , 2006, DOI: 10.1590/S0100-83582006000300024
Abstract: weed resistance to herbicides is an evolutive phenomenon caused by the selection imposed by the herbicides. this serious problem has been increasing in the last years in agricultural areas. prevention through alternative management methods delays the appearance of resistant weeds. however, periodic monitoring of farmlands is the best way to avoid the spreading of the selected resistance biotypes. fast, efficient and precise diagnosis methods are useful in the confirmation of resistance cases avoiding seed dissemination. different methods have been developed in the last years seeking to improve resistance diagnosis. recent methods developed through biotechnology have been improved and are promising methods for herbicide resistant weed detection.
Resistência de Eleusine indica aos inibidores de ACCase
Vidal, R.A.;Portes, E.S.;Lamego, F.P.;Trezzi, M.M.;
Planta Daninha , 2006, DOI: 10.1590/S0100-83582006000100021
Abstract: among the causes for weed control inefficacy, the worst one is resistance to herbicides. the objectives of this work were to evaluate an eleusine indica biotype suspected of resistance to accase inhibitors and to investigate the occurrence of cross- resistance to several accase inhibitors. one biotype of eleusine indica originated from mato grosso with suspected resistance to accase inhibitors was evaluated in a greenhouse in relation to its susceptibility to several products of the ariloxyphenoxypropionate and cyclohexanedione groups. studies on dose response confirmed that the suspected biotype was 18 times more insensitive to sethoxydim than the susceptible biotype that had never been treated with herbicides. cross-resistance was confirmed for fenoxaprop, cyhalofop, propaquizafop and butroxydim. no cross-resistance was observed with fluazifop, haloxyfop, quizalofop, and clethodim.
Similaridade genética entre acessos de Bidens pilosa resistentes aos herbicidas inibidores da ALS
Vidal, R.A.;Lamego, F.P.;Resende, L.V.;Da-Silva, P.R.;Delatorre, C.A.;Trezzi, M.M.;
Planta Daninha , 2005, DOI: 10.1590/S0100-83582005000300020
Abstract: acetolactate synthase (als)-inhibiting herbicides have been widely used to control the weed hairy beggarticks (bidens pilosa). the selection pressure caused by intensive herbicide use has selected hairy beggarticks resistant biotypes. the objectives of this work were to evaluate the degree of genetic similarity among hairy beggarticks accesses (bidens pilosa) resistant to als-inhibiting herbicides, and to evaluate the relation between genetic similarity and geographic distance. seeds of two groups of hairy beggarticks accesses resistant to als-inhibitors were sampled from a farm at pato branco, paraná, and seedlings were grown in the greenhouse at the universidade federal do rio grande do sul (ufrgs), porto alegre, rs, in ocober/2004. the use of rapd (random amplified polymorphic dna) molecular markers allowed evaluating the genetic similarity among hairy beggarticks accesses. in the analysis of both access groups, out of twenty primers assessed, only seventeen displayed polymorphism and amplified a total of 94 bands. there is low genetic similarity (38%) among hairy beggarticks accesses resistant to als inhibitors from the same farm. there is no relationship between genetic distance and geographic distance in the evaluated accesses.
Impacto da temperatura, irradiancia e profundidade das sementes na emergência e germina??o de Conyza bonariensis e Conyza canadensis resistentes ao glyphosate
Vidal, R.A.;Kalsing, A.;Goulart, I.C.G.R.;Lamego, F.P.;Christoffoleti, P.J.;
Planta Daninha , 2007, DOI: 10.1590/S0100-83582007000200010
Abstract: intense glyphosate use either in orchards or specially no-tilled glyphosate-resistant soybeans, has selected resistant biotypes of both conyza bonariensis and c. canadensis. studies of the species biology could provide insight for integrated weed management. a research program was designed to evaluate how seed germination of both species was affected by the following factors: biotype, substrate composition, soil depth, temperature and light. a factorial arrangement of the treatments was established for the first experiment, where factor a consisted of biotypes (two from each species); factor b was substrate composition (soil, sand, soil: sand); and factor c was substrate depths (0, 0.5, 1, 2, 5 cm). the second experiment included the first factor; plus factor b as temperature (constant 20, 25, or 30 oc, and alternating 20/30 oc), and factor c as light conditions (light, dark). in a third experiment, factors consisted of species and temperature (10, 15, 20, 25, 30 oc). seedling emergence or seed germination were assessed at 12 days after treatments. all biotypes from both species had similar seedling emergence in relation to soil depth. increasing soil depth reduced seedling emergence. sandy substrate facilitated seed germination at 0.5 and 1.0 cm depth. the species are positive photoblastic. optimum temperature for seed germination for both species was 20 oc, but c. canadensis germinates better at temperatures below the optimum and c. bonariensis germinates better at temperatures above the optimum.
