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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 × 3 × 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. 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.

Soybean crop productivity is limited by several biotic factors, particularly plant-parasitic nematodes. Several species have been reported to cause crop damage, especially those of the genus Meloidogyne. Therefore, the aim of this study was to evaluate, the reaction of 28 soybean genotypes to Meloidogyne arenaria and M. morocciensis in a greenhouse. The soybean genotypes were the same for experiments with different species of plant-parasitic nematodes and were individually inoculated with 5,000 eggs + second-stage juveniles (J2) of Meloidogyne and kept in a greenhouse. After 60 days of inoculation, the roots of each plant were assessed for the number of galls, final population, and reproduction factor (RF = final population/initial population). The averages of the different variables were then compared to each other by the Scott-Knott cluster analysis at a significance level of 5%. All of the soybean genotypes in the study were susceptible to both nematodes, with RF ranging from 3.5 to 24.1 for M. arenaria and 5.3 to 37.5 for M. morocciensis.

Flooding is an important strategy for weed control in paddy rice fields. However, terrestrial weeds had evolved mechanisms of tolerance to flooding, resulting in new ‘snorkeling’ ecotypes. The aim of this review is to discuss the mechanisms of flooding tolerance in cultivated and weedy rice at different plant stages and the putative utility of this trait for weed management. Knowledge about flooding tolerance is derived primarily from crop models, mainly rice. The rice model informs us about the possible flooding tolerance mechanisms in weedy rice, Echinochloa species, and other weeds. During germination, the gene related to carbohydrate mobilization and energy intake (RAmy3D), and genes involved in metabolism maintenance under anoxia (ADH, PDC, and OsB12D1) are the most important for flooding tolerance. Flooding tolerance during emergence involved responses promoted by ethylene and induction of RAmy3D, ADH, PDC, and OsB12D1. Plant species tolerant to complete submersion also employ escape strategies or the ability to become quiescent during the submergence period. In weedy rice, the expression of PDC1, SUS3, and SUB1 genes is not directly related to flooding tolerance, contrary to what was learned in cultivated rice. Mitigation of flooding tolerance in weeds could be achieved with biotechnological approaches and genetic manipulation of flood tolerance genes through RNAi and transposons, providing a potential new tool for weed management.

Background: The use of pre-emergent herbicides is an important tool to control weeds, however the tolerance of soybean to these herbicides can vary according to the type of soil. Objective: The aim of this study was to evaluate sulfentrazone and diclosulam soybean selectivity in a sandy soil, in order to establish these herbicides as supporting tools in weed control. Methods: The treatments consisted of six doses of sulfentrazone (150 to 400 g ha-1) and diclosulam (25.2 to 75.6 g ha-1), and an untreated control. A field study was repeated in two growing seasons (2013/14 and 2014/15) in a sandy soil. Results: The occurrence of injury depended on the growing season. The first season presented lower rainfall rates during the crop cycle. The recommended dose of sulfentrazone (200 g ha-1) caused 26% and 10% of plant injury at 15 days after the treatment for the first and second season, respectively. For diclosulam, the recommended dose of 35.3 g ha-1 caused 20% and 8% of plant injury, respectively, for the first and second season. However, at the recommended doses, only for diclosulam and in the rainy season there was a reduction in soybean productivity. Conclusions: The herbicide sulfentrazone, although causing visual soybean plant injury, present satisfactory selectivity at recommended doses and can be used as an important tool on weed control on sandy soils. Similar response was observed for diclosulam in 2013/14. However, in a rainfall season diclosulam impacted on soybean yield at the recommended dose for sandy soils, with selectivity depending of the growth season.

