FITORREMEDIAÇÃO: PLANTAS COMO AGENTES DE DESPOLUIÇÃO?

Esta revisão teve como objetivo abordar aspectos da fitorremediação e sua aplicação para a descontaminação de áreas poluídas, decorrentes de atividades humanas. Foram discutidos os métodos de fitorremediação, os processos fisiológicos envolvidos, as propriedades das plantas utilizadas e sua relação com a biotecnologia, bem como vantagens e desvantagens dessa tecnologia. Atividades realizadas pelo ser humano como a industrialização e o uso de químicos na agricultura geram poluentes e a remoção dos compostos potencialmente tóxicos formados torna-se complexa, uma vez que existem diferentes classes e tipos de químicos. Outro aspecto que dificulta a recuperação de áreas contaminadas é o custo oneroso de métodos tradicionalmente utilizados para remoção dos poluentes. Deste modo, a fitorremediação vem despertando interesse mundial e apresenta potencial para uso no Brasil. Pesquisas científicas têm selecionado diversas espécies vegetais com potencial para limpeza de áreas contaminadas e a biotecnologia tem possibilitado a adequação da habilidade descontaminante de outras espécies

Fitness of Echinochloa crusgalli var. mitis biotypes susceptible and resistant to imazapyr + imazapic herbicide

The continuous use of herbicides with the same mechanism of action has caused the selection of resistant weed biotype that may present differences in fitness when compared with susceptible biotype. The objective of the present study was to identify and distinguish the fitness of barnyardgrass biotypes resistant and susceptible to imazapyr + imazapic herbicide under controlled and noncompetitive conditions. For that, there were used barnyardgrass biotype susceptible (ECH1 and ECH38) and resistant (ECH14 and ECH44) to ALS inhibitors, collected at Pelotas/RS and Rio Grande/RS cities, respectively, in experiment installed in a greenhouse in a completely randomized experimental design during the months from October to December 2015. The biotype were evaluated during the period of 15 to 120 days after the emergence related to plant height, foliar area, shoot dry matter mass and root dry matter mass. The results showed insignificant differences between the biotypes during the development of the plants. The susceptible biotype ECH44 showed a higher number of panicles per plant and seeds along with the resistant ECH1. There is variability among Echinochloa crusgalli var. mitis biotypes resistant and susceptible to ALS inhibitors, indicating an absence in fitness penalty caused by resistance when cultivated without the selection of pressure (herbicide).The continuous use of herbicides with the same mechanism of action has caused the selection of resistant weed biotype that may present differences in fitness when compared with susceptible biotype. The objective of the present study was to identify and distinguish the fitness of barnyardgrass biotypes resistant and susceptible to imazapyr + imazapic herbicide under controlled and noncompetitive conditions. For that, there were used barnyardgrass biotype susceptible (ECH1 and ECH38) and resistant (ECH14 and ECH44) to ALS inhibitors, collected at Pelotas/RS and Rio Grande/RS cities, respectively, in experiment installed in a greenhouse in a completely randomized experimental design during the months from October to December 2015. The biotype were evaluated during the period of 15 to 120 days after the emergence related to plant height, foliar area, shoot dry matter mass and root dry matter mass. The results showed insignificant differences between the biotypes during the development of the plants. The susceptible biotype ECH44 showed a higher number of panicles per plant and seeds along with the resistant ECH1. There is variability among Echinochloa crusgalli var. mitis biotypes resistant and susceptible to ALS inhibitors, indicating an absence in fitness penalty caused by resistance when cultivated without the selection of pressure (herbicide)

OTIMIZAÇÃO DO NÚMERO DE PRIMERS EMPREGADOS EM RAPD PARA DETECTAR VARIABILIDADE GENÉTICA ENTRE ACESSOS DE PICÃO-PRETO

Molecular markers such as RAPD (Random Amplified Polymorphic DNA) are among the most widely used because they are easy to apply, quick and with low cost. With this marker it is possible to evaluate the structure and the genetic diversity in weed and crop populations. The objective of this work was to evaluate the viability of primer number otimization of RAPD molecular marker to know the genetic similarity of target populations. The data bank of two different experiments conducted with hairy beggarticks (Bidens pilosa L.) acesses, at Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, RS, were evaluated on the effects of the primer numbers on the genetic variability. It was possible to otimize the primer number used by RAPD marker. When few primers promoted good band formation in each population, large number of prime will be necessary for the adequate estimative of genetic variability.Marcadores moleculares do tipo RAPD (polimorfismo de DNA amplificado ao acaso) estão entre os mais utilizados devido a sua facilidade de uso, rapidez e baixo custo. Através deste tipo de marcador é possível avaliar a estrutura e diversidade genética em populações naturais (plantas daninhas) e melhoradas. O objetivo deste trabalho foi avaliar a viabilidade da redução no número de primers utilizados em marcador molecular RAPD para conhecimento da variabilidade genética em populações de plantas daninhas. O banco de dados de dois trabalhos diferentes com acessos de picão-preto (Bidens pilosa L.), conduzidos na Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, foram avaliados quanto ao número de primers e efeito na variabilidade genética. Foi possível otimizar o número de primers utilizados por marcador RAPD. Quando poucos primers promovem boa formação de bandas em cada população, maior número de primers serão necessários para adequada estimativa da variabilidade genética

