Diecson Ruy Orsolin da Silva

Glyphosate-resistant hairy fleabane competition in RR® soybean

Weed competition in the soybean causes changes in morphological and physiological characteristics that reduce the competitive ability of the crop. The objective of this study was to determine the control periods and coexistence of glyphosate-resistant hairy fleabane and its interference in morphological and photosynthetic variables and RR soybean yield. A field experiment was conducted during the 2011/2012 growing season, the treatments consisted of weed interference and weed free periods of the glyphosate-resistant hairy fleabane with soybean (BRS Estância RR). The periods were 0, 7, 14, 21, 28, 35, 42 and 154 days after the soybean emergence. The results sugested no differences between the control periods for the variables evaluated. The increase interference period of the weed reduced growth, development and the photosynthetic variables in the soybean. There are positive correlations between morphological and photosynthetic variables of soybean during the weed interference. The period before the glyphosate-resistant hairy fleabane interference in the soybean crop is 24 days for plants established before the crop sowing.

Competição de trigo com azevém em função de épocas de aplicação e doses de nitrogênio

Wheat productivity potential is limited by competition with weeds, especially considering light, water, and nutrient resources. The objective of this work was to evaluate morphological variables and productivity components in wheat in competition with ryegrass, considering application times and N doses. The first factor evaluated was the competition condition (absence and presence of ryegrass); the second factor was N application times (100% applied at the beginning of tillering; 50% applied at the beginning of tillering and 50% at the beginning of spike differentiation [BSD]; and 100% at BSD); and the third factor was N doses (0, 40, 80, 120 and 160 kg ha-1). The variables evaluated were: leaf area (LA), aerial part dry mass (APDM), number of tillers ( NT), number or stems (NS), N content in the culture(CN), number of grain per spikelet (NGPS), spike grain number (SGN), number of grains per spike (NGS), biological productivity (BP), average weight of 1000 grains (AWG) and grain productivity (P). The results showed that ryegrass competes with wheat for nitrogen reducing FA, APDM, NT, NT, NS, NGPS, CEGN, BP, AWG and P of the culture. N application at the beginning of tillering or fractionated, at the two highest doses, increases FA and MSPA. N dose increase accelerates CN in wheat culture, independent of the presence or absence of the competitor. N application in BSD or increased N dose increase NSPS and SGN.

Pig slurry as a nutrient source in wheat/corn succession

Wheat and corn are important grains in the agricultural scenario of Brazil, and demand adequate supply of nutrients, particularly nitrogen, in crop succession. The use of pig slurry (PS) as a full and/or partial alternative to mineral fertilization in crop areas has been identified as an important alternative for the disposal of this waste. Therefore, the objective of this study was to evaluate the utilization of PS as fertilizer in wheat/corn succession under some plant parameters and grain yield. The experiment was conducted under field in randomized block design with four replications and five treatments, three with PS (40, 80, 160 m³ ha-1) and two controls (no fertilization and mineral NPK fertilization), which were applied manually in the soil shortly after sowing the crops. The application of PS proved to be a significant source of nutrients in wheat/corn succession. In comparison to NPK fertilization, this increase was only of 5.4% and 4.7% for wheat and corn, respectively. PS is an efficient alternative and it can be used as a source of these nutrients in wheat/corn succession, and the use of 80 m3ha-1 provides satisfactory results for all evaluated variables.

Herbicidas alternativos para o controle de Conyza sumatrensis (Retz.) E. H. Walker resistentes aos inibidores da ALS e EPSPs

Horseweed (Conyza sumatrensis), the major weed already identified in southern Brazil come presenting unsatisfactory control in response to application of herbicide chlorimuron-ethyl and glyphosate. In this context, the aim of this study was evaluating alternative herbicides for control of biotypes of C. sumatrensis with low-level resistance to the herbicide chlorimuron-ethyl and glyphosate-resistant. The experiment was carried out in a greenhouse, in a period during the interval April to August 2012, in Passo Fundo / RS. The experimental design was the completely randomized with four replications, with 15 herbicide treatments, plus an untreated control. The variables evaluated were percent control at 14, 21 and 28 days after treatment (DAT) and dry weight of shoot at 28 DAT. The results showed that the biotypes were 100% controlled at 28 DAT for alternative treatments of paraquat + diuron, ammonium glufosinate, glyphosate + 2,4-D, glyphosate and ammonium glufosinate; 2,4-D; tembotrione and tembotrione + atrazine. The biotype 17 showed less sensitivity to ALS-inhibiting herbicides, and biotypes 05, 17 and 20 were not controlled by glyphosate.

MOLECULAR CHARACTERIZATION OF HAIRY FLEABANE USING RAPD

Com a evolucao do aparecimento de casos de buva resistente ao glyphosate, o conhecimento da diversidade genetica e importante para auxiliar no manejo dessa planta daninha. Assim, o objetivo deste estudo foi caracterizar a diversidade genetica de plantas de Conyza spp. resistentes ao glyphosate ocorrentes no Rio Grande do Sul. Foram coletadas sementes de biotipos de buva em areas de cultivo de soja geneticamente modificada resistente ao glyphosate, das quais foi extraido DNA das folhas para analise de diversidade genetica, utilizando-se a tecnica de RAPD. O DNA foi usado na reacao de polimerase em cadeia, e os fragmentos de DNA foram avaliados quanto ao polimorfismo das bandas em eletroforese. Os biotipos foram identificados como Conyza bonariensis variedades bonariensis e microcephala. Na analise molecular dos 25 primers testados, oito apresentaram polimorfismos reprodutiveis e de alta intensidade para a separacao dos biotipos. A analise de agrupamento revelou cinco grupos, os quais apresentaram similaridade genetica de 53%. Os resultados indicam que todos os biotipos identificados sao da mesma especie, porem apresentam variedade distinta. A tecnica de RAPD apresenta-se como importante ferramenta para caracterizacao de especies de Conyza.