Weeds can be hosts of root-lesion nematode (Pratylenchus spp.), maintaining or increasing their population in the soil. The objective of this study was to evaluate the reaction of 25 weeds species to the nematode Pratylenchus zeae. The weed plants were individually inoculated with 1,000 individuals of P. zeae and maintained in a greenhouse for 90 days. After this period, eggs and nematodes were extracted, quantified, and the reproduction factor (RF = final population/initial population) was calculated. All tested weeds were susceptible (RF>1) to P. zeae, and the species Brachiaria decumbens, Rhynchelytrum repens, Digitaria insularis, D. horizontalis, B. brizantha were the most susceptible to this parasite. RESUMO As plantas daninhas podem ser hospedeiras de nematoides das lesões (Pratylenchus spp.), mantendo ou elevando sua população no solo. O objetivo deste trabalho foi avaliar a reação de 25 espécies de plantas daninhas a Pratylenchus zeae. As plantas daninhas foram individualmente inoculadas com 1.000 espécimes de P. zeae e mantidas em casa de vegetação por 90 dias. Após esse período, os ovos e nematoides foram extraídos e quantificados, sendo calculado o fator de reprodução (FR = população final/população inicial). Todas as plantas daninhas avaliadas comportaram-se como suscetíveis (FR>1) para P. zeae, sendo as espécies Brachiaria decumbens, Rhynchelytrum repens, Digitaria insularis, D. horizontalis e B. brizantha as mais suscetíveis a esse parasita.

Chlorophylls and carotenoids are the main photosynthetic pigment in plants. In the weeds, the greatest amount of photosynthetic pigments can result in high competitiveness of the species. The aim of this study was to quantify the content of photosynthetic pigments in biotypes of fleabane (Conyza bonariensis) susceptible and resistant to glyphosate, by two different methods, as well as a correlation between chlorophyll content obtained by portable and classical methodology (extractable chlorophyll). An experiment was conducted in greenhouse and laboratory, 2 x 5 factorial scheme, where factor A was equivalent to biotypes of fleabane (resistant and susceptible to glyphosate) and factor B to developmental stages plants (rosette vegetative I, II and III and reproduction). At all stages of development, fleabane plants were evaluated with the portable determiner (chlorophyll content) and then the same leaves were subjected to classical methodology laboratory (extractable pigments). The resistant biotype of fleabane showed higher contents of chlorophyll a, b, and total carotenoids, inferring a greater competitive potential regarding the susceptible population to the herbicide. The portable determiner of chlorophyll showed high correlation with the classical method of determination of photosynthetic pigments, and can thus be used to accurately assess this, saving time and reagents. Clorofilas e carotenoides são os principais pigmentos fotossintéticos em plantas. Nas plantas daninhas, a maior quantidade de pigmentos fotossintéticos pode resultar em elevada competividade da espécie. O objetivo deste trabalho foi quantificar o teor de pigmentos fotossintéticos em biótipos de buva (Conyza bonariensis) suscetível e resistente ao herbicida glyphosate, por dois diferentes métodos, bem como estabelecer uma correlação entre o índice de clorofila obtido pelo equipamento portátil e a metodologia clássica (clorofila extraível). Um experimento foi conduzido em casa de vegetação e laboratório, em esquema fatorial 2 x 5, em que o fator A equivaleu aos biótipos de buva (resistente e suscetível a glyphosate) e o fator B, a estádios de desenvolvimento das plantas (roseta, vegetativo I, II e III, e reprodutivo). Em todos os estádios de desenvolvimento, as plantas de buva foram avaliadas com o determinador portatil (índice de clorofila); em seguida, as mesmas folhas foram submetidas à metodologia clássica de laboratório (pigmentos extraíveis). O biótipo de buva resistente apresentou maiores teores de clorofila a, b, total e carotenoides, demonstrando maior potencial competitivo frente ao biótipo suscetível ao herbicida glyphosate. O determinador portátil de clorofila apresentou alta correlação com o método clássico de determinação de pigmentos fotossintéticos, podendo, assim, ser usado com precisão na avaliação destes, proporcionando economia de tempo e reagentes.

