Abstract: Background: Eragrostis plana is an invasive plant in native grassland areas associated with degradation of the Pampa biome. Selective control of E. plana is difficult due to its similarity to other grassland species. There is a lack of information about E. plana control using selective herbicide application equipment. Objective: The present study aimed to evaluate the efficacy of a pressurize rope wick applicator for controlling the invasive plant E. plana as function of different salts of glyphosate, application volumes, and year seasons. Methods: The studies were carried out under field conditions and repeated. The first study evaluated glyphosate salts of isopropylamine, dimethylamine, monoammonium, diammonium, and potassium at doses of 720 and 1440 g ha-1 and clethodim at 60 and 120 g ha-1. The second study assessed application volumes of 8, 24, 40, and 56 L ha-1 using isopropylamine and potassium salts of glyphosate. Results: Glyphosate applied in summer was more effective at controlling E. plana, with less regrowth than glyphosate application in winter. The glyphosate diammonium was more effective at controlling E. plana than isopropylamine, dimethylamine, monoammonium, or potassium salt formulations at 1440 g ha-1. Application volume of glyphosate between 8 and 40 L ha-1 provided similar control of E. plana and pasture selectivity. Conclusions: Glyphosate applied with a rope wick selective applicator was effective in controlling E. plana clumps and was selective to grassland. The control efficacy varied as a function of glyphosate salts and year season, but not due to application volume of 8 and 40 L ha-1.

RESUMO A buva (Conyza bonariensis L.) é umas das principais plantas daninhas dos sistemas de cultivos conservacionistas, especialmente por sua evolução à resistência ao herbicida glyphosate. Os objetivos deste trabalho foram verificar a resposta de Conyza bonariensis suscetível (S) e resistente (R) ao glyphosate em diferentes estádios a herbicidas alternativos e avaliar o potencial fisiológico de sementes destes biótipos. Dois estudos foram realizados e repetidos, sendo o primeiro em casa de vegetação em esquema fatorial 2x3x10, sendo A: biótipos de buva (S e R); B: estádios de desenvolvimento (I (1-2 folhas), II (5-6 folhas) e III (30-35 folhas)) e C: herbicidas (glyphosate, chlorimuron-etílico, metsulfuron-methyl, diclosulam, amônio-glufosinato, paraquat, paraquat+diuron, diquat, 2,4-D além de testemunha não aplicada).O segundo estudo foi desenvolvido em laboratório, realizando-se avaliações do potencial fisiológico das sementes, a partir do por peso de mil sementes (PMS), germinação (G), primeira contagem da germinação (PG), índice de velocidade de germinação (IVG) e emergência (IVE), comprimento da parte aérea (CPA), raiz (CR) e total (CT), matéria seca da parte aérea (MSPA), raízes (MSR) e total (MST), testes de frio e envelhecimento acelerado. O biótipo CR foi eficientemente controlado pelos herbicidas alternativos ao glyphosate, utilizados até o estádio de 6 folhas. As sementes do biótipo CR apresentaram desempenho fisiológico superior em todas as variáveis analisadas, com maior tolerância a condições adversas em seu estabelecimento. O manejo de buva resistente a glyphosate demanda a utilização de estratégias que visem evitar a produção de novas sementes.

ABSTRACT Hairy fleabane (Conyza bonariensis L.) is a major weed of the conventional crop systems. Therefore, the objectives of the present study were to assess the responses of glyphosate-susceptible (S) and -resistant (R) C. bonariensis at various developmental stages and evaluate the physiological potential of seeds to propose alternative herbicides for the control of this weed. Two experiments were performed in replicates. The first experiment was performed in a greenhouse, arranged in a 2 x 3 x 10 factorial design. Specifically, two hairy fleabane biotypes (S and R) at different developmental stages (I, II, and III) were subjected to various treatments (glyphosate, chlorimuron-ethyl, metsulfuron-methyl, diclosulam, ammonium glufosinate, paraquat, paraquat+diuron, diquat, 2,4-D, and control). Percentage control was evaluated at 7, 14, 21, and 28 days after the application of the treatments (DAT), and shoot dry mass (SDM) was measured at 28 DAT. The second experiment was performed in a laboratory to evaluate the physiological potential of seeds based on the weight of 1000 seeds (TSW); shoot length (SL), radicle length (RL), total length (TL), fresh seedling mass (FSM), dry seedling mass (DSM), accelerated aging (AA) and cold test (CT), and germination (G) in response to cold and accelerated aging. The alternative herbicides tested effectively controlled biotype R up to the stage -I. Seeds of biotype R showed higher physiological potential in terms of all analyzed variables and exhibited greater tolerance to adverse conditions during seedling establishment. Therefore, strategies for the management of glyphosate-resistant hairy fleabane should aim at preventing new seed production.