Seletividade dos herbicidas S-metolachlor e alachlor para o feij?o-carioca
Lamego, F.P;Basso, C.J;Vidal, R.A;Trezzi, M.M;Santi, A.L;Ruchel, Q;Kaspary, T.E;Gallon, M;
Planta Daninha , 2011, DOI: 10.1590/S0100-83582011000400018
Abstract: the common bean is a culture with a short vegetative cycle, highly susceptible to weed interference. the objective of this work was to evaluate the efficacy of herbicides applied in pre emergence for digitaria sanguinalis control in "carioca" bean crop, as well as to determine their selectivity to the crop. the treatments evaluated were: s-metolachlor (960; 1,440 and 1,920 g ha-1), alachlor (1,440; 1,920 and 2,400 g ha-1), and two untreated checks without herbicide application (with and without hoeing control). visual evaluations of control for d. sanguinalis and injury to the common bean plants were conducted at 20 and 40 days after emergence (dae). at all the evaluated rates, the herbicides were efficient in d. sanguinalis control. at 40 dae, injury to the common bean was observed in the plots sprayed with s-metolachlor at the highest rates, but without deleterious effect on the crop grain yield. despite being efficient in d. sanguinalis management, alachlor caused phytotoxicity to the "carioca" common bean, reducing crop yield up to 47%.
Teste rápido de imers?o foliar de Euphorbia heterophylla para confirma??o de resistência a herbicidas inibidores da Protox e da ALS
Trezzi, M.M;Xavier, E;Vidal, R.A;Portes, E.D.S;Vottri, M;Lamego, F.P;
Planta Daninha , 2011, DOI: 10.1590/S0100-83582011000400021
Abstract: tests to verify resistance (r) vary according to time of execution and degree of complexity, and the efficacy of rapid and simple methods to confirm weed resistance to herbicides must be determined. two experiments were simultaneously carried out in a completely randomized design, under laboratory conditions, by submerging leaves of e. heterophylla susceptible and with multiple resistance to als-and ppo inhibitors in herbicide solutions. the aerial part of the plants was submerged in herbicide solution at different concentrations of imazethapyr, imazapyr, and nicosulfuron (als inhibitors), and fomesafen, lactofen and carfentrazone (ppo inhibitors). s biotype control increased with time and commercial ratings of als and protox inhibitors had an effective control. the r biotype showed different levels of resistance as a function of the herbicide and variable evaluated. the results confirm that leaf immersion technique is adequate to discriminate s biotypes from those with multiple resistance to als and ppo inhibitors. the technique proved to be quick enough for early detection of resistance, allowing the adoption of measures to deal with resistance during the same season.
A solubilidade de fosfatos naturais em solu??o de ácido cítrico a 2%, na propor??o de 1:200
Catani, R.A.;
Anais da Escola Superior de Agricultura Luiz de Queiroz , 1970, DOI: 10.1590/S0071-12761970000100001
Abstract: the solubility of three samples of pure tricalcium phosphate and of one sample of bone meal in 2% citric acid solution, in the proportion of 1:200, is almost total, that is,their content in p2o5. by other side, the rock phosphates present a partial solubility in 200 ml of 2% citric acid. the number of milliequivalents of hydrogen in 200 ml of 2% citric acid solution is almost the doble of the number required for the solubilization of 1 gram of phosphate or calcium fluophosphate. on the basis of the data obtained from this study it is possible to stablish the proportion of 1:200 for the extraction of p2o5 of rock phosphate and to interpret the extracted p2o5 as equivalent to tricalcium phosphate (tfe).
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