HERBICIDE RESISTANT WEED MANAGEMENT USING SENSITIVITY ANALYSIS OF THE WEED POPULATION GROWTH CURVE

Strategies to prevent herbicide weed resistance are rarely practiced by farmers. As a consequence, herbicide resistant weed biotypes (HRWB) have been increasing worldwide in the past decades. This paper aims to analyze the weed population growth curve and to propose a strategic plan for prevention and management of HRWB. The existing weed control methods are organized considering the sensitivity analysis of the population growth at each phase of the logistic growth curve. This analysis indicates that tactics directed to reduce the population growth rate are most appropriate for HRWB management, mainly at the initial phase of the resistant weed population growth. This epidemiological approach provides evidence to the importance of early detection and management of HRWB

Floristic composition of weeds in different winter and summer covers

The usage of cover crops is an adopted cultural measure that shows positive effects when associated with the no-till system and weed management. During the cycle of the plants there might be competition within them for water, solar radiation and nutrients and effects of allelopathic substances released by leaching, volatilization and/or root exudation in the environment might also coexist. The study aimed to quantify the floristic composition of weed species in an cultivated area with cover crops during winter and summer, for two years, 2011/12 and 2012/13, in an experimental area of UFSM, Campus of Frederico Westphalen – RS state, Brazil. The treatments consisted of Italian ryegrass, wild radish, black oat, vetch, wheat and uncultivated, in winter, and, sorghum, sunflower, black velvet bean, dwarf velvet bean, gray velvet bean and green velvet bean in the summer. In the first year of the experiment, a diversity of weeds in winter was observed, especially occuring Stellaria media and Bowlesia incana. In summer, the weeds of higher importance were Ipomoea spp. and Bidens spp., both of utter importance in agricultural systems. Winter cover crops of wild radish and Italian ryegrass and summer cover crops of sorghum and sunflower provided a lower weed infestationThe usage of cover crops is an adopted cultural measure that shows positive effects when associated with the no-till system and weed management. During the cycle of the plants there might be competition within them for water, solar radiation and nutrients and effects of allelopathic substances released by leaching, volatilization and/or root exudation in the environment might also coexist. The study aimed to quantify the floristic composition of weed species in an cultivated area with cover crops during winter and summer, for two years, 2011/12 and 2012/13, in an experimental area of UFSM, Campus of Frederico Westphalen – RS state, Brazil. The treatments consisted of Italian ryegrass, wild radish, black oat, vetch, wheat and uncultivated, in winter, and, sorghum, sunflower, black velvet bean, dwarf velvet bean, gray velvet bean and green velvet bean in the summer. In the first year of the experiment, a diversity of weeds in winter was observed, especially occuring Stellaria media and Bowlesia incana. In summer, the weeds of higher importance were Ipomoea spp. and Bidens spp., both of utter importance in agricultural systems. Winter cover crops of wild radish and Italian ryegrass and summer cover crops of sorghum and sunflower provided a lower weed infestatio