A antecipação da colheita da soja é possível com uso da prática de dessecação pré-colheita, a qual reduz o tempo de permanência das sementes no campo, após a maturação fisiológica. O objetivo deste trabalho foi avaliar o efeito da época de aplicação do herbicida paraquat, como dessecante na pré-colheita da soja, sobre a produtividade e qualidade fisiológica de sementes. O trabalho constou de duas etapas: um experimento em campo, conduzido no município de Jaboticaba-RS, safra 2010/2011, e uma análise da qualidade fisiológica das sementes. Os tratamentos consistiram de três épocas de aplicação do paraquat (240 g i.a. ha‑1), R6, R7.1 e R7.3, bem como de um tratamento testemunha (sem dessecação). Foram avaliados a produtividade de grãos e os componentes da produtividade. A análise da qualidade das sementes foi conduzida no Laboratório de Produção e Tecnologia de Sementes da UFSM, Campus de Frederico Westphalen, RS, onde se realizaram os seguintes testes: germinação; primeira contagem de germinação, comprimento de parte aérea e radicular, matéria seca de plântulas, envelhecimento acelerado, condutividade elétrica, emergência em campo e índice de velocidade de emergência. A aplicação de paraquat como dessecante na pré‑colheita da soja, nos estádios R6 e R7.1, provoca queda acentuada na produtividade da cultura. A dessecação sem perda de potencial produtivo da soja só é viável a partir do estádio R7.3. Sementes oriundas de plantas com dessecação nos estádios R6 e R7.1 apresentam percentual superior e maior velocidade de germinação. Entretanto, sementes de plantas com dessecação no estádio R6 possuem menor vigor de plântulas.

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 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.

Understanding spatial distribution of weeds in the crop enables to perform localized herbicide applications, increasing the technical and economic efficiency of operations and reducing environmental impacts. This work aimed to characterize the spatial and phytosociological variability of weeds occurring in soybean commercial field. It was conducted in an agricultural area located at the municipality of Boa Vista das Missões - RS, during the 2010/2011 harvest season. The area, that had been managed under no-tillage with soybean monoculture (summer) for five years, was divided in regular squares of 50 x 50 m (0.25 ha), totalizing 356 points. For species identification, 0.5 x 0.5 m sample squares were used. During the survey, 1,739 individuals were identified, distributed in 19 species of 13 families. The weed species Cardiospermum halicacabum, Digitaria horizontalis, Urochloa plantaginea and Raphanus raphanistrum showed the highest population variation in the area; however, only C. halicacabum, U. plantaginea and R. raphanistrum stood out based on the Importance Index Value (IVI). Localized management strategies considering the spatial variability of weed species placed in the Magnoliopsidas and Liliopsidas group show a high potential for use in soybean crop. The results show that the sampling method through regular grid was capable of characterizing the occurrence, population density and spatial variability of weed species in soybean crop.

This study aimed to evaluate the yield and seed quality of wheat, cultivar ‘Quartzo’, harvested after desiccation with two desiccants (glyphosate and paraquat) at two reproductive stages (11.2 and 11.3). The study used a randomized block experimental design in a 3 x 2 factorial arrangement (two desiccants and a control) and two growth stages of wheat, with four replications. The following were assessed: seed yield, thousand seed weight and seed quality (germination, first germination count, root and shoot weight, seedling dry and fresh weight, accelerated aging, electrical conductivity, cold germination, potassium leaching). Based on the results, it can be concluded that the use of desiccants on wheat at the two stages of development have not affected yield, but they have negatively influenced physiological seed quality. Generally, the herbicide glyphosate showed the lowest phytotoxic effect on seeds, and desiccant application at stage 11.2 resulted in higher physiological seed quality compared with application at stage 11.3.

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. MANEJO DE BUVA RESISTENTE AO GLYPHOSATE E CONSEQUÊNCIAS DO POTENCIAL FISIOLÓGICO DE SEMENTES À RESISTÊNCIA 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. Made available in DSpace on 2021-09-16T02:14:35Z (GMT). No. of bitstreams: 1 KASPARY-et-al-2021.pdf: 7429836 bytes, checksum: 86425c9418070e579dcfb61230eaa4f0 (MD5) Previous issue date: 2021