ABSTRACT Chlorophylls and carotenoids are the main photosynthetic pigments in plants, and photosynthetic potential can be used to determine the nitrogen fixation or cycling capacity of cover crops. Therefore, this study quantified and compared the content of photosynthetic pigments in Raphanus sativus and Vicia sativa by using two different methods, namely the extraction method and measurements with a portable chlorophyll meter, and determined whether the results of these two methods showed a significant correlation. Photosynthetic pigments were measured, using both methods, in a greenhouse and laboratory, at four developmental stages: the vegetative stages I (30 days after sowing [DAS]), II (60DAS), and III (90DAS), and the reproductive stage (150DAS). The determination of the photosynthetic pigment content in R. sativus and V. sativa, obtained from the extraction method and chlorophyll index, revealed significant differences depending on the developmental stage in both species. Furthermore, the contents of chlorophyll a, chlorophyll b, and carotenoids determined using the extraction method showed high coefficients of correlation with the total chlorophyll index determined using the portable chlorophyll meter. Therefore, the portable chlorophyll meter can be used for the accurate evaluation of the photosynthetic potential of Raphanus sativus and Vicia sativa, which also saves time and reagents.

ABSTRACT. The flooded environment brings about injuries to soybeans that vary depending on the adaptation ability of the genotype. Oxygen deprivation promotes the induction of the expression of genes related to glycolysis and fermentation pathways to maintain energy metabolism and, in addition to reducing-power consuming processes, act in the formation of adaptive structures and the maintenance of the redox status of the plant. The aim of this work was to evaluate the relative expression of genes related to soil flooding response in two contrasting soybean cultivars. Soybean plants of the sensitive (BRS 154) and tolerant (I27) cultivars at the V1 development stage were submitted to the flooding and control conditions (without flooding) for 0, 24, 48, and 96 hours. The relative expression of genes associated with flooding, including enolase (ENO), alcohol dehydrogenase 1 (ADH1), alanine aminotransferase 2 (ALAT2), hemoglobin 1 (GLB1), LOB41 domain-containing protein (LBD41), xyloglucan endotransglycosylase (XETP) and ascorbate peroxidase (APX2), was evaluated by means of RT-qPCR. The relative expression, in general, increased with flooding, especially in the root tissue. Cultivar I27 responded positively as observed by the expression of the maintenance genes of energy metabolism, structural changes and detoxification, suggesting the presence of three tolerance mechanisms in the flooding response.

ABSTRACT Glyphosate is the herbicide most used worldwide. In cropping systems that rely on repeated applications of glyphosate or cultivate genetically modified soyabean crop, there are numerous cases of glyphosate resistant weeds, including Conyza bonariensis. Differences among competitive ability of Conyza spp. have been found. However, little information is available on the fitness costs related to glyphosate resistance in Conyza bonariensis. We evaluated growth, phenology, and seed viability of glyphosate-resistant (GR) and glyphosate-susceptible (GS) Conyza bonariensis from Brazil, in 2012 (fall/winter) and 2013 (spring/summer). When grown alone, in pots, C. bonariensis GR biotype developed more rapidly than the GS biotype, as evidenced by their earlier bolting, flowering, and seed set. In 2012, GR biotype showed 221.9 cm of plant height compared to 181.1 cm from GS, at the flowering time. In both years, the seed production per plant was superior for GR biotype, showing germination higher than 80% against 66.5% from the GS biotype. Thus, C. bonariensis GR biotype confirmed no fitness penalty also showing characteristics that allow us to infer in superior competitive with the absence of the herbicide. It is important to point out that the biotypes evaluated here have different genetic background and the differences between them may not be fully attributed to the resistance to glyphosate. However, the GR biotype can persist in the environment and outcompete with GS biotypes regardless of further glyphosate selection of pressure.

RESUMO O estabelecimento de culturas comerciais em sucessão a coberturas de inverno, com presença de densa camada de palha, proporciona significativa supressão de plantas daninhas. O objetivo deste trabalho foi avaliar o potencial supressor de coberturas de inverno sobre a incidência inicial de plantas daninhas na cultura do milho e seu efeito na produtividade da cultura semeada em sucessão. Um experimento foi conduzido no ano agrícola de 2012/2013, em área experimental da UFSM, Campus de Frederico Westphalen RS. Foram utilizadas quatro diferentes espécies de cobertura de inverno (aveia-preta, azevém, ervilhaca e nabo) semeadas em faixas, além da testemunha mantida em pousio. No pleno florescimento das coberturas foi realizada a quantificação da massa seca e a dessecação das mesmas. O milho foi semeado em sistema de plantio direto em sucessão às coberturas. Aos 15 dias após a emergência do milho foi avaliada a incidência e a massa seca de parte aérea das plantas daninhas presentes (0,25 m²). As principais espécies daninhas presentes na área foram: corriola (Ipomoea grandifolia), leiteiro (Euphorbia heterophylla), milhã (Digitaria sanguinalis), tiririca (Cyperus rotundus). De forma geral, a ervilhaca e o azevém foram as coberturas de inverno com maior capacidade supressora sobre as plantas daninhas avaliadas. O melhor desempenho produtivo do milho foi observado sobre a palhada de azévem, inferindo para uma relação de supressão de plantas daninhas e produtividade da cultura.