Interference of volunteer corn on soybean cultivars growth and yield

Spontaneous corn plants in soybean crop are considered weeds because they compete for the same environmental resources. The objective of this study was to evaluate the competitive ability of soybean cultivars when in coexistence with spontaneous corn plants. A field experiment was conducted in CCGLTEC, Cruz Alta/RS, in 2014/15, in a split-plot design, with the main plot being composed of four different cultivars (CD 2694, BMX 7166, TEC 5718, TEC 6029) and the subplots of interference conditions (without the presence of corn volunteer plants, in the presence of corn until the V3, V6, V9 stages, or for the entire soybean cycle. Leaf area, shoot dry mass, plant height, chlorophyll index, and development stage were determined at 15, 30, and 49 DAE; we also determined apparent biological productivity, apparent harvest index, and components of productivity and grain yield. The cultivars showed losses in leaf area and shoot dry mass when in coexistence with corn (8 plants m-2) in the three periods evaluated. All cultivars showed losses in apparent biological productivity, apparent harvest index, and final grain yield when growing under competition throughout the cycle. Cultivars with a medium/long growth cycle, such as CD 2694 (maturity groups (GM): 6.9) and BMX 7166 (GM: 6.6), show a higher competitive ability up to V9 stage in contrast to cultivars with a short cycle, such as TEC 5718 (GM: 5.9) and TEC 6029 (GM: 5.7).Spontaneous corn plants in soybean crop are considered weeds because they compete for the same environmental resources. The objective of this study was to evaluate the competitive ability of soybean cultivars when in coexistence with spontaneous corn plants. A field experiment was conducted in CCGLTEC, Cruz Alta/RS, in 2014/15, in a split-plot design, with the main plot being composed of four different cultivars (CD 2694, BMX 7166, TEC 5718, TEC 6029) and the subplots of interference conditions (without the presence of corn volunteer plants, in the presence of corn until the V3, V6, V9 stages, or for the entire soybean cycle. Leaf area, shoot dry mass, plant height, chlorophyll index, and development stage were determined at 15, 30, and 49 DAE; we also determined apparent biological productivity, apparent harvest index, and components of productivity and grain yield. The cultivars showed losses in leaf area and shoot dry mass when in coexistence with corn (8 plants m-2) in the three periods evaluated. All cultivars showed losses in apparent biological productivity, apparent harvest index, and final grain yield when growing under competition throughout the cycle. Cultivars with a medium/long growth cycle, such as CD 2694 (maturity groups (GM): 6.9) and BMX 7166 (GM: 6.6), show a higher competitive ability up to V9 stage in contrast to cultivars with a short cycle, such as TEC 5718 (GM: 5.9) and TEC 6029 (GM: 5.7)

RESPOSTA DE CULTIVARES DE SOJA À COMPETIÇÃO COM CULTIVAR SIMULADORA DA INFESTAÇÃO DE PLANTAS CONCORRENTES

Crop yield losses due to competition vary according to weed specie(s) involved and tend to be greater as more alike are the competing species, since these would utilize environmental resources from the same ecological niche. The aim of this work was to estimate the response of soybean cultivars “IAS 5” and “Fepagro RS-10”, when submitted to increasing densities of “Cobb” cultivar , mimicking a broadleaf weed species. To accomplish this, it was carried out one field experiment at Eldorado do Sul – RS. The factors and treatments used were: soybean cultivars (IAS 5 and Fepagro RS-10) and densities of the weed mimicker (Cobb), more checks without its presence. Cobb densities varied from 5 to 36 plants m-2. Data for percent yield losses of the cultivars were adjusted to the non linear retangular hyperbolic regression. The hyperbolic model forecasted at 6,8 and 5,9%, respectively, yield losses suffered by IAS 5 and Fepagro RS-10 cultivars when the weed mimicker genotype aproached zero. It was established that the mutual competition between plants belonging to the same species high, since the presence of a few individuals may greatly reduce soybean grain yield. Soybean cultivar holding low height is affected mostly by competitive stress imposed by concurrent plants presenting high stature.As perdas de produtividade de uma cultura devido à competição variam de acordo com a(s) espécie(s) de planta(s) daninha(s) envolvida(s) e tendem a ser mais elevadas quanto mais semelhantes forem as espécies em competição, pois essas tenderão a usufruir dos recursos do meio a partir do mesmo nicho ecológico. O objetivo deste trabalho foi definir a resposta das cultivares de soja “IAS 5” e “Fepagro RS-10”, quando submetidas ao incremento de densidade da cultivar “Cobb”, simulando espécie daninha dicotiledônea. Para isso, foi conduzido um experimento em campo em Eldorado do Sul - RS. Os fatores e tratamentos utilizados foram: cultivares de soja (IAS 5 e Fepagro RS-10) e densidades da simuladora (Cobb), mais uma testemunha sem sua presença. As densidades de Cobb variaram de 5 a 36 plantas m-2. Os dados de perdas percentuais de produtividade das cultivares foram ajustados ao modelo de regressão não linear da hipérbole retangular. O modelo da hipérbole estimou em 6,8 e 5,9%, respectivamente, as perdas de produtividade sofridas por IAS 5 e Fepagro RS-10 quando a densidade da simuladora de plantas concorrentes se aproxima de zero. Constatou-se que a competição entre plantas de mesma espécie é elevada, uma vez que a presença de poucos indivíduos causa redução importante na produtividade de grãos. Cultivar de soja portadora de baixa estatura é afetada em maior grau pelo estresse competitivo imposto por plantas competidoras de estatura elevada