ABSTRACT The establishment of commercial crops in succession to winter cover crops that leaves a dense straw layer provides significantly suppression of weeds. The objective of this work was to evaluate the suppressive potential of winter cover crops on weed infestation in maize and its effect on the yield of the maize sown in succession. The experiment was conducted in the 2012/2013 crop season, in an area of the UFSM Campus Frederico Westphalen, State of Rio Grande do Sul. Four different species of cover crops (black oat, ryegrass, vetch and forage radish) were seeded and a fallow area was used as control. Evaluations to quantify the dry matter and chemical desiccation were performed at the full flowering period of the cover crops. Maize was sown in no-tillage system, in succession to the cover crops. The incidence and shoot dry matter of weeds (g 0.25 m-2) was evaluated 15 days after the maize emergence. The main weed species in the area were: morning-glory (Ipomoea grandifolia), wild poinsettia (Euphorbia heterophylla), large crabgrass (Digitaria sanguinalis) and purple nutsedge (Cyperus rotundus). In general, vetch and ryegrass were the winter cover crops that better suppressed the weeds evaluated. The best maize yield was found in the area previously covered with ryegrass, inferring a relation between the cover crop and suppression of weeds and crop yield.

RESUMO A espécie Solanum torvum consegue desenvolver-se em solos com forte carga de nematoides e fungos patogênicos. Atualmente, é muito demandada na agricultura intensiva como porta-enxerto de espécies de Solanaceae, tais como berinjela e tomate. Objetivou-se comparar tratamentos, buscando o melhor método para acelerar a germinação de lotes de sementes de S. torvum. Três lotes de sementes foram submetidos a quatro tratamentos para superação de dormência (água, nitrato de potássio, ácido giberélico e pré-embebição em ácido giberélico). Avaliaram-se a primeira contagem de germinação, porcentagem de germinação, índice de velocidade de germinação, tempo médio de germinação e a velocidade média de germinação. Os tratamentos com ácido giberélico, com pré-embebição ou apenas com o substrato umedecido, apresentaram os melhores índices de velocidade de germinação, tempo médio de germinação e velocidade média de germinação. A porcentagem final de germinação apresentou interação significativa entre tratamentos e lotes de sementes. Portanto, os tratamentos afetam a germinação final de maneira dependente do lote.

ABSTRACT The Solanum torvum species can grow in soils with a heavy load of nematodes and pathogenic fungi. It is currently much in demand in intensive agriculture as a rootstock of Solanaceae species, such as eggplant and tomato. This study aimed at comparing treatments, in order to determine the best method to accelerate the germination of S. torvum seed batches. Three seed batches were submitted to four treatments to overcome dormancy (water, potassium nitrate, gibberellic acid and pre-imbibition in gibberellic acid). The first germination count, germination percentage, germination speed index, mean germination time and mean germination speed were assessed. Treatments with gibberellic acid, with either pre-imbibition or only moistened substrate, exhibited the best germination speed index, mean germination time and mean germination speed. The final germination percentage showed a significant interaction between treatments and seed batches. Therefore, the treatments affect the final germination in a batch-dependent manner.

RESUMO Durante a aplicação de inseticidas, na cultura da soja, forma-se um gradiente vertical de deposição do produto ao longo do dossel, resultando em dificuldades no controle dos percevejos que se encontram nos terços médio e inferior das plantas. Objetivou-se avaliar a sistematicidade do inseticida tiametoxam em diferentes estágios da cultura da soja, utilizando-se o percevejo marrom como bioindicador da ação do inseticida. O estudo combinou locais de aplicação do produto (terço inferior, médio e superior) e de infestação dos percevejos, em cinco fases do estágio fenológico (R2, R3, R4, R5.2 e R6) da cultura da soja. Nos estágios R2 e R5.2, as plantas apresentaram translocação acropetal do produto, sendo o efeito mais pronunciado no estágio R2. Nos estágios R3, R4 e R6, não houve translocação suficiente do produto para o controle dos percevejos. Em todos os estágios, nos tratamentos com exposição direta (mesmo local de infestação e pulverização), houve controle satisfatório dos percevejos.

ABSTRACT During the application of pesticides on soybean fields, a vertical deposition gradient of the product can occur throughout the canopy, resulting in difficulties for controlling stink bugs that are in the middle and lower thirds of plants. This study aimed at evaluating the systemicity of thiamethoxam insecticide in different soybean phenological stages, using brown stink bugs as bioindicators of the pesticide efficacy. The study combined product application sites (lower, middle and upper third) and stink bugs infestation areas at five soybean phenological stages (R2, R3, R4, R5.2 and R6). For the R2 and R5.2 stages, plants presented acropetal translocation of the product, being the effect more evident in the R2 stage. For the R3, R4 and R6 stages, the product translocation was not sufficient for controlling the stink bugs. In all stages, for treatments with direct exposure (same infestation and spraying place), stink bugs were satisfactorily controlled.