Avaliação da resistência de Eleusine indica aos herbicidas inibidores da enzima acetil coenzima a carboxilase

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Genetic and geographic distance among beggar-ticks accesses susceptible and resistant to acetolactate sintase herbicide inhibitors

O objetivo deste trabalho foi avaliar o grau de similaridade genética entre acessos de picão-preto, suscetíveis e resistentes aos herbicidas inibidores da enzima acetolactato sintase (ALS) e a relação entre similaridade genética e distância geográfica desses acessos. Sementes dos acessos foram coletadas no Estado do Paraná e cultivadas em casa de vegetação, na Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, em outubro de 2004. Depois da confirmação da resistência ou suscetibilidade dos acessos aos inibidores da enzima ALS, realizou-se a extração de DNA. Por meio da técnica de RAPD, foi possível avaliar a similaridade genética entre os acessos de picão-preto. Na análise conjunta dos acessos, dos 20 iniciadores utilizados, 17 apresentaram-se polimórficos, amplificando um total de 94 bandas. A similaridade genética média foi baixa e equivalente a 37%. A análise de regressão evidenciou que não há relação entre distância genética e geográfica nos acessos de picão-preto avaliados. A baixa similaridade geral entre esses acessos evidencia que a resistência aos herbicidas na região se configura pela seleção de indivíduos resistentes preexistentes na população.The objective of this work was to evaluate the degree of genetic similarity among beggar-ticks accesses, susceptible and resistant to acetolactate sintase (ALS) herbicide inhibitors and the relationship among the genetic similarity and geographic distance of this accesses. Beggar-ticks seeds were sampled at Paraná state and were grown in the greenhouse at Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil, in October 2004. After the confirmation of resistance or susceptibility to ALS inhibitors herbicides, the DNA extraction was performed. Through RAPD analysis, it was possible to evaluate the genetic similarity among beggar-ticks accesses. In the whole analysis of the accesses, from 20 primers assessed, only 17 displayed polymorphism and amplified a total of 94 bands. Average genetic similarity was low (37%). Regression analysis evidenced that there is no relationship between genetic and geographic distance for the beggar-ticks accesses. Low general similarity among accesses evidences that resistance in the region is represented by selection of resistant individuals already existing in the population

ANÁLISE GENÉTICA DE GENÓTIPOS DE Bidens pilosa ATRAVÉS DA TÉCNICA RAPD

Reduced genetic similarity in Bidens pilosa, due to a significant outcross rate favors natural selection of genotypes resistants to herbicides used for control. The objective of present work was to determine the genetic similarity between resistant and susceptible biotypes to herbicides inhibitors of the ALS enzyme. Seeds were collected in Paraná and Rio Grande do Sul States and sowed in the greenhouse at Federal University in Rio Grande do Sul, during 2004. Through the technique of Random Amplified Polymorphic DNA (RAPD), it was possible to evaluate genetic differences among Bidens biotypes. All primers amplified and showed good band reproducibility. The average coefficient of genetic similarity was 43%. The low genetic similarity observed among ALS-resistant and susceptible accesses suggests that the occurrence of resistant genotypes is due to natural selection, acting on a wide spectrum of different genotypes: reduced genetic similarity linked to high genetic variability, caused by significant outcrossing rate.Em Bidens pilosa, elevada variabilidade genética, causada por significativa taxa de polinização cruzada, conduz à reduzida similaridade genética entre genótipos, favorecendo a seleção natural daqueles resistentes aos herbicidas utilizadas no seu controle. O objetivo deste trabalho foi determinar a similaridade genética entre biótipos resistentes e suscetíveis aos herbicidas inibidores da ALS. Através da técnica “DNA Polimórfico Amplificado ao Acaso” (RAPD), foi possível avaliar as diferenças genéticas entre biótipos de Bidens pilosa resistentes e suscetíveis aos herbicidas inibidores da enzima ALS. Todos os primers analisados amplificaram e apresentaram boa reprodutibilidade das bandas. O coeficiente médio de similaridade genética foi de 43%. Foi observada reduzida similaridade genética entre os genótipos resistentes e suscetíveis aos herbicidas empregados no seu controle. Sendo uma espécie autógama, com significativa taxa de polinização cruzada (10%), a variabilidade genética resultante pode explicar os resultados obtidos e a seleção natural de indivíduos resistentes, quando realizado o uso contínuo de herbicidas com o mesmo mecanismo de ação